Adsorption Of Au Research Articles

Efficient and selective capture of Au(III) from PCBs by pentaethylenehexamine-modified chloromethylated polystyrene beads.

Recycling of gold promotes solving the problems of resource waste and environmental pollution. In this work, pentaethylenehexamine (PEHA)-modified chloromethylated polystyrene beads (PEHA-CMPS) was synthesized for the recovery of Au(III) from actual printed circuits boards (PCBs) leaching solution. PEHA-CMPS exhibited excellent adsorption efficiency at a wide pH range. It was discovered that the pseudo-second-order and Langmuir model provided a superior match for the Au(III) adsorption process. The maximum adsorption capacity for Au(III) was 1186 mg/g. Furthermore, PEHA-CMPS was able to selectively capture trace Au(III) with recovery efficiencies of above 80% from the actual PCBs leaching solution. In addition, the column separation approach was utilized to better assess the practical applications for PEHA-CMPS, proving that the prepared adsorbent exhibited great prospects in industrial applications. The adsorption efficiency still maintained 95% after five adsorption-desorption cycles. The FTIR, XRD, and XPS analyses demonstrated that Au(III) uptake on PEHA-CMPS was a collaborative process involving electrostatic interaction, chelation, and oxidation-reduction. The PEHA-CMPS provided a promising strategy in Au(III) recovery and environmental remediation.

Functionalized agriculture-derived biomass-based adsorbent for the continuous recovery of gold from a simulated mobile phone leachate

Electronic waste has become a global concern, as it has been steadily increasing over the years. The lack of regulation and appropriate processing facilities has rendered these wastes an environmental hazard. However, they represent excellent alternative sources of precious metals, which are highly in demand in various industries. Adsorption has been a popular method for metal removal/recovery because of several advantages, such as ease of use and low cost. In this regard, it is crucial to develop an inexpensive and functionalized adsorbent to selectively adsorb precious metals. Thus, silica, which is derived from rice husk and is abundantly present in Indonesia, was functionalized using an ionic liquid (SiRH_Im) and used for Au(III) adsorption from a simulated mobile phone leach liquor. SiRH_Im exhibited a high adsorption capacity (232.5 mg g−1). The Au(III) adsorption kinetic suitably fitted with the pseudo-second-order kinetic model. The Au(III) adsorption followed a chemisorption route that suited the monolayer model. Thomas' and Yoon-Nelson's models were well suited for the continuous Au(III) behavior. Selective recovery of Au(III) from SiRH_Im was achieved via sequential desorption. SiRH_Im also showed excellent reusability, as indicated by a negligible decrease in adsorptive performance over three cycles. The functionalization of silica derived from rice husk using an ionic liquid led to the successful creation of a solid adsorbent with a high adsorption capacity toward precious metals present in a simulated leach solution. Our results highlight the benefit of the functionalization of biomass through the immobilization of an ionic liquid toward the enhancement of its adsorption capability.

UV-curable Schiff base-containing polymeric adsorbent for selective and efficient removal of Au(III) from aqueous solutions

UV-curable polymeric adsorbent was prepared using a diacrylate-functionalized hydrazone-oxime monomer (DAFHOM), trimethylolpropane triacrylate (TMPTA), and trimethylolpropane tris(3-mercaptopropionate) (TMPTP) through UV-initiated thiol-ene click reaction. Initially, a novel hydrazone-oxime-based Schiff base ligand was synthesized and modified with diacrylate functionality to prepare the UV-curable polymeric adsorbent. The structures of DAFHOM and the resulting polymeric adsorbent were confirmed using Fourier Transform Infrared Spectroscopy (FTIR) analysis. Additionally, the thermal behavior of the UV-cured adsorbent was investigated through thermal gravimetric analysis (TGA), which revealed that the adsorbent exhibited good stability and did not degrade at room temperature. The adsorption performance of the UV-curable polymeric adsorbent for Au(III) from aqueous solutions was studied under various experimental conditions, including pH, contact time, and initial metal concentration. The UV-curable polymeric adsorbent demonstrated effective and selective Au(III) adsorption from aqueous solutions. The findings indicated that removing Au(III) from water solutions positively correlated with pH, particularly within the pH range of 0.5–2.5. However, the efficiency declined when the pH exceeded 1.5. Among the various adsorption isotherm models investigated, the Langmuir model was found to be the most suitable for describing the behavior of the adsorbent. The maximum adsorption capacity of the adsorbent for Au(III) was determined to be 30.06 mg/g. In batch experiments, the UV-curable adsorbent displayed promising selectivity towards Au(III), even in the presence of competitive ions such as Cu(II), Pb(II), and Cd(II).

