This work was supported by the Ministry of Education, Culture, Sports, Science &#38; Technology and the Ministry of Environment, Government of Japan.

1. Fabrication of Wagon-wheel-shaped, Cubic Ia3d Mesoporous Monolithic Scaffolds
NOTE: Control cubic geometry (preferentially gyroidal Ia3d symmetry) and micrometric particle surfaces of mesoporous monolithic scaffolds by using triblock copolymer Pluronic P123 [P123; poly(ethylene oxide-block-propylene oxide-block-ethylene oxide) (EO20PEO70EO20)] as a template.
<ol>
	<li>Under typical conditions, add P123, pentadecane, and tetramethyl orthosilicate (TMOS) at a mass ratio of 1.6:2:1.2 to HCl/H2O (pH ~1.0) in a 200-ml round-bottom flask; then shake mixture at 45 &#176;C until forming a homogeneous sol-gel.</li>
	<li>Connect flask to a rotary evaporator, and evaporate mixture at 45 &#176;C and a starting pressure of 1,023 hPa. Under these conditions, exothermic hydrolysis and condensation of TMOS occur rapidly.</li>
	<li>Continue evaporation of the mixture for 10-20 min to obtain the optical gel-like wagon-wheel-shaped monolith around the wall of the connect flask 37-39.</li>
	<li>Dry the flask containing the as-made monolith at 45 &#176;C for 24 hr to complete drying process.</li>
	<li>Treat dried wagon-wheel-shaped monolith at 450 &#176;C for 8 hr under normal atmospheric conditions.</li>
	<li>Grind calcined solid monolith completely by using mortar and pestle, and store ground material for later use as a carrier platform in fabrication of MSAs.</li>
</ol>
2. Characterization of Materials
<ol>
	<li>High-resolution transmission electron microscopy (HRTEM)
	<ol>
		<li>Disperse 1 mg of sample in 5 ml ethanol solution using an ultrasonic cleaner, and then drop two droplets of sample on a copper grid.</li>
		<li>Vacuum-dry the grid for 20 min prior to inserting samples in HRTEM column.</li>
		<li>Perform HRTEM using a transmission electron microscope connected to a CCD camera. Record HRTEM micrographs at an acceleration voltage of 200 kV to obtain a lattice resolution of 0.1 nm.</li>
	</ol>
	</li>
	<li>N2 adsorption-desorption isotherms
	<ol>
		<li>Pre-treat wagon-wheel-shaped samples at 100 &#176;C for 8 hr under vacuum to equilibrate pressure to 10&#8722;3 Torr.</li>
		<li>Measure N2 adsorption-desorption isotherms at 77 K using a surface area and pore size analyzer as per the manufacturer&#39;s instructions</li>
		<li>Determine pore size distribution from adsorption isotherms by using nonlocal density functional theory. Calculate specific surface area (SBET) by using multipoint adsorption data from linear segments of the N2 adsorption isotherms using Brunauer-Emmett-Teller (BET) theory.</li>
	</ol>
	</li>
	<li>Small-angle powder X-ray diffraction (XRD)
	<ol>
		<li>Measure XRD patterns by using an 18-kW diffractometer and monochromated CuK&#945; radiation, as per the manufacturer&#39;s instructions.</li>
		<li>Record diffractions by using both a graphite monochromator and G&#246;bel mirror detectors with 2&#952; angles between 0.1&#176; and 6.5&#176;, corresponding to d-spacings between 88.2 and 1.35 nm.</li>
		<li>Grind sample and spread the powder on the sample holder. Confirm resolution of diffraction peaks with standard reproducibility in 2&#952; (&#177;0.005&#176;). Repeat sample measurement three times with rotation at various angles (15&#176;, 30&#176;, and 45&#176;).</li>
	</ol>
	</li>
</ol>
3. Fabrication of Pd(II)-MSA-1, Au(III)-MSA-2, and Co(II)-MSA-3
<ol>
	<li>Synthesis of Pd(II)-MSA-1 and Co(II)-MSA-3 
	NOTE: Use a pressure-assisted method to direct the modification of wagon-wheel-shaped, cubic Ia3d monoliths by 1,5-diphenylthiocarbazone dicarboxylate (L1) and 2-nitroso-1-naphthol (L3) ligands (0.1 M EtOH solutions) to fabricate Pd(II)-MSA-1 and Co(II)-MSA-3, respectively.
	<ol>
		<li>Add ethanolic 1,5-diphenylthiocarbazone dicarboxylate (L1) or 2-nitroso-1-naphthol (L3) solutions to solid wagon-wheel monoliths into round flask and mix under shaking for 1 min.</li>
		<li>Connect flask containing heterogeneous EtOH-L1/solid monolith mixture to a rotary evaporator, and evaporate mixture at 45 &#176;C and a starting pressure of 1,023 hPa.</li>
		<li>Connect another flask containing heterogeneous EtOH-L3/solid monolith mixture to a rotary evaporator, and evaporate mixture at 50 &#176;C and a starting pressure of 1,023 hPa. Remove EtOH solution from heterogeneous EtOH-ligand/solid monolith mixture under vacuum at ambient temperature.</li>
		<li>Clarify the formation mechanism of ligand-solid (MSA-1 and MSA-3) of physisorbed short-range interactions (i.e., van der Waals and H-bonding interactions) between the abundant hydroxyl groups of the active surface sites of the wagon-wheel-shaped scaffolds and the heteroatom ligands 40,41.</li>
		<li>Calculate the amounts of immobilized L1 and L3 as follows: qe =(C0 - Ce )V/m, where qe is adsorbed amount, V is solution volume (L), m is mass of the carriers (g), and C0 and Ce are initial and supernatant probe concentrations, respectively. The amount of immobilized L1 and L3 can be expected to be around 0.09 mmol/g.</li>
	</ol>
	</li>
	<li>Synthesis of Au(III)-MSA-2 
	NOTE: Apply building blocks protocol to synthesize Au(III)-MSA-2:
	<ol>
		<li>Immobilize a 40 ml of 0.1 M ethanol solution of dilauryldimethylammonium bromide (DDAB) into 0.5 g of wagon-wheel-shaped HOM scaffolds using a rotary evaporator to produce wagon-wheel-shaped HOM-DDAB monoliths.</li>
		<li>Dissolve 20 mg of hydrophilic6-hydroxy-5-(4-sulfonatophenylazo)-2-naphthalenesulfonic acid disodium salt (L2) ligand in 80 ml of D.I. water. Add 0.5 g of solid HOM-DDAB monoliths. Then remove the H2O solution through filtration.</li>
		<li>Wash HOM-DDAB-L2 with deionized water until no L2 is eluted; then dry sample at 65-70 &#176;C for 4 hr. Note: 0.07 mmol of L2 ligand per gram of HOM scaffold was incorporated into HOM-DDAB42.</li>
		<li>Clarify the formation mechanism of (MSA-2) based on the L2-DDAB-solid interaction.</li>
	</ol>
	</li>
</ol>
4. Batch Studies for Detecting Pd(II), Au(III), and Co(II) Ions
<ol>
	<li>Immerse 20 mg of wagon-wheel-shaped MSA-1, MSA-2, and MSA-3 in a mixture of Pd(II), Au(III), and Co(II) ions (ion concentration: 2 mg/L); adjust volume to 20 ml and pH to appropriate pH value of 2, 7, and 5.2, respectively.</li>
	<li>Mechanically shake mixtures in a temperature-controlled water bath at 25 &#176;C for 45 min at a constant agitation speed of 300 rpm.</li>
	<li>Filter MSAs through 25-mm filter paper; after equilibration, use visual color assessment and reflectance spectra measurements to determine ion concentrations.</li>
	<li>Determine Pd(II), Au(III), and Co(II) target ion concentrations by comparing reflectance intensities of MSA-1, MSA-2, and MSA-3 at &#955;max 384, 486, and 537 nm, respectively, during the addition of unknown concentration of target samples with those of standard concentration of target samples.</li>
	<li>Conduct other experiments using target Pd(II), Au(III), and Co(II) ion concentrations at the optimum pH value of 2, 7, and 5.2, respectively, using UV-vis spectroscopy. The part per million (ppm, mg/L), part per billion (ppb, &#181;g/L), and molar (mol/L) units are used to define the target ion concentration in solution.</li>
</ol>
5. Method for Removing Pd(II), Au(III), and Co(II) Ions
<ol>
	<li>Immerse 40 mg of each wagon-wheel-shaped MSA in a mixture of specific Pd(II), Au(III), and Co(II) ion concentrations; adjust pH of mixture to specific values of 2, 7, and 5.2, respectively, in a volume of 20 ml, and stir mixture for 2 hr at RT.</li>
	<li>Filter solid MSAs and analyze filtrate by inductively coupled plasma mass spectroscopy (ICP-MS)28-30.</li>
	<li>Calculate the Langmuir isotherm based on the following equation43: 
	<img alt="Equation 1" src="/files/ftp_upload/53044/53044eq1.jpg" /> 
	where Ce is target ion concentration, qe is amount of target ion in equilibrated solution, qm (mg&#183;g-1) is the amount of Pd(II), Au(III), or Co(II) ions removed to form the monolayer coverage, and KL is the Langmuir adsorption equilibrium constant. For instance, the qm data indicate the practical removal of the metal ions from the aqueous medium with high adsorption efficiencies (97%-98%). Moreover, KL values are consistent with the adsorption/desorption rates, indicating fully reversible metal adsorption assays.</li>
</ol>
6. Formation of Metal-to-ligand Binding Constants in Wagon-wheel-shaped MSAs
<ol>
	<li>Determine stability constants (log Ks) of [Pd-(L1)2], [Au-(L2)], and [Co-(L3)2] complexes at pH 2, 7, and 5.2, which can be expected to be around 5.8, 4.9, and 7.9, respectively.</li>
	<li>Calculate stability constants according to the following equation28-32: 
	log Ks = ([ML]S/[L]S) &#215; [M] 
	where [M] is the concentration of free Pd(II), Au(III), or Co(II) ions in solution; [L] represents the concentration of free L (i.e., L not bound to the Pd(II), Au(III), or Co(II) ions); and subscript S refers to the total concentration of the Pd(II), Au(III), or Co(II) ions in the solid phase of the wagon-wheel-shaped MSA.</li>
	<li>Determine limits of detection (LOD) of MSAs for Pd(II), Au(III), and Co(II) ions as follows: 
	LOD = 3&#963;/&#936; 
	where &#963; and &#936; are the standard deviation and the slope of the calibration graph40-42.</li>
</ol>
7. Selective-ion-extraction Experimental System
NOTE: Ensure specific and strong metal-to-ligand binding as follows:
<ol>
	<li>Adjust pH of extracted solution to 2, 7, and 5.2 for the Pd(II), Au(III), and Co(II) ions. Alter concentrations of interfering metal ions to &#8804;5 times greater than the concentrations of the Pd(II), Au(III), and Co(II) target ions. Add a 2 ml of complex-forming agent (e.g., 0.3-0.5 M citrate/tartrate) to the extracted solution prior to the addition of target ions to restrain actively reacting Cu(II) ions.</li>
</ol>
8. Real Extraction of Metals from Urban Mine
<ol>
	<li>Dissolve the PCI board in strong acids to get the metal ions in solution.</li>
	<li>Add MSAs to the solution containing Pd(II), Au(III), and Co(II) ions to extract these ions into solid MSAs.</li>
	<li>Filter solid MSAs and analyze filtrate by ICP-MS.</li>
</ol>

