Comparison of Life Cycle Environmental Impact between Two Processes for Silver Separation from Copper Anode Slime

Abstract

The cost of silver separation is lowered when ammonia and hydrazine hydrate are replaced with sodium thiosulfate and sodium dithionite in the process of extracting of metallic silver from copper anode slime. The overall environmental impact of two types of copper silver separation processes from anode slime has been analyzed\using the LCA method. Through the subdivision analysis, we found the raw materials or emission items that should be improved first. The following conclusions are drawn: (1) The life cycle environmental impact of the sodium thiosulfate process is much lower than the existing process; (2) The resource and environmental impacts of the sodium thiosulfate method are mainly in the fields of climate change, photochemical smog, and ionizing radiation, exceeding two-thirds of the impact on all of the resources and environment; (3) In terms of input and output items, the main impact of the new process on the resources and the environment is concentrated on the use of sodium hydroxide, accounting for 33.98% of the total equivalent, followed by sodium thiosulfate and sodium carbonate, respectively. These input–output items are the key fields that need attention in future technology improvement.

Sustainable Production of Layered Bismuth Oxyhalides for Photocatalytic H2 Production

“…Tellurium, tin, arsenic, and antimony can be removed with the Harris process by mixing in molten NaOH and NaCl. − Other metals are then removed by bubbling in chlorine gas. Once the alloy reaches ∼70% bismuth, desilvering takes place using the Parkes process, a liquid–liquid extraction using molten zinc which extracts any precious metals. ,, Chlorine refining is then continued to achieve >99.99% purity bismuth.…”

“…Once the alloy reaches ∼70% bismuth, desilvering takes place using the Parkes process, a liquid−liquid extraction using molten zinc which extracts any precious metals. 51,59,60 Chlorine refining is then continued to achieve >99.99% purity bismuth.…”