Catch and release: Gold adsorption and sorbent electrochemical regeneration

Wastewater generated from e-waste leaching is rich in precious metals including gold, silver and platinum. Conventional precipitation and solvent extraction are chemically intensive separations with concerning environmental externalities. Sorbents, in particular carbon nanotubes, have low chemical consumption, and have shown promise for gold adsorption due to their high specific surface area and chemical functionalization potential. However, regenerating sorbents used to adsorb Au is hazardous requiring strong acids. Herein, we delineate the effect of various functional groups on the sidewalls of multiwall carbon nanotubes (MWCNTs) on gold adsorption, and we introduced an acid-free electrochemical technique for Au elution from MWCNTs. Pristine MWCNTs (P-MWCNTs), carboxylic functionalised MWCNTs (COOH-MWCNTs) and amide functionalised MWCNTs (NH2-MWCNTs) were compared for their affinity for Au adsorption from acidic AuCl4−solutions mimicking acidic e-waste leachate. Au adsorption affinity onto MWCNTs followed the order of P-MWCNT > NH2-MWCNT > COOH-MWCNTs. Au elution from Au-saturated MWCNTs was subsequently achieved up to 65%, using acid-free electrochemical desorption in neutral aqueous brine. The Au electro-desorption was shown to have a direct relationship with both the applied current and the mass of the Au adsorbed on the MWCNTs. This study demonstrates enhanced adsorption-based preconcentration of gold and acid-free regeneration of sorbents.

Post-synthetically functionalized covalent organic frameworks for highly efficient recovery of gold from leaching liquor of electronic waste

Recovery of precious metals from e-waste was of great economic and environmental significance. Herein, the spherical covalent organic frameworks (COF-V) were constructed by the Schiff base reaction between 1, 3, 5-tris (4-aminophenyl) benzene and 2, 5-divinylterephthalaldehyde, followed by post-synthetic modification using mono-(6-mercapto-6-deoxy)-β-cyclodextrin (S-β-CD) and dithiothreitol (DTT) for recovery of gold from e-waste. Multi-farious microscopic and spectroscopic techniques were used to explore the micromorphology and elemental composition of all the materials. Meanwhile, the response surface method was used to optimize the experimental parameters to improve the adsorption performance of Au(III). The functionalized spherical COFs exhibited excellent Au(III) adsorption abilities with maximum adsorption capacities of 652.6 mg/g and 820.8 mg/g for COF-V-DTT and COF-V-S-β-CD, respectively. The impressive properties were due to the synergistic adsorption effect of the grafted hydroxyl and sulfhydryl groups in appropriately sized ordered pores. The spectral analysis demonstrated that Au(III) was firstly adsorbed on the adsorbents by coupling with the S atom, and then in situ reduced to Au(0) by hydroxyl groups. Moreover, two COFs materials also exhibited an excellent selectivity in the actual gold-containing waste liquid. Thus, this study would provide an efficient and economical way to recovery Au(III) from wastewater.