The authors declare that they have no competing financial interests.

Worldwide demand is growing for a means to accurately and rapidly detect, selectively recognize, and recover Pd(II), Au(III), and Co(II) ions from electronic scrap and LIB solutions. To address this issue, wagon-wheel-shaped, optical MSAs for chemical detection/removal/extraction and recovery of these metal ions were developed.
In designing the MSAs, two key factors were considered as follows: (1) receptors and (2) immobilization/transducing scaffolds. Receptors are organic ligands responsible for the selectivity of the MSAs; scaffolds are responsible for the stability, reusability, and sensitivity of the MSAs. Because of their highly uniform channels, large surface areas, pore size distribution, and controllable wagon-wheel structure, which is commonly associated with the [111] projection of the cubic bicontinuous surface morphology (Figures 1 and 2), the MSA-based wagon wheel Ia3d mesostructure material scaffolds provided control over the potential demands of this detection/removal/extraction and recovery method as follows: (1) stability of ligand-embedding HOM solid (i.e., no leaching out of the ligands upon washing), (2) sensing condition assays, and (3) chemical treatment conditions during the regeneration/reuse cycles (i.e., after eight cycles); high ligand-surface coverage and dispersion; mechanical robustness; and efficient recovery processability from urban mine.
To fabricate the stable and robust MSAs design, the monofunctionalization of the wagon wheel inner pore surface or successive inclusion of different ligands (i.e., L1, L2, and L3; Figures 3-5) into the HOM scaffolds can be achieved by pressure-assisted co-condensation; the high-order hybrids MSA-1 and MSA-3 were obtained using L1 and L3, respectively. Controlled design of MSA-2 was based on the fine-tuned surface patterning of the mesoscopic wagon wheel scaffolding architectures. This was accomplished by using a dispersible active agent (DDAB) that led to the dense decoration of L2 signaling centers inside the wagon wheel pore cavities. With these MSA designs, metal ions can interact with organic moieties by noncovalent bonding (e.g., hydrogen bonding), metal coordination, hydrophobic forces, van der Waals forces, &#960;-&#960; interactions, and electrostatic and/or electromagnetic effects (Figures 3-5). In sensing assays, nanoengineered MSAs can be triggered by a target Pd(II), Au(III),or Co(II) ion species and transduce measurable optical signals under synergistic pH, reaction temperature, and contact time (response time) conditions, enabling the binding of the metals into a hydrophobic or hydrophilic ligand pocket to be mimicked. The developed MSAs not only removed Pd(II), Au(III), and Co(II) ions from complex environmental matrices but also provided a means for a simple visual colorimetric estimate of the metal ion concentration; UV-vis reflectance spectroscopy sensitively quantified metal ion concentration over a wide range of concentration (Figures 3-6). Thus, MSAs provide a simple and sensitive colorimetric-based solution to detect changes over a wide range of metal ion concentrations as well as a means for the sensitive quantification of the target ions, thereby avoiding the need for sophisticated instruments. Even at ultra-trace concentrations (&#8804;0.19 &#181;g/L), a signal change in the reflectance spectra of the sensors appeared during formation of the complexes (Figure 1).
In batch sensing/removal/extraction systems, a major advantage of the wagon-wheel-shaped MSAs is their selectivity toward target ions, thereby preventing hindrance from interfering competing ions. Figure 6 confirmed the selective removal and efficient monitoring of Pd(II), Au(III), and Co(II) ions by the optical MSAs. The negligible change in the reflectance signals of the MSAs in the presence of competing ions indicated that weak chelates were formed between competing metals and L1, L2, and L3, specifically at pH 2, 7, and 5.2, respectively. The selectivity of the MSAs can be ascribed to the formation of highly stable octahedral [Pd-(L1)2], square-planar [Au-(L2)], and octahedral [Co-(L3)2] complexes.
For judging the cost-effectiveness, recyclability and durability of wagon-wheel-shaped MSAs after repeated regeneration/reuse cycles were investigated. Figure 8 shows that the MSAs retained a high efficiency for detection/removal/extraction of Pd(II), Au(III), and Co(II) ions over repeated regeneration/reuse cycles, although overall efficiency decreased slightly after the sixth regeneration/reuse cycle. The stability of the cubic Ia3d mesostructure and the incorporation of L1, L2, and L3 into the ordered wagon-wheel-shaped pores (induced by strong H-bonding and dispersive interactions) play significant roles in maintaining the functionality of the ion-sensing/capture system through several regeneration/reuse cycles (see Figure 7).
Recovering Pd(II), Au(III), and Co(II) ions from the urban mine can help limit the environmental damage associated with mining these metals, especially with respect to the impact on land and climate. Using real urban mine samples, results have shown that the MSAs described herein can selectively recover Pd and Au from e-waste, and Co from discarded LIBs (Table 1 &#38; Figure 9), but practical, scalable process still remains challenge for the future applicability of the metal recovery from urban mine.
On the basis of the proposed management protocol, two key components play important roles in the enhanced metal ion accessibility, adsorption capacity, and recovery during the heterogeneous processes. First, the large surface-to-volume ratios and open cylindrical pores of the wagon wheel cubic Ia3d mesostructures (MSAs) promote orientational ligand assembly (as evidenced by the flexible interaction of Pd(II), Au(III), and Co(II) ions with L1, L2, and L3 and the high affinity of the metal-to-ligand binding events) (Figures 3-5). Second, the selective adsorption/detection/extraction processes mainly depend on the structure of the chelating agent, the experimental conditions (particularly pH), the composition of the ion system, the metal ion concentrations, and metal-to-ligand binding events. Although this protocol shows significant progress in the quality, and efficiency of the recovery methods, further efforts are required so that they can be used in other demanding applicability of environmental wastes, in which they enriched with high-doses of actively competitive metals such as Cu(II), Fe(III) and Ni(II) ions.
In conclusion, efficient, cost-effective, wagon-wheel-shaped MSAs have developed for recovering palladium, gold and cobalt metals from the urban mine. Results show evidence that MSAs will be useful in providing a route to a sustainable supply of gold, palladium, and cobalt to meet the needs of modern society.

