A novel effective arsenic removal strategy for arsenic-containing gold concentrate: Sulfur retention and arsenic removal by controlled-oxygen roasting

Arsenic-bearing gold concentrate is main raw material used for gold smelting, and arsenopyrite (FeAsS) is a significant proportion of ingredients in gold concentrate. Arsenic removal is an important matter in gold smelting industry. Traditional roasting methods have low arsenic removal efficiency and high costs. In the present study, at first, element contents in gold concentrate were analyzed with X-ray diffraction (XRD), XRD pattern showed that FeAsS and pyrite (FeS 2 ) are main compounds of gold concentrate. Based on XRD data of gold concentrate, roasting reaction mechanisms were deduced through thermodynamic, Gibbs free energy analyses, and thermodynamic equilibrium calculation, and direct oxidation process of FeAsS was concluded into three stages, decomposition, oxidation, and excessive oxidation. Next, condition experiments including roasting temperature, time, atmosphere, and ore quantity were conducted to observe the arsenic removal effect. The results showed that, the controlled oxygen roasting could effectively remove arsenic from gold mineral, and sulfur residue increase in roasted mineral enhanced arsenic removal effect. The removal of arsenic in the decomposition process of pyrite inevitably carried away sulfur, sulfur retention and arsenic removal reactions should be carried out in a neutral or weak reducing atmosphere, and the reaction should be controlled below 700 °C. Finally, condition experiments were summarized as, roasting temperature 700 °C, oxygen 20 vol%, flow velocity 0. 6 ml/min, and time 45 min, with a balance of residue arsenic 0.34 wt% and sulfur 23.5 wt%. In conclusion, retention sulfur united with controlling oxygen is an effective arsenic removal proposal for gold concentrate smelting. A balance of arsenic and sulfur is arsenic 0.34 wt% and sulfur 23.5 wt%. Sulfur retention and arsenic removal roasting is in a neutral or weak reducing atmosphere. Gold ore roasting is carried out in micro oxygen atmosphere, arsenic quickly evaporates in As 2 O 3 . Decomposition temperature of arsenic sulfide in gold ore roasting is 1100 K (823 ℃).