Efficient and selective recovery of gold and palladium by simple and easily synthesized polyethylenimine based polymer

Polyethylenimine (PEI) crosslinked by 5,5-dithiodisalicylic acid (TDSA) is prepared through solution polymerization and serves as an adsorbent (TDSA@PEI) for the effective adsorption of Au(III) and Pd(II). TDSA@PEI exhibits excellent adsorption performance for Au(III) in a wide pH range of 3–10. The maximum adsorption capacity of TDSA@PEI for Au(III) and Pd(II) is 2579 mg/g and 808 mg/g at 25 °C, respectively. The adsorption isotherms of the two precious metals by TDSA@PEI are more fitted well by the Langmuir model. Meanwhile, TDSA@PEI exhibits excellent selectivity and reusability for Au(III) and Pd(II) adsorption. The adsorption equilibrium was reached at 5 min for 9.8 mg/L of Pd(II), and the adsorption kinetics of both Au(III) and Pd(II) are in accordance with the pseudo-second-order kinetic model. The adsorption of Au(III) and Pd(II) by TDSA@PEI is a spontaneous, endothermic and entropy increasing process. In addition, the column separation approach proves the great applicability of TDSA@PEI in industry. The abundant amino, thioether and hydroxyl groups in TDSA@PEI are responsible for its superior performance, forming several types of interactions with Au(III) and Pd(II) ions such as electrostatic interactions, chelation and redox.

Fast and Selective Adsorption of Au (III) from the Waste Printed Circuit Boards Using a Low-Cost Adsorbent: Optimization by Central Composite Design Based on Response Surface Methodology

A low-cost new green adsorbent (GA) was synthesized by tannin-rich pomegranate peel powder and formaldehyde for the fast and selective recovery of Au (III). It was characterized by Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET), elemental analysis (CHN), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) (FE-SEM-EDS-mapping). The optimal values of influential factors were defined using a central composite design based on the response surface methodology (CCD-RSM). Adsorption properties were investigated by the kinetic, isotherm, thermodynamic, and interference of coexisting metal ions at optimum conditions. The experimental adsorption percentage with three repetitions under the optimized conditions such as pH = 2, adsorbent mass = 23 mg, Au (III) concentration = 32 m g L − 1 , and contact time = 30 min was 97% and the highest adsorption capacity of the GA was 315.450 m g g − 1 . The adsorption isotherm and kinetic were clarified by the Freundlich (R2 = 0.952) and pseudo-second-order (R2 = 0.998) models. The thermodynamic study (∆S° > 0, ∆H° > 0, and ∆G° < 0) revealed that Au (III) adsorption via GA was a facile, endothermic, and spontaneous process. The adsorption mechanism could be an electrostatic interaction and reductive adsorption. A small amount of GA (23 mg) adsorbed gold selectively and rapidly (30 min) from coexisting metals present in the waste printed circuit board (PCB) such as Ag, Al, Si, Zn, Pb, Ba, Ni, Ca, Mo, Co, Cr, Mn, Cu, Mg, Fe, and W. These results confirm the use of low-cost and high-efficiency GA to fast and selectively recover gold from waste PCBs.

Experimental and molecular modeling investigation on adsorption of gold cyanide complex onto the iron oxide and hydroxide minerals

Complex and refractory gold ores contain high amount of iron oxide and hydroxide minerals, potential adsorbents of gold through preg-robbing phenomenon. In this study, density functional theory (DFT) approach was used to investigate the adsorption of Au(CN)2- complex on hematite, magnetite, and goethite surfaces. The most stable adsorption occurred for goethite when the Au(CN)2- complex was adsorbed from the Au atom along the y axis on the Fe site and the interaction energy was the highest. The following trend was obtained for the preg-robbing potential, which is in good agreement with experiments carried out on synthetic minerals: Goethite > Hematite > Magnetite.