Driving forces for the booming use of platinum group metals (PGM) are their extraordinary and sometimes exclusive properties, which make them essential components in a broad range of applications. PGMs can play a part in building a sustainable society, and these materials are used in a variety of contemporary applications and products: chemical process catalysis, automotive emissions control, information technology, consumer electronics, fine jewelry, preparation of dental materials, photovoltaic fuel cells, and lithium ion batteries (LIB)1-10. Over the past century, worldwide economic changes have been powered by the use of PGMs. Because of the importance of PGMs in clean technologies and high-technology equipment, the use of PGMs has increased dramatically in modern society. Because of the sharp increases in the use of PGMs, particularly in the production of electronic equipment, the accumulation of electronic waste (e-waste) has led to environmental challenges and concerns. Moreover, the recent surge in commodity prices has generated a new interest in the mining of e-wastes1-4.
E-wastes contain both hazardous materials and valuable palladium, gold and cobalt metals. If e-wastes are disposed of in landfills or not treated in an environmentally sound manner, they may pose a high risk of environmental damage. Palladium, gold and cobalt metals in e-wastes are a sustainable and &#34;green&#34; secondary resource of such metals5-10. Therefore, efficient processes for recovering palladium, gold and cobalt metals from e-wastes are urgently needed.
Future advancements in many technological fields will require control of primary metal resources. Because of the growing importance of palladium, gold and cobalt metals in industrial applications and solutions to environmental problems11-13, developing adsorption/extraction techniques for the recognition and recovery of such metals has become a top priority.
The main precious metals used in electronic products are silver, gold, palladium, platinum, and small quantities of rhodium4-8. Recovering palladium and gold has become crucial because of their unique combination of properties in a wide range of industrial applications, economic value, and rare occurrence. Market mechanisms have been influential in increasing the rates of collection and recycling of circuit boards of outdated PCs, TVs, mobile phones, and other electronic devices. Mass-produced consumer components, such as computer motherboards, contain approximately 80 g of Pd and 300 g of Au per ton of e-waste; the corresponding amounts for mobile phone handsets are 130 g of Pd and 200 g of Au per ton of e-waste5-10. This urban mine holds immense amounts of these metals (by comparison, Au and Pd are present in extremely low concentrations in rocks (~4 ng/g), soils (1 ng/g), seawater (0.05 &#181;g/L), and river water (0.2 &#181;g/L)14-16). To ensure a continuing and reliable supply of palladium, gold and cobalt metals for future technological innovations and new electronic equipment, it is important to develop an efficient and low-cost technology for recycling precious metals from e-waste. Such technology could serve as insurance against a future scarce availability of rare earth ores, which are predicted to be in short supply, or even exhausted, within 100 years.
An element such as cobalt has an essential input to nearly all of the electrochemical storage energy cells such as LIBs17-19. Because of the fast growth of information technology and a wide-range utilization of LIBs, the release of LIBs as e-wastes explored a new environmental challenge18-20. Therefore, handling these wastes with care by recovering these resources might open a new avenue in the environment and industrial applications.
Several powerful and well-established methodologies and analytical techniques have been used to discriminate and quantify Au(III), Pd(II), and Co(II) in natural ore and industrial waste, including flame and carbon furnace atomic absorption spectrophotometry, ultraviolet-visible (UV-vis) spectrophotometry, neutron activation analysis, and inductively coupled plasma mass spectrometry14-16,21-27. Despite their versatility and growing popularity, these analytical techniques suffer from many shortcomings. For example, they usually require careful planning and testing, involve many sample preparation steps to minimize interference from the sample matrix, require sophisticated instrumentation and well-trained individuals, and must be performed under rigorous experimental conditions17,21. Moreover, all of these analytical techniques incorporate pre-concentration and separation steps, such as solvent extraction, coprecipitation, ion exchange, and adsorption, to pre-concentrate the target metal ions from the matrix components prior to their determination20-27. Moreover, hydrometallurgy and pyrometallurgy techniques are commonly used in the recycle chain in industry19-22. Therefore, developing efficient, cost-effective and easy-to-use analytical methods to recover palladium, gold and cobalt metals from natural ore and industrial waste are important both for environmental protection and in the industrial sector11-13.
New technologies can offer new approaches to chemical analysis and recovery of metals from natural ore and industrial waste. Recent progress has been made in reducing the cost and shortening the time to fabricate optical chemical nanosensors/adsorbents; however, optical adsorbents are still used for specific real-world sensing, extraction, and recovery applications for a wide range of metals28-36. Recently, research has focused on tailoring specific solid mesoporous monoliths for use as highly sensitive sensors for the simple and simultaneous naked-eye detection and removal of toxic and precious metal ions, such as mercury and gold ions, from aquatic samples28-32. Here, a process for selectively detecting and efficiently recovering Au(III) and Pd(II) from the urban mine was reported; additionally, the process can be applied for the recovery of Co(II) ions from LIBs. Recycling metals by this process should not only serve as a secondary source of Au(III), Pd(II), and Co(II) ions but also reduce environmental pollution. The protocol designs of wagon-wheel-shaped MSAs show, for the first time, evidence of controlled optical recognition of Au(III), Pd(II), and Co(II) ions, and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes.

