Sensitivity of Gold Lixiviants for Metal Impurities in Leaching of RAM Printed Circuit Boards
Abstract
:1. Introduction
Leaching Agent | Input Material | Pretreatment | Target Metal | Gold Leaching Yield | Reference |
---|---|---|---|---|---|
0.12 M (NH4)2S2O3 20 mM CuSO4 0.2 M NH₄OH | Scrap and PCBs of waste mobile phones | None | Au | 98% | [19] |
0.2 M (NH4)2S2O3 5 mM CuSO4 0.4 M NH₄OH | RAM sticks | None | Au | >98% | [15] |
60 g/L CH4N2S 4 g/L Fe2(SO4)3 0.1 M H2SO4 | PCBs of spent mobile phones | Crushed and grounded Sieving | Cu, Au | 85.2 ± 0.8% | [20] |
24 g/L CH4N2S 0.6 wt.% Fe2(SO4)3 0.5 M H2SO4 | PCB powder from waste mobile phones | None | Au, Ag | 90% | [32] |
2 g/L I2 12 g/L KI | WPCBs from discarded computers | Shredded Incineration Pressure oxidative acid leaching | Au | >99% | [21] |
1.1% I2 10% KI 1.5% H2O2 | PCB powder from waste computers | Acid leaching | Au | >95% | [33] |
3% I2 1% H2O2 | WPCBs | Acid leaching | Au | 99.98% | [22] |
70 mM C4H4BrNO2 100 mM C5H5N | Pins of waste CPU | None | Au | 60% | [34] |
2. Materials and Methods
3. Results and Discussion
3.1. Material Pretreatment and Characterization
3.2. Base Metal Separation
3.3. Gold Leaching
3.3.1. Parameter Investigation of Lixiviants
- Thiosulfate
- Thiourea
- Iodine–Iodide
- NBS
- Cyanide
3.3.2. Sensitivity of Gold Leaching Lixiviants to Base Metal Content
- Further Investigation of Thiosulfate and ThioureaGold Leaching
4. Conclusions
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
Appendix A
0.2 M CH4N2S | 0.3 M CH4N2S | 0.3 M CH4N2S |
10 mM Fe2(SO4)3 | 5 mM Fe2(SO4)3 | 10 mM Fe2(SO4)3 |
0.1 M H2SO4 | 0.1 M H2SO4 | 0.2 M H2SO4 |
0.4 M CH4N2S | 0.3 M CH4N2S | 0.3 M CH4N2S |
10 mM Fe2(SO4)3 | 20 mM Fe2(SO4)3 | 10 mM Fe2(SO4)3 |
0.1 M H2SO4 | 0.1 M H2SO4 | 0.05 M H2SO4 |
5 mM CuSO4 | 20 mM CuSO4 | 20 mM CuSO4 |
0.2 M (NH4)2S2O3 | 0.2 M (NH4)2S2O3 | 0.2 M (NH4)2S2O3 |
0.2 M NH₄OH | 0.2 M NH₄OH | 0.4 M NH₄OH |
5 mM CuSO4 0.2 M (NH4)2S2O3 0.6 M NH₄OH | 20 mM CuSO4 0.2 M (NH4)2S2O3 0.6 M NH₄OH | 20 mM CuSO4 0.2 M (NH4)2S2O3 0.4 M NH₄OH Reaction time 12 h |
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Trial | Reactant | Temperature | Time | Pulp Density | Stirring Rate |
---|---|---|---|---|---|
BM 1.1 | 2M H2SO4 0.8 M H2O2 | 68 °C | 12 h | 1:20 | 300 rpm |
BM 1.2 | 2 M HCl | 80 °C | 6 h | 1:20 | 400 rpm |
Trial | Reactant | Temperature | Time | Pulp Density | Stirring Rate |