Hyperbranched polyethyleneimine functionalized porous polyacrylonitrile/graphene oxide nanofiber membrane for adsorption and reduction of Au(III)

Hyperbranched polyethyleneimine functionalized porous polyacrylonitrile/graphene oxide nanofiber membrane for adsorption and reduction of Au(III)

Enhanced adsorption selectivity of Au(III) over Cu(II) from acidic chloride solutions by chitosan/palm kernel fatty acid distillate/magnetite nanocomposites

This work aimed to develop a modified chitosan adsorbent with enhanced adsorption selectivity for Au(III) over Cu(II) from acidic chloride solutions using low-cost and green raw materials. Various adsorbents, i.e., chitosan powder, chitosan microbeads, chitosan/palm kernel fatty acid distillate (PKFAD) microcomposites, magnetite nanoparticles, and chitosan/PKFAD/magnetite nanocomposites (CPMNs), were first evaluated for their ability to adsorb Au(III) and Cu(II) from single- and binary-metal solutions across different pH levels, followed by parametric analysis of Au(III) and Cu(II) adsorption from binary- and multi-metal solutions onto CPMNs, Au(III) desorption from Au(III)-loaded CPMNs, and reusability of CPMNs. Finally, Au(III)-loaded CPMNs were characterized with SEM-EDX, XRD, FTIR, and XPS to confirm the proposed adsorption mechanisms. Among all the adsorbents studied, CPMNs exhibited outstanding performance in adsorbing Au(III) from an equimolar binary Au(III)-Cu(II) solution, achieving the highest equilibrium adsorption capacity of 0.479 mmol/g (94.4 mg/g) without reaching saturation. Under optimal adsorption conditions of pH 3, 1 g/L CPMN dosage, and 90 min contact time, CPMNs adsorbed 96 % of Au(III) with a selectivity over Cu(II) exceeding 99 %. CPMNs demonstrated excellent reusability, maintaining over 80 % adsorption and desorption efficiencies for 5 cycles. The proposed adsorption mechanisms of CPMNs for Au(III) encompass electrostatic attraction, hydrogen bonding, solvation, and reduction.

Cr-based metal–organic frameworks (MOFs) with high adsorption selectivity and recyclability for Au (Ⅲ): Adsorption behavior and mechanism study

Preparation of efficient adsorbents is of great significance for the recovery of precious metals from secondary resources. Herein, –NH2 was successfully grafted on MIL-101(Cr) via hydrothermal reaction to improve the adsorption capacity of Au (Ⅲ) in aqueous solution. MIL-101(Cr)–NH2 had a huge specific surface area (1016.50 m2‧g−1), which can provide more adsorption sites for Au (III). At 298 K, the maximum adsorption capacity of Au (III) by MIL-101(Cr)–NH2 was 792.43 mg∙g−1 and was higher than that by MIL-101(Cr) (140.83 mg∙g−1). The adsorption data was well fitted by Langmuir and pseudo-second-order models, confirming that the adsorption process conformed to single molecule adsorption and chemical adsorption. Mechanism study indicated that the adsorption of Au (III) by MIL-101(Cr)–NH2 was initiated with electrostatic attraction and promoted by reduction and inner complexation between AuCl4- and protonated amino groups. During adsorption, Au (Ⅲ) was reduced to Au (0) and Au (I) by –NH2. Density functional theory (DFT) calculation demonstrated that MIL101(Cr)–NH2 possessed higher binding affinity and more adsorption sites for Au (III) than MIL-101(Cr). Moreover, MIL-101(Cr)–NH2 exhibited excellent selectivity towards Au (III) and good recyclability, which is promising in the recovery of precious metals.

