Along with copper, the excavated ore layers usually additionally include arsenic, which, because of its toxicity, must be extracted from the ore. This takes place virtually mechanically when the ore is heated: The arsenic turns into gasoline. In Chile, the present process is to seize the gasoline, dissolve it in sulfuric acid after which remodel it into strong calcium arsenate or calcium arsenite via precipitation. These calcium compounds are then deposited within the Atacama Desert.
The truth that these compounds are water-soluble hasn’t been an issue for the reason that Atacama Desert is without doubt one of the driest areas on this planet. Nevertheless, lately, local weather change has induced a rise in rainfall, which now raises the difficulty of environmental contamination. On the similar time, some mines are penetrating layers which can be now not oxygen-based however sulfur-based and thus include extra arsenic. In consequence, the quantity of arsenic to be deposited will enhance sooner or later, notably on condition that there are at present no industrial makes use of for arsenic.
“These two developments are actually making Chilean mine operators rethink the best way through which they beforehand disposed of arsenic and adapt to those new circumstances immediately,” Anna-Lisa Bachmann, who coordinates the ‘ReAK—Discount of Arsenic in Copper Concentrates’ venture, stated in a media assertion. “We’re investigating new methods of separating and depositing the arsenic as a part of this venture in order that the environmental influence is minimized as a lot as attainable.”
totally different choices
Since 2019, Bachmann and her workforce have seemed into a number of totally different potential course of steps, beginning with the additional processing of arsenic-rich copper focus and together with arsenic-selective flotation, sulfation roasting, and microbial and sulfidic leaching.
Various oxidation processes leading to extra secure and fewer poisonous arsenic5+ compounds as an alternative of unstable and water-soluble arsenic3+ compounds are additionally being thought-about.
“One choice for this oxidation step may very well be the usage of hydrogen peroxide, however that is very costly,” Bachmann stated. “This is the reason we at Fraunhofer IWKS are investigating electrochemical oxidation with diamond electrodes as a viable various in the midst of this venture. They function a very massive electrochemical window, ensuing within the formation of hydroxyl radicals in aqueous options. These then oxidize the dissolved arsenic effectively and reliably with out the necessity for extra chemical compounds.”
Different venture companions are additionally evaluating UV- and ozone-assisted in addition to microbial oxidation processes.
Step one of all work packages is to check whether or not the strategy in query really works and whether or not it delivers the specified outcome. Fraunhofer IWKS will examine their cost-effectiveness and environmental influence within the context of life cycle evaluation and life cycle costing analyses as quickly as all the particular person outcomes can be found.
“We are going to use this to develop a brand new idea for landfilling that may present beneficial actions to the Chilean authorities, contemplating each governmental necessities and the obtainable monetary assets,” Bachmann famous.
That is notably related on condition that a lot of Chile’s copper trade, together with one of many mines collaborating within the venture, is state-owned.