Call us now:
Recycling of precious metals by wet leaching process: step-by-step leaching and recovery of precious metals from electronic waste. The pretreated electronic waste is thermally decomposed at 400°C to remove organic matter in waste printed circuit boards and pastes. Then use 9mol/LHNO to leach Ag, CuO, CdO and other oxides, filter, and immerse the liquid to collect and recover silver. Gold, platinum, palladium, etc. remain on the circuit board, and are recovered separately after leaching with aqua regia.
Concentrated nitric acid can also be used to leach matrix metal and silver in electronic waste, while Au, SnO2sPdC, etc. are not dissolved. After filtering, the filter residue is leached with aqua regia. After filtering and washing, dibutyl carbitol can be used to extract and recover gold from the filtrate. Or treat the suspension with concentrated sulfuric acid, filter, the filter residue is Au, SnOz and PbSO4, add soda ash to smelt and recover gold. The filtrate is replaced with copper to obtain a silver alloy with a palladium content of 34%, and the electrolysis of the Ag-Pd alloy can produce silver and platinum respectively. The recovery rates of silver, aluminum, gold and copper are all greater than 97%.
The technical process of leaching electronic waste with nitric acid, and retrieving platinum and silver by precipitation of xanthate and NaCl respectively.
The waste circuit board contains: PdO131%, Cu4.2%, Sn2.2%, Pb3.3%, Ag0.92%, and others are ceramic chips. The liquid-solid ratio is 1:1, leaching with 25% HNO3 at room temperature for 4 hours, about 95% of platinum and silver enter the immersion solution, and about 4% of palladium remains in the leaching residue:, the filtrate is precipitated with xanthate for platinum, salt for silver, After purification treatment, palladium sponge with a palladium content of 99.98%, a palladium recovery rate of 96% and silver powder with a silver content of 99% and a silver recovery rate of 93% can be obtained. The nitric acid leaching residue is mainly SnO2, which is leached with hydrochloric acid, and the leaching solution is replaced with zinc powder to recover platinum.
The hardened waste silver glue (conductive silver paste containing 75%-77% silver) produced by the electronics and instrument factory can be treated by burning-nitric acid leaching-sodium chloride sinking silver-formaldehyde and ammonia water reduction process, which can produce Pure silver powder with a silver content greater than 99% is produced, and the silver recovery rate is not less than 97%.
