Hydrometallurgical Treatment of Waste Printed Circuit Boards: Bromine Leaching
Abstract
:1. Introduction
2. Material and Methods
2.1. Material
2.2. Chemical Analysis Methods
2.3. Mineral Liberation Analysis
2.4. Leaching Tests
3. Result and Discussions
3.1. Sample Characterization
3.2. Bromine Leaching Tests
3.2.1. Effect of Liquid Bromine
3.2.2. Effect of Sodium Bromide
3.2.3. Effect of Selected Acids
- (1)
- The cost of nitric acid is higher than that of hydrochloric acid.
- (2)
- Nitric acid is required to be removed in order to successfully complete the metal recovery by solvent extraction and electrowinning.
3.3. Leaching Kinetics
- Waste printed circuit boards are heterogeneous, leading to other metallic elements reacting with bromine and also, possibly reacting with gold ions. Thus, the mechanism of gold dissolution in the bromine system becomes more complex.
- The diverse presence of gold in the waste printed circuit boards (coating on board surfaces or gold particles in the waste printed circuit boards) also led to the difference of the leaching mechanisms.
- The metals that are more active than gold may reduce gold from gold–bromine complex ions to gold metal, which may further change the leaching mechanism.
- There is also a possibility of a mechanism change as the leaching proceeds.
- In terms of the chemical reaction, three steps may be involved:
- (1)
- Adsorption of bromine and bromide on the gold surface to form AuBr2 [32],
- (2)
- Oxidation of AuBr2− to produce a stable species, AuBr4−,
- (3)
- Copper cementation to reduce AuBr4− to Au0.
4. Conclusions
Supplementary Materials
Author Contributions
Funding
Conflicts of Interest
References
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Material | Element | Vasile et al. 2008 [4] | Hino et al. 2009 [5] | Birloaga et al. 2013 [6] | Yang et al. 2009 [7] | Oishi et al. 2007 [8] | Behnamfard et al. 2013 [9] | Average |
---|---|---|---|---|---|---|---|---|
Organic epoxy resin | C (wt. %) | 24.7 | 18.1 | - | - | - | - | 21.4 |
H (wt. %) | 1.38 | 1.8 | - | - | - | - | 1.59 | |
N (wt. %) | 0.85 | 0.32 | - | - | - | - | 0.59 | |
Br (wt. %) | 4.94 | 5.07 | - | - | - | - | 5.01 | |
Sb (wt. %) | - | 0.45 | - | - | 0.16 | 0.37 | 0.33 | |
Inorganic glass fiber | - | 37.6 | - | - | - | - | 37.6 | |
Cu (wt. %) | 13.8 | 14.6 | 30.6 | 25.1 | 26 | 19.2 | 21.5 | |
Metallic elements | Fe (wt. %) | 1.97 | 4.79 | 15.21 | 0.66 | 3.4 | 1.13 | 4.53 |
Sn (wt. %) | - | 5.62 | 7.36 | 1.86 | 4.9 | 0.69 | 4.09 | |
Ni (wt. %) | 0.17 | 1.65 | 1.58 | 0.0024 | 1.5 | 0.17 | 0.85 | |
Zn (wt. %) | - | - | 1.86 | 0.04 | 2.6 | 0.84 | 1.34 | |
Pb (wt. %) | - | 2.96 | 6.70 | 0.80 | 3.0 | 0.39 | 2.77 | |
Au (ppm) | - | 205 | 238 | - | - | 130 | 191 | |
Ag (ppm) | - | 450 | 688 | - | 630 | 704 | 618 | |
Pd (ppm) | - | 220 | - | - | - | 27 | 124 |
Metal | Market Price Per Unit (USD) | Unit | Average Composition (%) | Market Value Per Tonne of WPCBs (USD) |
---|---|---|---|---|
Gold | 41.5 | g | 0.0191 | 7927 |
Silver | 0.54 | g | 0.0618 | 334 |
Palladium | 32.5 | g | 0.0124 | 4030 |
Copper | 7 | kg | 21.5 | 1505 |
Tin | 20 | kg | 4.09 | 818 |
Fe | 9.5 | kg | 4.53 | 429 |
Lead | 2 | kg | 2.77 | 55 |
Zinc | 3 | kg | 1.34 | 40 |
Nickel | 11 | kg | 0.85 | 94 |
Total market value per tonne of printed circuit boards (USD) | 15,231 |
Reagent | Pros | Cons |
---|---|---|
Sulfuric acid | Highly selective, low reagent cost, well established process for copper ore | At elevated temperature, corrosive |