<table><tbody><tr><td>Tetramethylorthosilicate (TMOS)</td><td>Sigma&amp;ndash;Aldrich Company Ltd. (USA)</td><td>CAS Number 681-84-5</td><td>Molecular Weight 152.22; Linear Formula Si(OCH&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;4&lt;/sub&gt;; 218472-500G</td></tr><tr><td>Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), PEG-PPG-PEG, Pluronic&amp;reg; P-123</td><td>Sigma&amp;ndash;Aldrich Company Ltd. (USA)</td><td>CAS Number 9003-11-6</td><td>average Mn ~5,800</td></tr><tr><td>Sodium citrate tribasic dehydrate</td><td>Sigma&amp;ndash;Aldrich Company Ltd. (USA)</td><td>CAS Number 6132-04-3</td><td>Linear Formula HOC(COONa)(CH&lt;sub&gt;2&lt;/sub&gt;COONa)&lt;sub&gt;2&lt;/sub&gt; &amp;middot; 2H&lt;sub&gt;2&lt;/sub&gt;O; Molecular Weight 294.10; S4641-500G</td></tr><tr><td>Pentadecane, C15</td><td>Sigma&amp;ndash;Aldrich Company Ltd. (USA)</td><td>CAS Number 629-62-9</td><td>Linear Formula CH&lt;sub&gt;3&lt;/sub&gt;(CH&lt;sub&gt;2&lt;/sub&gt;)&lt;sub&gt;13&lt;/sub&gt;CH&lt;sub&gt;3&lt;/sub&gt;; Molecular Weight 212.41</td></tr><tr><td>&lt;em&gt;N&lt;/em&gt;-cyclohexyl-3-aminopropane sulfonic acid (CAPS)</td><td>Dojindo Chemicals (Japan)</td><td>343-00484, Lot.DE132</td><td>Linear Formula C&lt;sub&gt;9&lt;/sub&gt;H&lt;sub&gt;19&lt;/sub&gt;NO&lt;sub&gt;3&lt;/sub&gt;S, M1254-250G, Molecular Weight 221.32</td></tr><tr><td>2-Nitroso-1-naphthol (NN)</td><td>Tokyo Chemical Industry Con, LTD (TCI)</td><td>Product Number N0267</td><td>Linear Formula ONC&lt;sub&gt;10&lt;/sub&gt;H&lt;sub&gt;6&lt;/sub&gt;OH, M1254-250G, Molecular Weight 173.17</td></tr><tr><td>Sunset Yellow FCF</td><td>Sigma&amp;ndash;Aldrich Company Ltd. (USA)</td><td>CAS Number 2783-94-0</td><td>Empirical Formula (Hill Notation) C&lt;sub&gt;16&lt;/sub&gt;H&lt;sub&gt;10&lt;/sub&gt;N&lt;sub&gt;2&lt;/sub&gt;Na&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;S&lt;sub&gt;2&lt;/sub&gt;, Molecular Weight 452.37, 465224-25G</td></tr><tr><td>Diphenylthiocarbazone</td><td>Sigma&amp;ndash;Aldrich Company Ltd. (USA)</td><td>CAS Number 60-10-6</td><td>Linear Formula C&lt;sub&gt;6&lt;/sub&gt;H&lt;sub&gt;5&lt;/sub&gt;NHNHCSN=NC&lt;sub&gt;6&lt;/sub&gt;H&lt;sub&gt;5&lt;/sub&gt;, Molecular Weight 256.33, 194832-10G</td></tr><tr><td>4-hydrazinobenzoic acid</td><td>Sigma&amp;ndash;Aldrich Company Ltd. (USA)</td><td>CAS Number 619-67-0</td><td>Linear Formula H&lt;sub&gt;2&lt;/sub&gt;NNHC&lt;sub&gt;6&lt;/sub&gt;H&lt;sub&gt;4&lt;/sub&gt;CO&lt;sub&gt;2&lt;/sub&gt;H, Molecular Weight 152.15, 246395-25G</td></tr><tr><td>Carbon disulfide</td><td>Sigma&amp;ndash;Aldrich Company Ltd. (USA)</td><td>CAS Number 75-15-0</td><td>Empirical Formula (Hill Notation) CS&lt;sub&gt;2&lt;/sub&gt;, Molecular Molecular Weight 76.14, 335266-100ML</td></tr><tr><td>Ethanol absolute</td><td>Sigma&amp;ndash;Aldrich Company Ltd. (USA)</td><td>CAS Number 64-17-5</td><td>Linear Formula CH&lt;sub&gt;3&lt;/sub&gt;CH&lt;sub&gt;2&lt;/sub&gt;OH, Molecular Weight 46.07, 24102-1L-R</td></tr><tr><td>Small angle powder X-ray diffraction (XRD)&amp;nbsp;</td><td>Bruker D8 Advance</td><td></td><td>Small angle powder X-ray diffraction (XRD) patterns were measured by using a 18 kW diffractometer (Bruker D8 Advance) with monochromated CuK&amp;alpha; radiation and with scattering reflections recorded for 2&amp;theta; angles between 0.1&amp;#176; and 6.5&amp;#176; corresponding to d-spacing between 88.2 and 1.35 nm. First, the powder samples were ground and spread on a sample holder. The samples were scanned in the range from 2&amp;theta; = 0.1&amp;#176;&amp;ndash;6.5&amp;#176; with step size of 0.02&amp;#176;. To confirm the resolution of the diffraction peaks with standard reproducibility in 2&amp;theta; (&amp;plusmn;0.005), the sample measurement was recorded by using both graphite monochromator and G&amp;ouml;bel mirror detectors. Both detectors were used to generate focusing beam geometry and parallel primary beam. The sample measurement was repeated three times under rotating at various degrees (15&amp;#176;, 30&amp;#176; and 45&amp;#176;).</td></tr><tr><td>N&lt;sub&gt;2&lt;/sub&gt; adsorption&amp;ndash;desorption isotherms&amp;nbsp;</td><td>BELSORP MIN-II analyzer (JP. BEL Co. Ltd)</td><td></td><td>N&lt;sub&gt;2&lt;/sub&gt; adsorption&amp;ndash;desorption isotherms were measured using a BELSORP MIN-II analyzer (JP. BEL Co. Ltd) at 77 K. The pore size distribution was determined from the adsorption isotherms by using nonlocal density functional theory (NLDFT). Specific surface area (SBET) was calculated using multi-point adsorption data from a linear segment of the N&lt;sub&gt;2&lt;/sub&gt; adsorption isotherms using Brunauer&amp;ndash;Emmett&amp;ndash;Teller (BET) theory. Before the N&lt;sub&gt;2&lt;/sub&gt; isothermal analysis, all prepared samples were pre-treated at 100 &amp;#176;C for 8 hr under vacuum until the pressure was equilibrated to 10&lt;sup&gt;&amp;minus;3&lt;/sup&gt; Torr.</td></tr><tr><td>High-resolution transmission electron microscopy (HRTEM)&amp;nbsp;</td><td>JEOL JEM model 2100F microscope</td><td></td><td>High-resolution transmission electron microscopy (HRTEM) was performed using a JEOL JEM model 2100F microscope. HRTEM was conducted at an acceleration voltage of 200 kV to obtain a lattice resolution of 0.1 nm. The HRTEM images were recorded using a CCD camera. In the HRTEM characterization, the sample was dispersed in ethanol solution using an ultrasonic cleaner, and then dropped on a copper grid. Prior to inserting the samples in the HRTEM column, the grid was vacuum dried for 20 min. Energy Dispersive X-ray micro-analyzers (EDX) were recorded by employing Horiba EDS-130S, which directly connected with Hitachi FE-SEM S-4300. Elemental mapping of all samples was carried out with the energy dispersive X-ray micro-analyzers with an acceleration voltage of 30 kV. Ten distinct spots were analyzed per sample, which resulted in 99% confidence bounds of &amp;plusmn;0.01 in the molar fraction of each cation (with their sum normalized to unity).&amp;nbsp;</td></tr><tr><td>UV-Vis-NIR spectrophotometer</td><td>Shimadzu 3700</td><td></td><td>The absorbance spectrum of the nano-collectors material was measured by UV-Vis-NIR spectrophotometer (Shimadzu 3700).</td></tr><tr><td>Inductively coupled plasma mass spectrometry (ICP-MS)</td><td>Perkin Elmer Elan-6000 ICP-MS</td><td></td><td>In selective removal, metal ion concentrations were determined by ICP-AES. The instrument was calibrated using four standard solutions containing 0, 0.5, 1.0 and 2.0 mg/L (for each element) and the correlation coefficient of calibration curve was higher than 0.9999.</td></tr><tr><td>inductively coupled plasma atomic emission spectrometry (ICP-AES)</td><td>PerkinElmer Elan-6000&amp;nbsp;</td><td></td><td></td></tr></tbody></table>

