| In the imperial smelting process(ISP),about 50%arsenic from sintering berden process will be collected in Crude Zinc Oxide of the fuming furnace.Accumulation of arsenic will occur when this Crude Zinc Oxide return to sintering berden process,thus cause adverse effect for production and environment protection.In this article the removal and solidification of arsenic from Crude Zinc Oxide were studied.According to analysis results,arsenic mainly existed as zinc arsenate in the Crude Zinc Oxide,thus the process of "alkaline leaching-lime precipitation-cement solidification" was confirmed,as well as optimum operation conditions.The stability evaluations of cement solidification test block were carried on,too.The optimum operation parameters of the leaching process were as follows:80℃,50 g/L NaOH,L/S mass ratio 3:1,and leaching for 1h.In this process 65～70%arsenic would enter into solution and existed as AsO43-.The precipitation processes were mainly divided into two steps.First, As(Ⅲ) in solution should be oxidized into As(Ⅴ) by hydrogen peroxide. This process was operated at normal temperature,100%As(Ⅲ) would be oxidized when solution was stirred for 0.5h,with 20%hydrogen peroxide excess.Second,As(Ⅴ) was precipitated with Ca(OH)2.At 95℃and with Ca/As mole ratio set at 3:1,99.5%As(Ⅴ) would be precipitated as crystal Ca5(AsO4)3OH when reaction progressed for 2h.After the cement solidification of arsenic calcium,the stability evaluations were carried on,and the results showed that when the Ca-As slag/cement mass ratio was 1:3,test block would satisfy the GB5085.3-2007 standard.When calcinated at 800℃for 1h,Ca-As slag test block become more stable and could satisfy GB5085.3-2007 standard even with 1:1 Ca-As slag/cement mass ratio.
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