---|---|---|---|---|---|
BM 2.1 | 4 M H2SO4 2 M H2O2 | 35 °C | 24 h | 1:10 | 500 rpm |
BM 2.2 | 5 M HCl | 80 °C | 6 h | 1:10 | 500 rpm |
Leaching System | Reaction Mechanism | Reference |
---|---|---|
Thiosulfate | Anodic half reaction: Au + 2 S2O32− → Au(S2O3)23− + e− Cathodic half reaction: Cu(NH3)42+ + 3 S2O32− + e− → Cu(S2O3)35− + 4 NH3 | [35] |
Thiourea | Anodic half reaction: Au + 2 SC(NH2)2 → Au(SC(NH2)2)2+ + e− Cathodic half reaction: Fe3+ + e− → Fe2+ | [36] |
Iodine–iodide | Dissolution of iodide: I2 + I− → I3− Anodic half reaction: 2 Au + 4 I− = 2 AuI2− + 2 e− Cathodic half reaction: I3− + 2 e− → 3 I− | [37] |
NBS | AuBr4− AuBr4− + Py → PyAuBr3 + Br− | [34] |
Cyanide | Anodic half reaction: Au + 2 CN− → Au(CN)2− + e− Cathodic half reaction: O2 + 2 H2O + 4 e− → 4 OH− | [38] |
Trial | Reactant | Temperature | Time | Pulp Density | Stirring Rate | Reference |
---|---|---|---|---|---|---|
TS 0 | 20 mM CuSO4 0.1 M (NH4)2S2O3 0.2 M NH₄OH | RT | 24 h | 1:25 | 450 rpm | [19] |
TU 0 | 0.8 M CH4N2S 10 mM Fe2(SO4)3 0.1 M H2SO4 | RT | 2 h | 1:25 | 450 rpm | [20] |
I 0 | 8 mM I2 70 mM KI | RT | 4 h | 1:25 | 450 rpm | [21] |
NBS 0 | 20 mM C4H4BrNO2 0.2 M C5H5N | RT | 24 h | 1:25 | 450 rpm | [23,34] |
C 0 | 30 mM KCN 1 mM NaOH | RT | 24 h | 1:25 | 450 rpm | [39,40] |
Chemicals | Producer | Chemicals | Producer |
---|---|---|---|
Sulfuric acid 96% | ITW Reagents | Thiourea 99% | Alfa Aesar |
Hydrogen peroxide 35% | Merck KGaA | Iodine > 99.8% | Sigma Aldrich |
Hydrochloric acid fuming 37% | Merck KGaA | Potassium iodide > 99.5% | Merck KGaA |
Ammonium thiosulfate 98% | Sigma Aldrich | N-Bromosuccinimide 99% | Sigma Aldrich |
Copper(II) sulfate pentahydrate 99% | Alfa Aesar | Pyridine > 99% | Sigma Aldrich |
Ammonia 30% | ITW Reagents | Sodium hydroxide 97% | Sigma Aldrich |
Iron(III) Sulfate x-hydrate 75% | ITW Reagents | Potassium cyanide > 97% | Alfa Aesar |
Au | Ag | Cu | Fe | Al | Ni | Zn | Pb | Sn |
---|---|---|---|---|---|---|---|---|
ppm | ppm | wt.% | wt.% | wt.% | wt.% | ppm | wt.% | wt.% |
785 | 196 | 35.18 | 0.41 | 0.12 | 0.71 | 84.94 | 0.05 | 3.28 |
Cu | Fe | Al | Ni | Zn |
---|---|---|---|---|
63.5% | 100.0% | 88.4% | 88.0% | 100.0% |
Cu | Fe | Al | Ni | Zn | Sn |
---|---|---|---|---|---|
97.7% | 77.2% | 65.0% | 88.3% | 92.5% | 98.0% |
Au | Cu | Fe | Al | Ni | Zn | Pb | Sn | |
---|---|---|---|---|---|---|---|---|
ppm | wt.% | wt.% | wt.% | wt.% | ppm | wt.% | wt.% | |