detection and recovery of palladium, gold and cobalt metals from the urban mine using novel sensors/adsorbents designated with nanoscale wagon-wheel-shaped pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Periodic gyroidal cubic Ia3d monolithic scaffolds and wagon-wheel-shaped MSAs with large cylindrical open pores (up to 10 nm in diameter) were fabricated using pressure-assisted direct templating with a P123 copolymer microemulsion system. TEM micrographs of the MSAs show wagon-wheel-like channels organized in large domain sizes and in different orientational geometries in the gyroidal bicontinuous cubic Ia3d mesostructures (Figure 1). Although the L1, L2, and L3 probes were directly physisorbed into the monolithic scaffolds (~80 mg of probe per gram of scaffold), the MSAs provided control over potential leaching out of the ligands upon washing, sensing condition assays, and chemical treatment during regeneration/reuse cycles.
Wagon wheel shape-like pores featured the cubic Ia3d structures of the MSAs, as evidenced by the TEM images (Figure 1). The HRTEM micrographs recorded along the dominant facet in the [111] direction indicate the formation of cubic bi-continuous surface morphology37-39. Six-fold symmetric channels with different nano-sized interconnections in wagon wheel shape-like pores were characteristics the cubic Ia3d lattice structures of MSAs (Figure 1, center)44. Furthermore, the agreement in the unit cell lattice determining by TEM micrographs (22.5 nm) with the unit cell parameter determined by small-angle XRD (a = d211&#8730;6) indicates the formation of the cubic Ia3d MSA morphology.
The appearance of pores of various geometrical shapes in this six-fold orientation around each wagon wheel pattern is the key feature of controlled Pd(II), Au(III), and Co(II) ion diffusion, adsorption, and recovery. Figure 2B indicates that uniformly shaped pore geometries and textural properties of the cubic Ia3d MSA-1, MSA-2, and MSA-3 were retained (surface area (SBET) of 560, 520, and 570 m2/g; pore volume (Vp) of 1.03, 0.98, and 1.09 cm3/g; and pore size (D/nm) of 8.2, 8.1, and 8.2 nm, respectively, as evidenced from N2 isotherm results). This retention of cubic Ia3d MSA structural integrity was used for the rational design of the MSAs, for which the Pd(II), Au(III), and Co(II) ions were detected with a fast response time, even at nanomolar concentrations (Figure 3-5). A sizeable number of organic moieties with potential functional active sites are strongly anchored onto the wagon wheel pore surfaces via H-bonding and dispersive interactions with retention of the cubic Ia3d geometry, as evidenced by the Bragg reflection planes (hkl) (Figure 2A). The formation of stable organic-inorganic hybrid MSAs with suitable accommodation of L1, L2, and L3 into the wagon wheel pores might lead to no leaching of ligands during the metal ion sensing/capture/removal assays and reusability/recovery process.
The specificity and sensitivity of the wagon-wheel-shaped MSAs for the target Pd(II), Au(III), and Co(II) ions were controlled by adjusting the pH to 2, 7, and 5.2, respectively. These specific pH values are the most suitable for the selective, sensitive, and efficient monitoring and removal of metal ions using MSAs (Figure 6A). The quantification procedure for sensing/capturing Pd(II), Au(III), and Co(II) ions with MSA-1, MSA-2, and MSA-3 involved detecting changes in color intensity at color response times (Rt) of 2, 3, and 5 min, respectively. To evaluate the sensitivities of the MSAs, color transitions in the reflectance spectra that could be detected by the human eye were carefully monitored over a wide range of metal ion concentrations (0-5,000 &#181;g/L). Figures 6B-D show changes in color and reflectance intensity of MSA-1, MSA-2, and MSA-3 at &#955;max 384, 486, and 537 nm, respectively. These changes indicate metal-to-ligand binding events during the formation of the octahedral [Pd-(L1)2], square-planar [Au-(L2)], and octahedral [Co-(L3)2] complexes (the stability constants of these complexes are higher than those of competing-ion complexes; Figure 7).The reflectance spectral responses of the MSAs indicated the efficient detection/recognition of metals. In addition, Figure 6F shows that MSAs are very effective in removing and monitoring Pd(II), Au(III), and Co(II) ions from the urban mine and LIB solutions over a wide range of concentrations (from &#181;g/L to mg/L) and even at the low-concentration limits of 0.19, 0.6, and 0.51 &#181;g/L, respectively.
The ion-sensing/ion-removal efficiencies of the wagon-wheel-shaped MSAs toward Pd(II), Au(III), and Co(II) ions in the absence and in the presence of interfering ions were evaluated (Figure 7). Significant changes in the visible color patterns and reflectance spectra were evident, in most cases, upon addition of 1 to 18 competing ions [i.e., (G1) of K(I), Na(I), Li(I), Ca(II), Fe(III), and Cu(II); (G2) of Cd(II), Pb(II), Hg(II), Ni(II), Mn(II), Al(III); and (G3) of Bi(III), Zn(II), Dy(III), Er(III), Ho(III), and La(III)]to the Pd(II), Au(III), and Co(II) ion systems, confirming selective removal and efficient monitoring of the target (T) ions. Low concentrations of Ni(II), Cu(II), and Fe(III) ions interfered, but interferences were eliminated by using 0.3-0.5 M citrate/tartrate solution as a suppressing agent; no signi&#64257;cant changes in the visible color patterns and re&#64258;ectance spectra occurred upon addition of high concentrations of various cations at the optimal ion-sensing/capture conditions (pH 2, 7, and 5.2, 40 mg of the MSAs, 20 ml volume, 25 &#176;C) (Figure 7). These findings indicated selective identification and capture of target ions in a wide range of real samples containing high concentrations of competing ions45,46.
The reusability of the wagon-wheel-shaped MSAs was assessed by examining the reflectance spectra of the target ion sensing/capture assays and determining the uptake efficiency (E %) as a function of regeneration/reuse cycle. The recycling process was carried out by stripping the Pd(II), Au(III), and Co(II) ions from the MSA surfaces (i.e., decomplexation). Decomplexation was accomplished by treating the Pd(II)-, Au(III)-, and Co(II)-MSAs with 0.1 M HClO4, 0.1 M thiourea in 1% concentrated HCl, and 2M HCl, respectively. The decomplexation treatment was carried out repeatedly to completely remove the Pd(II), Au(III), and Co(II) ions from the MSA surfaces. UV-vis spectroscopy and ICP-MS were used to confirm that the MSA surfaces were free of metal (Figure 8). Uptake efficiencies for MSA-1, MSA-2, and MSA-3 were calculated as % (CA/C0), where CA is the target ion concentration uptake by solid MSAs and C0 is the initial target ion concentration. Results indicated that the functionalities of the wagon-wheel-shaped MSAs were maintained over eight regeneration/reuse cycles46,47.
The recovery of Pd(II) and Au(III) from electronic scrap (i.e., PCI boards) and Co(II) from LIBs was carried out in several stages:
The first stage was the mechanical separation of grinded PCI board components.
The second stage included a pretreatment hydrometallurgical process, in which the PCI board chips (e-waste source) were leached in a mixture of 2 M H2SO4 and 0.2 M H2O2 at 90 &#176;C for 6 hr to dissolve base metals (Cu, Fe, Ni, Al, Li, Mn, Co and Zn) and a suspension of partially dissolved plastic and Pd(II) and Au(III) ions8. After filtration of undissolved plastics, the residue was leached with a combined acid of HCl and HNO3 (3:1)at 70 &#176;C for 3 hr to form a soluble solution of Pd(II), Au(III), Ag(I), Fe (III), Sn(IV) and Al(III) ions. The Fe (III), Sn(IV) and Al(III) ions precipitate by raising pH solution up to 4.5 using 2 M NaOH and filtered off. AgCl was precipitated using NaCl and filtered off (Figure 9). Additionally, the LIBs waste components were treated with HNO3, leading to a mixture of Co(II), Ni(II), Mn(II), Li(I), Fe(III), and Al(III) ions.
