Study On Curing Of Arsenic Sulfide Slag By Slag - Based Low Temperature Ceramic Cementitious Material

Arsenic, a chemical metalloid element which is thiophil, is mainly associated with non-ferrous metal mines. There are a amount of Arsenic compounds in Arsenic residues, which are pose a high risk to human health and ecological environment. In order to figure it out, a great deal of effort have been made, but most have little effects or cause high costs, So we desperately need a workable method to this problem. This paper starts on properties of arsenic sulfide residue, then arsenic sulfide residue was solidified by using chemically bonded ceramics prepared with slag, and with optimizing, arsenic sulfide residue was stably solidified. studies have showed that:(1)Arsenic leaching was influenced by pH of leaching liquid, Ca/As, Si/As and CO32-/As, pH of leaching liquid and Ca/As are main factors. When pH of leaching liquid was less than12, the concentration of arsenic leaching decreased with increasing of pH of leaching liquid, the concentration of arsenic leaching increased rapidly when pH of leaching liquid more than12; It is complicated that Ca/As works on arsenic sulfide residue system, it depends on which one is main factor between dissolution reaction and precipitation reaction in solution.(2) Arsenic sulfide residue is easily soluble in alkali, however, cements and chemically bonded ceramic materials’s hydration will generate lots of OH-, so arsenic sulfide residue was not able to solidify until being pretreatment.(3) As in arsenic sulfide residue became relatively stable calcium arsenate by pretreating with lime, then being solidified by chemically bonded ceramics. Through calculation and experiments, the best pretreament condition were the ratio (the lime to arsenic sulfide residue, wt/wt) of0.8.(4)After optimizing, effect of chemically bonded ceramics became better than before. The optimum ratio is:20%of Silicate activator,4%of desulphurization Gypsum,10%of fly ash,9%of mineral activator,57%of slag. With using this ratio, arsenic sulfide residue by pretreatment below20%, high arsenic residue below30%and arsenic calcium residue below40%were stably solidified in nomorl curing-pressure. (5)In FC、NS、PG、AP and hydrogen peroxide, only FC and hydrogen peroxide were beneficial to solidification,1～1.5%of FC and0.5-1%of hydrogen peroxide could be added in solidification process.(6)XRD and SEM showed that there were no crystalline arsenic compounds in solidified body, which meant arsenic had changed to be non-crystalline substances that were stable, structure of solidified body, almost like high temperature melt, was dense and highly cemented to each part.(7)It would take7.7515million yuan to hand capacity of10thousand tons per year by chemically bonded ceramics prepared with slag, however,12.075million yuan was needed by using cement, obviously, chemically bonded ceramics prepared with slag is much better than cement in arsenic sulfide residues.