Sumitomo Law

Arai Japan Institute proposed Bin "Sumitomo Law", electrolysis can not be obtained pure gold ingot of 99.99%, a yield of more than 98% linear, about half shorten the production cycle. The process flow is shown in Figure 1.

Figure 1 Sumitomo Process

......—has passed trial production

First, control the roasting temperature

The composition of the minerals was analyzed by X-ray diffraction by thermogravimetry and differential thermal analysis and at different heating rates. It was confirmed that the material was easily sintered due to melting of Ag ₂ SeO ₃ (melting point 531 ° C), so the calcination should be slowly increased between 300 and 600 ° C. , the Ag ₂ SeO _{3 is} decomposed. Further, it examined calcine leaching parameters, determining copper, tellurium leaching rate with the concentration of sulfuric acid (100 ~ 250g / L), temperature (40 ~ 80 ℃) temperature increased.

Second, liquid chlorination leaching

Chlorination leaching at 40 ° C, 1h can leach >99% gold. Increasing the temperature and prolonging the time did not change the leaching rate of platinum (64.5% to 68.9%), while palladium increased sharply from 33.9% to 72.4% at 80 °C.

The actual material leaching results, the gold leaching rate is 99.7% ~ 99.8%, (leaching slag containing gold 31 ~ 39g / t), palladium 88.5% ~ 87.1% (200 ~ 211g / t), platinum only 39.6% ~ 36.3% (298 ~ 300g/t), part of selenium and iron are simultaneously leached (49.1% to 51.3% and 60.8% to 62.5%, respectively); copper (14.2% to 12.0%) and arsenic (11.0% to 10.0%) are less; nickel (1.2 %～1.0%), 锑 (0.02%), 铋 (0.1%～0.6%), lead (0.03%～0.02%), and silver does not leaching.

3. The rich gold chlorination solution can be reduced by FeCl ₂ or H ₂ O ₂

For the solution with the composition of Au11.2g/L, Pd0.74g/L and Pt0.19g/L, the reduction is controlled by the oxidation reduction potential of 600~800mV with the concentration of 160g/L FeCl ₂ , and the gold powder is boiled in 1:1 nitric acid for 1h. , plus borax flux refining ingot; powder high purity H ₂ O ₂ reduction. Nitric acid treatment mainly removes silver, palladium and rhodium from gold.

4. After the immersion gold, the platinum and palladium are reduced with formic acid.

Reduction at 80 ° C for 4 h. The stock solution (mg/L) is Au4.2 mg/L, Ag1 mg/L, Pt61 mg/L, Pd 460 mg/L, Fe 2.6 mg/L, pH=1.6 mg/L, and it is preferred to adjust the pH to 4 with NaOH.

The raw material is a dried anode slime after centrifugation. The calcination was carried out in an externally heated rotary cylinder at a temperature of 700 to 750 ° C for 1 h. The sand was ground to 85% to 40 μm and acid leached three times in a 2 m ³ tank. The filtration rate was 9.5 L/m ² ·min at 50 ° C and a pressure of 9.8 to 19.6 × 10 ⁴ Pa, and the filter cake humidity was 22% to 23%.

Chlorine leaching was carried out in a 200 L fluororesin-containing tank with 150 kg of acid leaching residue per batch. Pour 400L chlorine gas leaching solution into 600L glass fiber reinforced plastic tank, heat to 40 °C, adjust pH=1.2, add 22L, 30% concentration of hydrogen peroxide solution, after 2h, solution contains gold 1.8mg/L, final pH and potential respectively About 2 kg of gold powder was obtained for 0.91 and 630 mV. The gold powder is boiled in concentrated nitric acid, and then the flux is melted to melt the ingot. The volume of the immersion gold liquid was adjusted to 450L, and the platinum and palladium were inoculated three times in the chlorine leaching tank (150L solution each time). The condition was: the temperature was 80 ° C, the amount of formic acid was 90%/420, and the pH was started at 4 , stay 2h, the final solution contains Pd1.1mg / L, Pa0.5mg / L, pH = 2, potential 230mV.

The direct yield of gold in each step was: acid leaching >99%, chlorine gas leaching 99%, gold precipitation rate >99.9%, nitric acid treatment >99.9%, and total straight yield estimated over 98%. Since the reduction smelting (production of precious lead), Dole alloy production, palladium electrolysis and gold electrolysis are omitted, the production cycle is less than half of the conventional process.