The third stage involved a series of batch experiments carried out under controlled experimental conditions. In these experiments, leach solutions were purified, Pd(II) and Au(III) ions were recovered from the electronic scrap solutions using MSA-1 and MSA-2 (see Figure 9), and Co(II) was recovered from the main products of the LIB solution using MSA-3 (Table 1). After removal, the filtrate was analyzed by ICP-MS.
In the fourth stage, the percentage uptakes of Pd(II) and Au(III) by MSA-1 and MSA-2 from a real urban mine composite mixture [0.119 mg/L Pd(II), 0.35 mg/L Au(III), 0.23 mg/L Ag(I), 7.05 mg/L Cu(II), 5.78 mg/L Ni(II), 13.35 mg/L Fe(III), 7.09 mg/L Al(III)] were determined. MSA-3 was used to estimate the recovery of Co(II) ions from a real LIB composite mixture [1.75 mg/L Co(II), 420 mg/L Ni(II), 350 mg/L Mn(II), 370 mg/L Li(I), 7 mg/L Fe(III), 1 mg/L Al(III)]. The efficiency of uptake of Pd(II), Au(III), and Co(II) ions by MSA-1, MSA-2, and MSA-3 was calculated as follows: E%= CA/Ce= C0 - Ce/C0, where CA is the target ion concentration uptake by solid MSAs, and Ce and C0 are the target ion concentrations in the equilibrated and initial solutions. Table 1 presents results for the real-sample study of the extraction of Pd(II), Au(III), and Co(II) using the MSAs; the percentage uptakes of Pd(II), Au(III), and Co(II) were approximately 79%, 68%, and 66%, respectively.
The fifth stage involved recovery experiments using stripping agents (Figure 3-5) to release Pd(II), Au(III), and Co(II) ions from the wagon-wheel-shaped MSA surfaces. The recovery efficiency (R%) was calculated as follows: R%= CR/CA, where CR is the target ion concentration released in solution by the stripping agent. ICP-MS analyses of the collected solutions indicated that &#62;&#62;98% of the metal ions were released by simple chemical stripping (Table 1). This result indicates that ultra-trace levels of Pd(II), Au(III), and Co(II) ions were extracted from the urban mine by the MSAs .
<img alt="Figure 1" src="/files/ftp_upload/53044/53044fig1.jpg" /> 
Figure 1. Investigation of wagon-wheel-shaped geometry. HRTEM micrographs of the wagon wheel pattern in the cubic Ia3d structures of the MSAs. Center: crystal shape.
<img alt="Figure 2" src="/files/ftp_upload/53044/53044fig2.jpg" /> 
Figure 2. Determination of mesostructured crystal lattice and surface parameters of wagon-wheel-shaped pores. XRD patterns (A) and N2 adsorption/desorption isotherms (B) of the wagon-wheel-shaped, cubic Ia3d MSAs.
<img alt="Figure 3" src="/files/ftp_upload/53044/53044fig3.jpg" /> 
Figure 3. Systematic engineering of the MSA-1. Fabrication of Pd(II)-MSA-1 and Co(II)-MSA-3 via the pressure-assisted method.
<img alt="Figure 4" src="/files/ftp_upload/53044/53044fig4.jpg" /> 
Figure 4. Systematic engineering of the MSA-3. Fabrication of Co(II)-MSA-3 via the pressure-assisted method.
<img alt="Figure 5" src="/files/ftp_upload/53044/53044fig5.jpg" /> 
Figure 5. Systematic engineering of the MSA-2. Fabrication of Au(III)-MSA-2 via the building blocks protocol.
<img alt="Figure 6" src="/files/ftp_upload/53044/53044fig6.jpg" /> 
Figure 6. Controlled pH-dependent Pd(II), Au(III), and Co(II) ion-sensing systems. (A) pH-response profiles of wagon-wheel-shaped MSA-1, MSA-2, and MSA-3 during the sensing and removal assays of target Pd(II), Au(III), and Co(II) ions. The efficiency of the reflectance spectra was monitored as a function of pH at &#955;max = 384, 486, and 537 nm, respectively. (B-D) Target ion concentration as a function of the reflectance spectra of MSA-1, MSA-2, and MSA-3, respectively. (E) Color maps for the MSAs with addition of 2 ppm Pd(II), Au(III), and Co(II). (F) Calibration plots of (R &#8722; R0) vs. [Mn+] for MSA-1, MSA-2, and MSA-3. Note: R and R0 represent the reflectance of the MSAs with and without the addition of target ions, respectively.
<img alt="Figure 7" src="/files/ftp_upload/53044/53044fig7.jpg" /> 
Figure 7. Study of the Pd(II), Au(III), and Co(II) ion-selective systems. (A-C) Selectivity of wagon-wheel-shaped MSA-1, MSA-2, and MSA-3 toward Pd(II) (2 mg/L), Au(III) (1 mg/L), and Co(II) (2 mg/L) ion-sensing and ion-removal assays. (D) Sequential color response ofMSA-1, MSA-2, and MSA-3 (blank; i.e., metal-free assay) toward target Pd(II), Au(III), and Co(II) ions upon addition of interfering ions in single, binary, and groups of ions (G1-G3).
<img alt="Figure 8" src="/files/ftp_upload/53044/53044fig8.jpg" /> 
Figure 8. Reusability of wagon-wheel-shaped MSAs. (A) Evaluation of the wagon-wheel-shaped, optical sensing/removal assays of the target ions after eight regeneration/reuse cycles (target ion concentration: 2 mg/L; pH and signal response time values for MSA-1, MSA-2, and MSA-3:pH = 2, 7, and 5.2,Rt = 2, 3,and 5 min; t = 25 &#176;C). (B) Uptake efficiency vs. regeneration cycle number.
<img alt="Figure 9" src="/files/ftp_upload/53044/53044fig9.jpg" /> 
Figure 9. Real recovery of Pd(II) and Au(III) ions from electronic scrap solutions. Hydrometallurgical treatment of PCI boards and recovery of Pd(II) and Au(III) ions from electronic scrap solutions.
<table fo:keep-together.within-page="1">
	<tbody>
		<tr>
			<td fo:width="0.45in" width="45">Target ions</td>
			<td fo:width="0.8in" width="120">Target ion-determination</td>
			<td>Target ions (mg/L)</td>
			<td fo:width="4in" width="300">Coexisted metal ions (mg/L)</td>
			<td fo:width="0.3in" width="30">E %</td>
			<td fo:width="0.2in" width="20">R %</td>
		</tr>
		<tr>
			<td rowspan="3">Pd(II)</td>
			<td>C0</td>
			<td>0.119</td>
			<td>Ag (I): 0.23, Au(III): 0.35, Al(III): 7.09, Ni(II): 5.78, Fe(III): 13.35, Cu(II): 7.05</td>
			<td rowspan="3">79</td>
			<td rowspan="3">97</td>
		</tr>
		<tr>
			<td>Ce</td>
			<td>0.025</td>
			<td>Ag (I): 0.225, Au(III): 0.351, Al(III):7.11, Ni(II): 5.77, Fe(III):13.32, Cu(II): 6.95</td>
		</tr>
		<tr>
			<td>CR</td>
			<td>0.0913</td>
			<td>Ag (I): 0.00, Au(III): 0.001, Al(III): 0.00, Ni(II): 0.002, Fe(III): 0.005, Cu(II): 0.009</td>
		</tr>
		<tr>
			<td rowspan="3">Au(III)</td>
			<td>C0</td>
			<td>0.35</td>
			<td>Ag (I): 0.23, Pd(II): 0.119, Al(III): 7.09, Ni(II): 5.78, Fe(III): 13.35, Cu(II): 7.05</td>
			<td rowspan="3">68</td>
			<td rowspan="3">98</td>
		</tr>
		<tr>
			<td>Ce</td>
			<td>0.11</td>
			<td>Ag (I): 0.231, Pd(II): 0.118, Al(III): 7.00, Ni(II): 5.66, Fe(III): 13.29, Cu(II): 6.92</td>
		</tr>
		<tr>
			<td>CR</td>
			<td>0.235</td>
			<td>Ag (I): 0.00, Pd(III): 0.002, Al(III): 0.00, Ni(II): 0.004, Fe(III): 0.003, Cu(II): 0.01</td>
		</tr>
		<tr>
			<td rowspan="3">Co(II)</td>
			<td>C0</td>
			<td>1.75</td>
			<td>Ni(II): 420, Mn(II): 350, Li(I): 370, Fe(III): 2.00, Al(III): 0.40</td>
			<td rowspan="3">66.3</td>
			<td rowspan="3">95</td>
		</tr>
		<tr>
			<td>Ce</td>
			<td>0.59</td>
			<td>Ni(II): 419.34, Mn(II): 350.06, Li(I): 370, Fe(III): 1.91, Al(III): 0.05</td>
		</tr>
		<tr>
			<td>CR</td>
			<td>1.15</td>
			<td>Ni(II): 0.85, Mn(II): 0.00, Li(I): 0.00, Fe(III): 0.05, Al(III): 0.02</td>
		</tr>
	</tbody>
</table>
Table 1. Quantitative determination of metal ions in real samples. ICP-MS analytical data for the recovery of Pd(II), Au(III), and Co(II) ions in electronic scrap and LIB solutions.

