Selective Cementation of Gold Using an Iron Oxide and Zero-Valent Aluminum Galvanic System from Gold–Copper Ammoniacal Thiosulfate Solutions
Ammonium thiosulfate leaching is a promising alternative to the conventional cyanide method for extracting gold from ores. However, strategies for recovering gold from the leachate are less commercially used due to its low affinity to gold. The present study investigated the recovery of gold from th...
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MDPI AG
2023-07-01
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| Online Access: | https://www.mdpi.com/2075-4701/13/7/1289 |
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| author | Joshua Zoleta Sanghee Jeon Akuru Kuze Nako Okada Ilhwan Park Mayumi Ito Yogarajah Elakneswaran Naoki Hiroyoshi |
| author_facet | Joshua Zoleta Sanghee Jeon Akuru Kuze Nako Okada Ilhwan Park Mayumi Ito Yogarajah Elakneswaran Naoki Hiroyoshi |
| author_sort | Joshua Zoleta |
| collection | DOAJ |
| description | Ammonium thiosulfate leaching is a promising alternative to the conventional cyanide method for extracting gold from ores. However, strategies for recovering gold from the leachate are less commercially used due to its low affinity to gold. The present study investigated the recovery of gold from the leachate using iron oxides (hematite, Fe<sub>2</sub>O<sub>3</sub> or magnetite, Fe<sub>3</sub>O<sub>4</sub>). Cementation experiments were conducted by mixing 0.15 g of aluminum powder as an electron donor and 0.15 g of an electron mediator (activated carbon, hematite, or magnetite) in 10 mL of ammonium thiosulfate leachate containing 100 mg/L gold ions and 10 mM cupric ions for 24 h at 25 °C. The results of the solution analysis showed that when activated carbon (AC) was used, the gold was recovered together with copper (recoveries were 99.99% for gold and copper). However, selective gold recovery was observed when iron oxides were used, where the gold and copper recoveries were 89.7% and 21% for hematite and 85.9% and 15.4% for magnetite, respectively. An electrochemical experiment was also conducted to determine the galvanic interaction between the electron donor and electron mediator in a conventional electrochemical setup (hematite/magnetite–Al as the working electrode, Pt as the counter electrode, Ag/AgCl as the reference electrode) in a gold–thiosulfate medium. Cyclic voltammetry showed a gold reduction “shoulder-like” peak at −1.0 V using hematite/Al and magnetite/Al electrodes. Chronoamperometry was conducted and operated at a constant voltage (−1.0 V) determined during cyclic voltammetry and further analyzed using SEM-EDX. The results of the SEM-EDX analysis for the cementation products and electrochemical experiments confirmed that the gold was selectively deposited on the iron oxide surface as an electron mediator. |
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| spelling | doaj.art-acc681e50a914b1086b517c5ba4d79d72023-11-18T20:30:37ZengMDPI AGMetals2075-47012023-07-01137128910.3390/met13071289Selective Cementation of Gold Using an Iron Oxide and Zero-Valent Aluminum Galvanic System from Gold–Copper Ammoniacal Thiosulfate SolutionsJoshua Zoleta0Sanghee Jeon1Akuru Kuze2Nako Okada3Ilhwan Park4Mayumi Ito5Yogarajah Elakneswaran6Naoki Hiroyoshi7Laboratory of Chemical Resources, Division of Sustainable Resources Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, JapanDepartment of Earth Resource Engineering and Environmental Science, Faculty of International Resources Science, Akita University, Akita 010-0865, JapanLaboratory of Chemical Resources, Division of Sustainable Resources Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, JapanLaboratory of Chemical Resources, Division of Sustainable Resources Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, JapanDivision of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, JapanDivision of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, JapanDivision of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, JapanDivision of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, JapanAmmonium thiosulfate leaching is a promising alternative to the conventional cyanide method for extracting gold from ores. However, strategies for recovering gold from the leachate are less commercially used due to its low affinity to gold. The present study investigated the recovery of gold from the leachate using iron oxides (hematite, Fe<sub>2</sub>O<sub>3</sub> or magnetite, Fe<sub>3</sub>O<sub>4</sub>). Cementation experiments were conducted by mixing 0.15 g of aluminum powder as an electron donor and 0.15 g of an electron mediator (activated carbon, hematite, or magnetite) in 10 mL of ammonium thiosulfate leachate containing 100 mg/L gold ions and 10 mM cupric ions for 24 h at 25 °C. The results of the solution analysis showed that when activated carbon (AC) was used, the gold was recovered together with copper (recoveries were 99.99% for gold and copper). However, selective gold recovery was observed when iron oxides were used, where the gold and copper recoveries were 89.7% and 21% for hematite and 85.9% and 15.4% for magnetite, respectively. An electrochemical experiment was also conducted to determine the galvanic interaction between the electron donor and electron mediator in a conventional electrochemical setup (hematite/magnetite–Al as the working electrode, Pt as the counter electrode, Ag/AgCl as the reference electrode) in a gold–thiosulfate medium. Cyclic voltammetry showed a gold reduction “shoulder-like” peak at −1.0 V using hematite/Al and magnetite/Al electrodes. Chronoamperometry was conducted and operated at a constant voltage (−1.0 V) determined during cyclic voltammetry and further analyzed using SEM-EDX. The results of the SEM-EDX analysis for the cementation products and electrochemical experiments confirmed that the gold was selectively deposited on the iron oxide surface as an electron mediator.https://www.mdpi.com/2075-4701/13/7/1289ammoniacal thiosulfate leachingreductive precipitationgalvanic interactionscyclic voltammetrychronoamperometryiron oxides |
| spellingShingle | Joshua Zoleta Sanghee Jeon Akuru Kuze Nako Okada Ilhwan Park Mayumi Ito Yogarajah Elakneswaran Naoki Hiroyoshi Selective Cementation of Gold Using an Iron Oxide and Zero-Valent Aluminum Galvanic System from Gold–Copper Ammoniacal Thiosulfate Solutions Metals ammoniacal thiosulfate leaching reductive precipitation galvanic interactions cyclic voltammetry chronoamperometry iron oxides |
| title | Selective Cementation of Gold Using an Iron Oxide and Zero-Valent Aluminum Galvanic System from Gold–Copper Ammoniacal Thiosulfate Solutions |
| title_full | Selective Cementation of Gold Using an Iron Oxide and Zero-Valent Aluminum Galvanic System from Gold–Copper Ammoniacal Thiosulfate Solutions |
| title_fullStr | Selective Cementation of Gold Using an Iron Oxide and Zero-Valent Aluminum Galvanic System from Gold–Copper Ammoniacal Thiosulfate Solutions |
| title_full_unstemmed | Selective Cementation of Gold Using an Iron Oxide and Zero-Valent Aluminum Galvanic System from Gold–Copper Ammoniacal Thiosulfate Solutions |
| title_short | Selective Cementation of Gold Using an Iron Oxide and Zero-Valent Aluminum Galvanic System from Gold–Copper Ammoniacal Thiosulfate Solutions |
| title_sort | selective cementation of gold using an iron oxide and zero valent aluminum galvanic system from gold copper ammoniacal thiosulfate solutions |
| topic | ammoniacal thiosulfate leaching reductive precipitation galvanic interactions cyclic voltammetry chronoamperometry iron oxides |
| url | https://www.mdpi.com/2075-4701/13/7/1289 |
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