After the first set of parameters | 1025 | 16.80 | 0.00 | 0.02 | 0.11 | 0.00 | - | - |
After the second set of parameters | 1278 | 1.32 | 0.15 | 0.07 | 0.13 | 10 | 0.08 | 0.11 |
5 mM CuSO4 | 20 mM CuSO4 | |
---|---|---|
0.1 M (NH4)2S2O3 0.2 M NH₄OH | 50.0% | 72.1% |
0.2 M (NH4)2S2O3 0.4 M NH₄OH | 89.4% | 49.0% |
0.3 M (NH4)2S2O3 0.6 M NH₄OH | 86.2% | 85.5% |
0.32 M CH4N2S 10 mM Fe2(SO4)3 0.1 M H2SO4 | 97.0% |
0.8 M CH4N2S 10 mM Fe2(SO4)3 0.1 M H2SO4 | 95.7% |
1.07 M CH4N2S 10 mM Fe2(SO4)3 0.1 M H2SO4 | 82.0% |
8 mM I2 70 mM KI | 21.5% |
12 mM I2 30 mM H2O2 | 29.8% |
8mM I2 70 mM KI 30 mM H2O2 | 31.5% |
20 mM C4H4BrNO2 20 mM C5H5N | 45.3% |
20 mM C4H4BrNO2 100 mM C5H5N | 51.6% |
20 mM C4H4BrNO2 200 mM C5H5N | 41.1% |
30 mM KCN 1 mM NaOH | 65.0% |
80 mM KCN 1 mM NaOH | 66.3% |
150 mM KCN 1 mM NaOH | 77.6% |
Trial | Reactant | Temperature | Time | Pulp Density | Stirring Rate |
---|---|---|---|---|---|
TS 1 | 5 mM CuSO4 0.2 M (NH4)2S2O3 0.4 M NH₄OH | RT | 24 h | 1:25 | 450 rpm |
TU 1 | 0.3 M CH4N2S 10 mM Fe2(SO4)3 0.1 M H2SO4 | RT | 2 h | 1:25 | 450 rpm |
I 1 | 8 mM I2 70 mM KI 60 mM H2O2 | RT | 4 h | 1:25 | 450 rpm |
NBS 1 | 20 mM C4H4BrNO2 0.2 M C5H5N | 40 °C | 24 h | 1:25 | 450 rpm |
C 1 | 150 mM KCN 1 mM NaOH | RT | 24 h | 1:25 | 450 rpm |
Trial | Before Optimized Base Metal Separation | After Optimized Base Metal Separation |
---|---|---|
TS 1 | 89.4% | 96.6% |
TU 1 | 97.0% | 96.4% |
I 1 | 31.5% | 78.9% |
NBS 1 | 58.2% | 55.1% |
C 1 | 77.6% | 95.0% |
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Birich, A.; Gao, Z.; Vrucak, D.; Friedrich, B. Sensitivity of Gold Lixiviants for Metal Impurities in Leaching of RAM Printed Circuit Boards. Metals 2023, 13, 969. https://doi.org/10.3390/met13050969
Birich A, Gao Z, Vrucak D, Friedrich B. Sensitivity of Gold Lixiviants for Metal Impurities in Leaching of RAM Printed Circuit Boards. Metals. 2023; 13(5):969. https://doi.org/10.3390/met13050969
Chicago/Turabian StyleBirich, Alexander, Zixi Gao, Dzeneta Vrucak, and Bernd Friedrich. 2023. "Sensitivity of Gold Lixiviants for Metal Impurities in Leaching of RAM Printed Circuit Boards" Metals 13, no. 5: 969. https://doi.org/10.3390/met13050969
APA StyleBirich, A., Gao, Z., Vrucak, D., & Friedrich, B. (2023). Sensitivity of Gold Lixiviants for Metal Impurities in Leaching of RAM Printed Circuit Boards. Metals, 13(5), 969. https://doi.org/10.3390/met13050969