Watch this Scientific Journal Video about Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Po

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

detection-recovery-palladium-gold-cobalt-metals-from-urban-mine-using

Universidad de Cartagena UDEC

Research

JoVE Journal

Engineering

28.0K Views.  National Institute for Materials Science, Japan. Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

Video: Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Regeneration of Arrayed Gold Microelectrodes Equipped for a Real-Time Cell Analyzer

The label-free cell-based assay is advantageous for biochemical study because of it does not require the use of experimental animals. Due to its ability to provide more dynamic information about cells under physiological conditions than classical biochemical assays, this label-free real-time cell assay based on the electric impedance principle is attracting more attention during the past decade. However, its practical utilization may be limited due to the relatively expensive cost of measurement, in which costly consumable disposable gold microchips are used for the cell analyzer. In this protocol, we have developed a general strategy to regenerate arrayed gold microelectrodes equipped for a commercial label-free cell analyzer. The regeneration process includes trypsin digestion, rinsing with ethanol and water, and a spinning step. The proposed method has been tested and shown to be effective for the regeneration and repeated usage of commercial electronic plates at least three times, which will help researchers save on the high running cost of real-time cell assays.

This protocol describes a general strategy to regenerate commercial arrayed gold microelectrodes equipped for a label-free cell analyzer aimed at saving on the high running costs ofmicrochip-based assays. The regeneration process includes trypsin digestion, rinsing with ethanol and water, and a spinning step, which enables repeated usage of microchips.

The label-free cell-based assay is advantageous for biochemical study because of it does not require the use of experimental animals. Due to its ability ...

Biochemistry

Microfabrication of Nanoporous Gold Patterns for Cell-material Interaction Studies

Nanostructured materials with feature sizes in tens of nanometers have enhanced the performance of several technologies, including fuel cells, biosensors, biomedical device coatings, and drug delivery tools. Nanoporous gold (np-Au), produced by a nano-scale self-assembly process, is a relatively new material that exhibits large effective surface area, high electrical conductivity, and catalytic activity. These properties have made np-Au an attractive material to scientific community. Most studies on np-Au employ macro-scale specimens and focus on fundamental science of the material and its catalytic and sensor applications. The macro-scale specimens limit np-Au's potential in miniaturized systems, including biomedical devices. In order to address these issues, we initially describe two different methods to micropattern np-Au thin films on rigid substrates. The first method employs manually-produced stencil masks for creating millimeter-scale np-Au patterns, while the second method uses lift-off photolithography to pattern sub-millimeter-scale patterns. As the np-Au thin films are obtained by sputter-deposition process, they are compatible with conventional microfabrication techniques, thereby amenable to facile integration into microsystems. These systems include electrically-addressable biosensor platforms that benefit from high effective surface area, electrical conductivity, and gold-thiol-based surface bioconjugation. We describe cell culture, immunostaining, and image processing techniques to quantify np-Au's interaction with mammalian cells, which is an important performance parameter for some biosensors. We expect that the techniques illustrated here will assist the integration of np-Au in platforms at various length-scales and in numerous applications, including biosensors, energy storage systems, and catalysts.

We report on techniques to micropattern nanoporous gold thin films via stencil printing and photolithography, as well as methods to culture cells on the microfabricated patterns. In addition, we describe image analysis methods to characterize morphology of the material and the cultured cells using scanning electron and fluorescence microscopy techniques.

Nanostructured materials with feature sizes in tens of nanometers have enhanced the performance of several technologies, including fuel cells, biosensors, ...

Bioengineering

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. They offer new possibilities for the characterization of living systems and are particularly appropriate for detecting, localizing and quantifying the presence of metal oxide nanoparticles both in biological specimens and the environment. Indeed, these techniques all meet relevant requirements in terms of (i) sensitivity (from 1 up to 10 &#181;g.g-1 of dry mass), (ii) micrometer range spatial resolution, and (iii) multi-element detection. Given these characteristics, microbeam chemical element imaging can powerfully complement routine imaging techniques such as optical and fluorescence microscopy. This protocol describes how to perform a nuclear microprobe analysis on cultured cells (U2OS) exposed to titanium dioxide nanoparticles. Cells must grow on and be exposed directly in a specially designed sample holder used on the optical microscope and in the nuclear microprobe analysis stages. Plunge-freeze cryogenic fixation of the samples preserves both the cellular organization and the chemical element distribution. Simultaneous nuclear microprobe analysis (scanning transmission ion microscopy, Rutherford backscattering spectrometry and particle induced X-ray emission) performed on the sample provides information about the cellular density, the local distribution of the chemical elements, as well as the cellular content of nanoparticles. There is a growing need for such analytical tools within biology, especially in the emerging context of Nanotoxicology and Nanomedicine for which our comprehension of the interactions between nanoparticles and biological samples must be deepened. In particular, as nuclear microprobe analysis does not require nanoparticles to be labelled, nanoparticle abundances are quantifiable down to the individual cell level in a cell population, independently of their surface state.

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

We describe a procedure for the detection of chemical elements present in situ in human cells as well as their in vitro quantification. The method is well-suited to any cell type and is particularly useful for quantitative chemical analyses in single cells following in vitro metal oxide nanoparticles exposure.

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. ...

Chemistry

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity and convenient colorimetric readout. However, high densities of nanoparticles are typically needed for detection. The available synthesis-based enhancement protocols are either limited to gold and silver nanoparticles or rely on precise enzymatic control and optimization. Here, we present a protocol to enhance the colorimetric readout of gold, silver, silica, and iron oxide nanoprobes. It was observed that the colorimetric signal can be improved by up to a 10000-fold factor. The basis for such signal enhancement strategies is the chemical reduction of Au3+ to Au0. There are several chemical reactions that enable the reduction of Au3+ to Au0. In the protocol, Good&#39;s buffers and H2O2 are used and it is possible to favor the deposition of Au0 onto the surface of existing nanoprobes, in detriment of the formation of new gold nanoparticles. The protocol consists of the incubation of the microarray with a solution consisting of chloroauric acid and H2O2 in 2-(N-morpholino)ethanesulfonic acid pH 6 buffer following the nanoprobe-based detection assay. The enhancement solution can be applied to paper and glass-based sensors. Moreover, it can be used in commercially available immunoassays as demonstrated by the application of the method to a commercial allergen microarray. The signal development requires less than 5 min of incubation with the enhancement solution and the readout can be assessed by naked eye or low-end image acquisition devices such as a table-top scanner or a digital camera.

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

In this work, a protocol for signal enhancement of nanoprobe-based biosensing is presented. The protocol is based on the reduction of chloroauric acid onto the surface of existing nanoprobes that consist of gold, silver, silica or iron-oxide nanoparticles.

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity ...

High Resolution Physical Characterization of Single Metallic Nanoparticles

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single nanometer-scale pore. The signal is characteristic of the molecule&#39;s physicochemical properties and its interactions with the pore. We demonstrate that the nanopore formed by the bacterial protein exotoxin Staphylococcus aureus alpha hemolysin (&#945;HL) can detect polyoxometalates (POMs, anionic metal oxygen clusters), at the single molecule limit. Moreover, multiple degradation products of 12-phosphotungstic acid POM (PTA, H3PW12O40) in solution are simultaneously measured. The single molecule sensitivity of the nanopore method allows for POMs to be characterized at significantly lower concentrations than required for nuclear magnetic resonance (NMR) spectroscopy. This technique could serve as a new tool for chemists to study the molecular properties of polyoxometalates or other metallic clusters, to better understand POM synthetic processes, and possibly improve their yield. Hypothetically, the location of a given atom, or the rotation of a fragment in the molecule, and the metal oxidation state could be investigated with this method. In addition, this new technique has the advantage of allowing the real-time monitoring of molecules in solution.&#160;

Here, we present a protocol to detect discrete metal oxygen clusters, polyoxometalates (POMs), at the single molecule limit using a biological nanopore-based electronic platform. The method provides a complementary approach to traditional analytical chemistry tools used in the study of these molecules.

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single ...

An Efficient Method for Selective Desalination of Radioactive Iodine Anions by Using Gold Nanoparticles-Embedded Membrane Filter

Here, we demonstrate a detail protocol for the preparation of nanomaterials-embedded composite membranes and its application to the efficient and ion-selective removal of radioactive iodines. By using citrate-stabilized gold nanoparticles (mean diameter: 13 nm) and cellulose acetate membranes, gold nanoparticle-embedded cellulose acetate membranes (Au-CAM) have easily been fabricated. The nano-adsorbents on Au-CAM were highly stable in the presence of high concentration of inorganic salts and organic molecules. The iodide ions in aqueous solutions could rapidly be captured by this engineered membrane. Through a filtration process using an Au-CAM containing filter unit, excellent removal efficiency (&gt;99%) as well as ion-selective desalination result was achieved in a short time. Moreover, Au-CAM provided good reusability without significant decrease of its performances. These results suggested that the present technology using the engineered hybrid membrane will be a promising process for the large-scale decontamination of radioactive iodine from liquid wastes.

