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Dusts from furnaces for pyrometallurgical refining of copper (Cu) in which arsenic (As) was pre-removed through the use of vacuum carbothermal reduction methods could be used as raw materials. After treating the As pre-removed dusts through oxidative leaching using waste acids, the process of neutralizing and precipitating As and iron (Fe) in the leaching solution was investigated, as well as the precipitation and stabilization process of As and Fe residues. The results show that the leaching rate of Cu, Zn, and As from such dusts can reach 98.98%, 97.46%, and 95.22%, respectively, after leaching operation with waste acids under a liquid–solid ratio of 8:1, a leaching temperature of 80°C, an airflow rate of 300 ml/min, and a leaching time of 120 min. When the molar ratio of Fe to As (n(Fe)/n(As)) is 1.50 in the solution after advanced oxidization, and the final pH value of neutralization is 2.0, the precipitation rate of As and Cu in the residues as ferric arsenates is 93.65% and 2.2%, respectively. As and Fe are neutralized and precipitated, which allows Cu to enter the solution, while As enters the residues. After being transformed, the unstable As and Fe residues can be stockpiled as nontoxic, stable waste. [ABSTRACT FROM AUTHOR]

A combination of waste acid leaching and CaO roasting methods was investigated to recover copper from refining slags of copper fire anode furnace and other valuable metals. The influences of the leaching temperature, leaching time, liquid-solid ratio, and airflow rate on the recovery rates of Cu, Fe, and As were separately evaluated during the leaching process. The roasting temperature, roasting time, and CaO-slag ratio on the removal rates of Cu, Fe, and As were also investigated during the CaO roasting process. The results show that at a leaching temperature of 90 ℃, the liquid-solid ratio of 9:1, leaching time of 4 h, and an airflow rate of 200 mL/min, the leaching rates of Cu, Fe, and As could reach 85.32%, 68.41%, and 44.97% respectively during the waste acid was directly leached from the refining slags of copper fire anode furnace. After leaching, the slags were mixed with CaO under conditions involving a roasting temperature of 800 ℃, roasting time of 4 h, and a CaO-slag ratio of 5.1. After baking, sands were again leached by waste acids: the leaching rate of Cu in baking sands reached 87.05%. The final recovery rates of Cu, Fe, and As could reach 98.10%, 69.60%, and 50.48% respectively. [ABSTRACT FROM AUTHOR]

Removal of arsenic using the low-temperature vacuum carbothermal reduction method was investigated by taking dusts with high contents of arsenic and copper from furnaces for pyrometallurgical refining of Cu as raw materials. Based on TGA-DSC, differential thermal analysis was applied to the raw materials; by virtue of various methods including XRD, ICP, and SEM: the phases, chemical compositions and morphologies of dusts and evaporation residues were separately analysed; on the basis of thermodynamic analysis, the influences of the evaporating temperature, residual pressure, reductant dosage, and evaporation time on the removal rates of As and other valuable metals were explored. The results show that at an evaporating temperature of 350 °C, the residual pressure of 100 Pa, reductant dosage of 25%, and evaporation time for 50 min, the As removal rate can reach 93.48% while guaranteeing that the other metals are essentially not evaporated. This realises the selective separation of As from the other valuable metals. The evaporation products are higher-purity As 2 O 3 , which can be used as a primary As 2 O 3 product. The valuable metals are concentrated in evaporation residues, being conducive to subsequent recovery by leaching with waste acids. • As removal rate can reach 93.48% while realising the effective separation of As from the other valuable metals. • The evaporation products are high-purity As 2 O 3 , which can be used as a primary As 2 O 3 product. • The valuable metals are concentrated in evaporation residues, being conducive to subsequent recovery. [ABSTRACT FROM AUTHOR]