Facile synthesis of thiolated silica-encapsulated magnetic adsorbents: Effective adsorption and rapid separation of Au(Ⅰ) from thiosulfate solution

It is important to develop a facile and highly efficient synthetic strategy to fabricate an adsorbent exhibiting excellent adsorption performance and separation ability to recover Au from thiosulfate solutions. Herein, we report a magnetic silica composite (Fe3O4 @SiO2-SH) that was successfully fabricated using an economical, one-pot synthesis method for efficient Au(I) adsorption. The results revealed that the performance of the adsorbent was pH dependent, and the single saturated adsorption capacity was 15.11 mg/g. The adsorption process could be well-explained by the Elovich kinetic model and Langmuir isotherm model, indicating that chemical adsorption dominated the monolayer adsorption process. Furthermore, the adsorption process was exothermic. The chemical structures and properties of the adsorbents were analyzed using various characterization and analysis methods. The chelating interaction between -SH and Au(I) promoted the adsorption of Au on Fe3O4 @SiO2-SH. The gold-loaded, highly reusable adsorbent could be readily eluted using Na2S2O3 (3 mol/L), and > 90% of the gold could be recovered from the adsorbent in a thiosulfate gold leaching solution with Cu2+-NH3-S2O32- as the leaching system. Most of the adsorbent in the pulp could be collected using a magnet, and this reduced the separation cost. The adsorbent can recover more than 90% of gold in both simulated and actual thiosulfate-based gold leaching solutions, indicating that the results reported herein provide a cost-effective strategy for the fabrication of magnetic silica composites characterized by a satisfactory adsorption capacity.

A novel PAN/GO electrospun nanocomposite fibrous membranes with rich amino groups for highly efficient adsorption of Au(III)

The wastewater containing Au(III) is directly discharged into the natural environment, resulting in a serious waste of resources and pollution of water environment. Therefore, it has profound significance to efficiently remove and recover Au(III) from industrial wastewater. Hyperbranched polyethyleneimine (HPEI), as a non-toxic polymer, rich in primary and secondary amine groups, which have strong affinity for metal ions. However, the application of HPEI as an adsorbent in water system is limited by the fact that it is water-soluble and difficult to separate and recover. In this study, using graphene oxide (GO) grafted with HPEI as additive and polyacrylonitrile (PAN) as matrix, PAN/GO-HPEI electrospun nanocomposite fibrous membranes were synthesized by electrospinning, and then grafted with HPEI by chemical graft reaction to obtain HPEI-g-PAN/GO-HPEI electrospun nanocomposite fibrous membranes, which were employed as adsorbent to adsorb Au(III) in aqueous solution. Benefitting from the existence of rich amino groups in the HPEI-g-PAN/GO-HPEI, the HPEI-g-PAN/GO-HPEI had highly efficient adsorption for Au(III) and the maximum adsorption capacity was 2893.33 mg·g−1. Significantly, the adsorbed Au(III) could be reduced to Au(I) and irregular flakes and granular Au elemental attached to the adsorbent in the adsorption process. Moreover, the HPEI-g-PAN/GO-HPEI had excellent adsorption selectivity for Au(III). Therefore, the HPEI-g-PAN/GO-HPEI has potential applications as a promising adsorbent for highly efficient recovery of Au(III) in wastewater.

Synthesis of covalent thiourea organic polymer (CTOP) and adsorption of au (III) ions

Synthesis of covalent thiourea organic polymer (CTOP) and adsorption of au (III) ions

Electrochemical interfaces between Au(100) and deep eutectic solvents: An in situ scanning tunneling microscopy study

Deep eutectic solvents (DESs) are promising electrolytes for electrochemical fields due to their excellent properties. Electrochemical behaviors of Au(100) electrode in two choline chloride-based DESs ethaline and reline with different hydrogen bond donor molecules have been investigated by cyclic voltammetry and in situ scanning tunneling microscopy (STM). Cyclic voltammograms present three pairs of current peaks for Au(100) electrodes in the two DESs. On the basis of the results of in situ STM, the three pairs of current peaks are assigned to the formation and lifting of Au(100) surface reconstruction, adsorption and desorption of chloride ions, and phase transition of chloride ion adlayer. Compared with Au(111), one extra current peak and the corresponding (√5 × √5)R26.6° ordered adlayer of chloride ions were observed for Au(100) electrode. An order-order phase transition of chloride ion adlayer was observed in ethaline, while an order-disorder phase transition was observed in reline. Furthermore, no Au islands was observed on Au(100) surface in ethaline after the lifting of reconstruction when the potential is moved positively and gradually. However, gold nanowires could form and stably exist on Au(100) surface, which are different from that formed on Au(111) surface in reline. Our results provide detailed insights into the interfacial structures between Au(100) electrode and DESs on the atomic scale that hydrogen bond donor molecules and the surface crystallography of the electrode interface could significantly affect the arrangement of gold atoms of the electrode surface and chloride ions in the innermost Stern plane.