Chloride | Fast kinetics at room temperature, high solubility and activity of base metals, low toxicity | Excessive corrosion, difficul telectrowinning of copper, poor quality of copper |
Aqua regia | Fast kinetics, effective | High reagent cost, highly corrosive, low selectivity |
Ionic liquids | Thermally stable, environmentally friendly | High cost, excessive dosage |
Reagent | Pros | Cons |
---|---|---|
Cyanide | Highly effective, low reagent dosage and cost | Difficult to process wastewater, environmental risk, low kinetics |
Thiourea | Less toxic, high reaction rate, less interference ions | Poorer stability, high consumption, more expensive than cyanide, downstream metal recovery |
Thiosulfate | High selectivity, non-toxic and non-corrosive, fast leaching rate | High consumption of reagent, downstream metal recovery |
Halide | High leaching rate, high selectivity, relatively healthy and safe except for bromine | Highly corrosive for chlorine, high consumption for iodine |
Aqua regia | Fast kinetics, low reagent dosage | Strongly oxidative and corrosive, difficult to deal with downstream |
Element | Fe (%) | Ni (%) | Cu (%) | Zn (%) | Pb (%) | Sn (%) | Sb (%) | Pd (ppm) | Ag (ppm) | Au (ppm) |
---|---|---|---|---|---|---|---|---|---|---|
Content | 6.3 | 0.5 | 24.1 | 3.3 | 1.1 | 3.8 | 0.3 | 20 | 513 | 145 |
Standard deviation | 0.7 | 0.06 | 1.9 | 0.3 | 0.05 | 0.4 | 0.03 | 2.6 | 46 | 18 |
Phase | Formula | Coarse | Fine | −40 mesh |
---|---|---|---|---|
Copper | Cu | 70.4 | 65.5 | 69.0 |
FeMnZnO | Fe3.5MnZn0.5O3 | 1.13 | 6.33 | 6.65 |
BrCO | (CH2)40BrO6 | 0.67 | 2.15 | 2.82 |
SnBi | Sn0.8Bi0.2 | 3.82 | 2.78 | 1.53 |
BaTiO | BaTiO3 | 0.06 | 1.67 | 1.65 |
PbSn | Pb0.8Sn0.2 | 1.18 | 1.21 | 1.21 |
Carbon_Mix | C10BaSO4 | 0.11 | 0.52 | 0.52 |
BrSbCO | (CH2)40BrO6Sb0.3 | 0.04 | 0.15 | 0.17 |
NdTiO | NdTiO3 | 1.83 | 0.14 | 0.11 |
Fe60Ni40 | Fe0.6Ni0.4 | 1.10 | 0.58 | 0.13 |
Metal | 5 v/v% (0.9 M) H2SO4 Extraction (%) | 15 v/v% (2.7 M) H2SO4 Extraction (%) | 5 v/v% (2.0 M) HCl Extraction (%) | 5 v/v% (1.2 M) HNO3 Extraction (%) |
---|---|---|---|---|
Ni | 95.8 | 93.4 | 95.2 | 94.6 |
Cu | 97.6 | 96.8 | 97.9 | 97.8 |
Zn | 97.2 | 91.7 | 92.5 | 95.8 |
Sn | 98.5 | 99.2 | 96.8 | 97.1 |
Pd | 88.7 | 91.6 | 90.0 | 96.4 |
Ag | 90.0 | 84.8 | 96.5 | 97.2 |
Au | 91.0 | 71.4 | 95.6 | 93.6 |
Metal | Average Extraction (%) | Standard Deviation |
---|---|---|
Ni | 95.21 | 1.81 |
Cu | 97.88 | 0.56 |
Zn | 92.50 | 5.36 |
Sn | 96.79 | 0.44 |
Pb | 97.61 | 0.29 |
Pd | 90.04 | 5.41 |
Ag | 96.52 | 0.79 |
Au | 95.59 | 2.05 |
Br2 (mol/L) | NaBr (mol/L) | Cu (mol/L) | Rate (mmol/L∙min) |
---|---|---|---|
0.388 | 0 | 0.156 | 0.00434 |
0.776 | 0 | 0.156 | 0.00635 |
1.94 | 0 | 0.156 | 0.00751 |
1.94 | 0 | 0.261 | 0.00609 |
1.94 | 0.583 | 0.156 | 0.01244 |
1.94 | 1.166 | 0.156 | 0.01386 |
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Cui, H.; Anderson, C. Hydrometallurgical Treatment of Waste Printed Circuit Boards: Bromine Leaching. Metals 2020, 10, 462. https://doi.org/10.3390/met10040462
Cui H, Anderson C. Hydrometallurgical Treatment of Waste Printed Circuit Boards: Bromine Leaching. Metals. 2020; 10(4):462. https://doi.org/10.3390/met10040462
Chicago/Turabian StyleCui, Hao, and Corby Anderson. 2020. "Hydrometallurgical Treatment of Waste Printed Circuit Boards: Bromine Leaching" Metals 10, no. 4: 462. https://doi.org/10.3390/met10040462
APA StyleCui, H., & Anderson, C. (2020). Hydrometallurgical Treatment of Waste Printed Circuit Boards: Bromine Leaching. Metals, 10(4), 462. https://doi.org/10.3390/met10040462