An efficient method for the rapid and ion-selective desalination of radioactive iodine in several aqueous solutions is described by using gold nanoparticles-immobilized cellulose acetate membrane filters.

Here, we demonstrate a detail protocol for the preparation of nanomaterials-embedded composite membranes and its application to the efficient and ...

A Closed-Type Wireless Nanopore Electrode for Analyzing Single Nanoparticles

Measuring the intrinsic features of single nanoparticles by nanoelectrochemistry holds deep fundamental importance and has potential impacts in nanoscience. However, electrochemically analyzing single nanoparticles is challenging, as the sensing nanointerface is uncontrollable. To address this challenge, we describe here the fabrication and characterization of a closed-type wireless nanopore electrode (WNE) that exhibits a highly controllable morphology and outstanding reproducibility. The facile fabrication of WNE enables the preparation of well-defined nanoelectrodes in a general chemistry laboratory without the use of a clean room and expensive equipment. One application of a 30 nm closed-type WNE in analysis of single gold nanoparticles in the mixture is also highlighted, which shows a high current resolution of 0.6 pA and high temporal resolution of 0.01 ms. Accompanied by their excellent morphology and small diameters, more potential applications of closed-type WNEs can be expanded from nanoparticle characterization to single molecule/ion detection and single-cell probing.

Here, we present a protocol for fabrication of a closed-type wireless nanopore electrode and subsequent electrochemical measurement of single nanoparticle collisions.

Measuring the intrinsic features of single nanoparticles by nanoelectrochemistry holds deep fundamental importance and has potential impacts in ...

Gold Nanoparticle Modified Carbon Fiber Microelectrodes for Enhanced Neurochemical Detection

For over 30 years, carbon-fiber microelectrodes (CFMEs) have been the standard for neurotransmitter detection. Generally, carbon fibers are aspirated into glass capillaries, pulled to a fine taper, and then sealed using an epoxy to create electrode materials that are used for fast scan cyclic voltammetry testing. The use of bare CFMEs has several limitations, though. First and foremost, the carbon fiber contains mostly basal plane carbon, which has a relatively low surface area and yields lower sensitivities than other nanomaterials. Furthermore, the graphitic carbon is limited by its temporal resolution, and its relatively low conductivity. Lastly, neurochemicals and macromolecules have been known to foul at the surface of carbon electrodes where they form non-conductive polymers that block further neurotransmitter adsorption. For this study, we modify CFMEs with gold nanoparticles to enhance neurochemical testing with fast scan cyclic voltammetry. Au3+ was electrodeposited or dipcoated from a colloidal solution onto the surface of CFMEs. Since gold is a stable and relatively inert metal, it is an ideal electrode material for analytical measurements of neurochemicals. Gold nanoparticle modified (AuNP-CFMEs) had a stability to dopamine response for over 4 h. Moreover, AuNP-CFMEs exhibit an increased sensitivity (higher peak oxidative current of the cyclic voltammograms) and faster electron transfer kinetics (lower &#916;EP or peak separation) than bare unmodified CFMEs. The development of AuNP-CFMEs provides the creation of novel electrochemical sensors for detecting fast changes in dopamine concentration and other neurochemicals at lower limits of detection. This work has vast applications for the enhancement of neurochemical measurements. The generation of gold nanoparticle modified CFMEs will be vitally important for the development of novel electrode sensors to detect neurotransmitters in vivo in rodent and other models to study neurochemical effects of drug abuse, depression, stroke, ischemia, and other behavioral and disease states.

In this study, we modify carbon-fiber microelectrodes with gold nanoparticles to enhance the sensitivity of neurotransmitter detection.

For over 30 years, carbon-fiber microelectrodes (CFMEs) have been the standard for neurotransmitter detection. Generally, carbon fibers are aspirated into ...

Quantitative SERS Detection of Uric Acid via Formation of Precise Plasmonic Nanojunctions within Aggregates of Gold Nanoparticles and Cucurbit[n]uril

This work describes a rapid and highly sensitive method for the quantitative detection of an important biomarker, uric acid (UA), via surface-enhanced Raman spectroscopy (SERS) with a low detection limit of ~0.2 &#956;M for multiple characteristic peaks in the fingerprint region, using a modular spectrometer. This biosensing scheme is mediated by the host-guest complexation between a macrocycle, cucurbit[7]uril (CB7), and UA, and the subsequent formation of precise plasmonic nanojunctions within the self-assembled Au NP: CB7 nanoaggregates. A facile Au NP synthesis of desirable sizes for SERS substrates has also been performed based on the classical citrate-reduction approach with an option to be facilitated using a lab-built automated synthesizer. This protocol can be readily extended to multiplexed detection of biomarkers in body fluids for clinical applications.

Quantitative SERS Detection of Uric Acid via Formation of Precise Plasmonic Nanojunctions within Aggregates of Gold Nanoparticles and Cucurbit[n]uril

A host-guest complex of cucurbit[7]uril and uric acid was formed in an aqueous solution before adding a small amount into Au NP solution for quantitative surface-enhanced Raman spectroscopy (SERS) sensing using a modular spectrometer.

This work describes a rapid and highly sensitive method for the quantitative detection of an important biomarker, uric acid (UA), via surface-enhanced ...

Versatile Technique to Produce a Hierarchical Design in Nanoporous Gold

The potential to generate variable pore sizes, simplistic surface modification, and a breadth of commercial uses in the fields of biosensors, actuators, drug loading and release, and the development of catalysts have unquestionably accelerated the usage of nanoporous gold (NPG)-based nanomaterials in research and development. This article describes the process of the generation of hierarchical bimodal nanoporous gold (hb-NPG) by employing a step-wise procedure involving electrochemical alloying, chemical dealloying techniques, and annealing to create both macro- and mesopores. This is done to improve the utility of NPG by creating a bicontinuous solid/void morphology. The area available for surface modification is enhanced by smaller pores, while molecular transport benefits from the network of larger pores. The bimodal architecture, which is the result of a series of fabrication steps, is visualized using scanning electron microscopy (SEM) as a network of pores that are less than 100 nm in size and connected by ligaments to larger pores that are several hundred nanometers in size. The electrochemically active surface area of the hb-NPG is assessed using cyclic voltammetry (CV), with a focus on the critical roles that both dealloying and annealing play in creating the necessary structure. The adsorption of different proteins is measured by solution depletion technique, revealing the better performance of hb-NPG in terms of protein loading. By changing the surface area to volume ratio, the created hb-NPG electrode offers tremendous potential for biosensor development. The manuscript discusses a scalable method to create hb-NPG surface structures, as they offer a large surface area for the immobilization of small molecules and improved transport pathways for faster reactions.

Nanoporous gold with a hierarchical and bimodal pore size distribution can be produced by combining electrochemical and chemical dealloying. The composition of the alloy can be monitored via EDS-SEM examination as the dealloying process advances. The material's loading capacity can be determined by studying protein adsorption onto the material.

The potential to generate variable pore sizes, simplistic surface modification, and a breadth of commercial uses in the fields of biosensors, actuators, ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

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Chapters in this video

Regeneration of Arrayed Gold Microelectrodes Equipped for a Real-Time Cell Analyzer

Microfabrication of Nanoporous Gold Patterns for Cell-material Interaction Studies

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

High Resolution Physical Characterization of Single Metallic Nanoparticles

An Efficient Method for Selective Desalination of Radioactive Iodine Anions by Using Gold Nanoparticles-Embedded Membrane Filter

A Closed-Type Wireless Nanopore Electrode for Analyzing Single Nanoparticles

Gold Nanoparticle Modified Carbon Fiber Microelectrodes for Enhanced Neurochemical Detection

Quantitative SERS Detection of Uric Acid via Formation of Precise Plasmonic Nanojunctions within Aggregates of Gold Nanoparticles and Cucurbit[n]uril

Versatile Technique to Produce a Hierarchical Design in Nanoporous Gold