Suppression of TS-1 Aggregation by Freeze-Drying to Enhance Au Dispersion for Propylene Epoxidation Using H2 and O2

Au particles immobilized on uncalcined TS-1 (i.e., TS-1-B) have emerged as highly active catalysts for propylene epoxidation using H2 and O2 owing to their good stability. However, it is challenging to enhance the dispersion of Au due to the limited exposed Ti sites for Au adsorption. In this work, we develop a simple method to improve the dispersion of Au particles by employing freeze-dried TS-1-B as a support. Compared with the generally used oven-drying method, the freeze-drying technology can significantly enhance the dispersion of TS-1-B particles, thus giving a small contact angle (indicating good wettability), which is beneficial to achieving the uniform adsorption of Au precursors on TS-1-B, hence forming highly dispersed Au particles. Thus, the as-prepared Au/TS-1-B catalyst shows a significantly improved propylene oxide (PO) formation rate (ca 240 gpo·h–1·kgcat–1) together with high PO selectivity (ca 92%) and hydrogen efficiency (ca 41%).

Aminophosphonic acid derivatized polyacrylonitrile fiber for rapid adsorption of Au(S2O3)23– from thiosulfate solution

A fast and efficient Au (I) recovery adsorption method from an actual leaching solution of Cu2+-en-S2O32- is presented. Aminophosphonic acid derivatized polyacrylonitrile fibers (PAN-NP), prepared with triethylenetetramine and phosphoric acid by chemical grafting, were used as the adsorbent. The adsorbent was well characterized by FT-IR, SEM, TGA and XPS. The effects of contact time, pH, temperature, and Au (Ⅰ) concentration were also investigated. PAN-NP can rapidly capture Au(S2O3)23– (20 min) and has a maximum adsorption capacity of 14.68 kg/t. Compared with -SH modified, PAN-NP has better stability and without oxidized. The adsorption process was described based on the Langmuir isothermal model (R2 > 0.99). Thermodynamic parameters indicated that the adsorption of Au(S2O3)23– on PAN-NP was exothermic (ΔHθ = −9.906 kJ/mol) and adsorption mechanism involved a collective effect resulting the anion exchange of Au(S2O3)23– with –RNH3+H2PO3-, electrostatic attraction between –RNH3+ and Au(S2O3)23– and complexation of P = O with Au (Ⅰ). Besides, PAN-NP-Au can be effectively eluted by sodium sulfite. Importantly, in the Cu2+-en-S2O32- actual leaching solution, the PAN-NP can efficiently recover Au (I) with an adsorption percentage of up to 97 % at a the solid­liquid ratio of 1:50, thereby affording a satisfactory application result. This is a meaningful method for recovering Au (Ⅰ) from thiosulfate solution.

