Arsenic removal from arsenic-containing copper dust by vacuum carbothermal reduction-vulcanization roasting

Arsenic-containing copper dust is a typical solid hazardous waste generated from the copper smelting pyrometallurgical process. It has become one of the key factors restricting to hinder the sustainable development of copper pyrometallurgical enterprises owing to its potential environment threat, although containing considerable value metals besides arsenic. In this study, we propose a novel process of vacuum carbothermal reduction-vulcanization roasting to remove arsenic. In the stage of vacuum carbothermal reduction, the arsenic in arsenate was reduced and volatilized, and partial arsenic was reduced to form intermetallic compounds with other metals, which inhibited the further removal of arsenic, resulting in 70% arsenic removal in the reduction stage. The arsenic in reduction slag was removed by following sulfur roasting and the roast slag with below 1% arsenic was recycled. The overall arsenic removal rate is 95% higher, and major metals such as lead, bismuth, copper, and tin in the sample were deposited in the slag. Most of the arsenate and metal arsenide in the dust, such as Cu3As and FeAs, were eventually transformed into volatile arsenic and arsenic trioxide. The proposed novel process has a remarkable effect on the separation of arsenic in arsenic-containing copper dust with complicated composition and has certain application prospects.