Highly efficient and selective recovery of Au(III) by cellulose microspheres bearing nucleobase and their applications in gold slag treatment

Gold recovery from secondary resources involves tremendous environmental and economic implications. In this work, four nucleobase (guanine, xanthine, hypoxanthine and adenine) modified cellulose microspheres were synthesized via radiation method for Au(III) capture from actual gold slag solution. The adsorption rapidly achieved equilibrium within 4 h. It was discovered that the pseudo-second-order and Langmuir model provided a superior match for the Au(III) adsorption process on adsorbents. At the optimal pH, the four adsorbents exhibited the outstanding adsorption capacities for Au(III) with a range of 307.69–510.20 mg/g. Furthermore, cellulose microspheres bearing nucleobase were able to selectively adsorb trace Au(III) with recovery efficiencies of 62 %–70 % from gold slag leaching solution. In addition, the column separation approach was utilized to better assess the applicability of adsorbents, proving that cellulose microspheres bearing nucleobase exhibited great benefits and prospects in industrial applications. The N-containing groups on adsorbents captured Au(III) by ion exchange, chelation and oxidation–reduction. The low-cost nucleobase-bearing adsorbents offer a new prospect for nucleobase in environmental remediation and water treatment.

Selective gold recovery from pregnant thiocyanate leach solution using ion exchange resins

Gold leaching using thiocyanate in acidic media is an alternative to cyanidation which is less toxic and can be done sequentially in one system without further preparation such as neutralization after acidic (bio)oxidation. Previous research activity in gold-thiocyanate leaching and gold recovery from thiocyanate pregnant leach solution (PLS) is limited. The current study deals with the selective recovery of gold over copper from synthetic and real thiocyanate PLS using ion exchange resins. Consequently, selective adsorption of Au(I) by ion exchange resins and selective Au(I) elution by proper eluent is proposed to obtain a high-purity Au(I) solution. First, the functionality of MTA 5011 and Amberjet 4200 resins at ambient temperature, and pH 2 for 24 h shaking at different resin mass (g) to PLS (L) ratios with synthetic PLS was compared. Then, 100 g/L MTA 5011 was chosen as the optimum resin/PLS (g/L) ratio for the highest separation with 99% gold and 12% copper extraction. Moreover, it was observed that over 24 h adsorption by 100 g/L MTA 5011, the copper extraction decreased, causing an increase in gold adsorption. Among the different reagents that were employed for gold elution, a solution of 0.01 M thiourea (TU) and 0.1 M H2SO4 was the most efficient with 70% gold and 4% copper elution. Adsorption experiments with MTA 5011 were repeated on the original thiocyanate PLS obtained after pyrite biooxidation and thiocyanate leaching using 0.2 M NaSCN and 0.01 M Fe3+. It was determined that the adsorption using 100 g/L MTA 5011 extracted ca. 99% gold and 5% copper, and for elution, a mixed solution of 0.01 M TU and 0.1 M H2SO4 recovered 99.2% gold and < 1% copper which validated the results from the synthetic PLS.

A novel S,N-rich MOF for efficient recovery of Au(III): Performance and mechanism

A novel S,N-rich MOF with adenine and 4,4′-thiodiphenol as organic ligands was synthesized via the one-step solvothermal method, and used for gold recovery. The pH impact, adsorption kinetics, isotherms, thermodynamics, selectivity, and reusability were investigated accordingly. The adsorption and desorption mechanism were also explored comprehensively. The electronic attraction, coordination, and in situ redox account for the Au(III) adsorption. The Au(III) adsorption is affected strongly by the pH of solutions, and best at pH of 2.57. The MOF exhibits exceptional adsorption capacity as high as 3680 mg/g at 55 °C, fast kinetics with 8 min for 9.6 mg/L Au(III), and excellent selectivity for gold ion in real e-waste leachates. The adsorption process of gold on the adsorbent is endothermic and spontaneous, and influenced visibly by temperature. The adsorption ratio still maintained 99% after seven adsorption-desorption cycles. The column adsorption experiments show that the MOF has outstanding selectivity for Au(III) with 100% of removal efficiency in a complex solution containing Au, Ni, Cu, Cd, Co, and Zn ions. A glorious adsorption with a breakthrough time of 532 mins was obtained for the breakthrough curve. This study not only provides an efficient adsorbent for gold recovery, but also guidance for designing new materials.