Alkaline leaching of high arsenic copper concentrate with sodium sulfide-sodium hydroxide for arsenic removal
A kind of high arsenic copper concentrate in Yunnan has a copper grade of 13.46％and an arsenic content of 5.17％.The main minerals are chalcopyrite,pyrite,arsenopyrite,cassiterite,and magnesium aluminum silicate.The alkaline system of sodium sulfide-sodium hydroxide was used to leach the high arsenic concentrate and remove arsenic from the copper concentrate.The effects of process parameters such as sodium hydroxide concentration,sodium sulfide dosage,leaching temperature,rotation speed,liquid-solid ratio,leaching time,etc.on the arsenic removal rate were systematically studied.The results show that the above process parameters seriously affect the removal of arsenic and the alkaline leaching removal rate.The optimal leaching process conditions are:sodium hydroxide concentration of 5 mol/L,sodium sulfide concentration of 50 g/L,leaching temperature of 90 ℃,rotation speed of 1000 r/min,liquid-solid ratio of 10∶1,leaching duration of 3 hours.Under these optimal conditions,a technical index of arsenic removal rate of 60.55％can be finally obtained.Further analysis of alkaline leaching residue using EMPA-EDS revealed that using sodium sulfide and sodium hydroxide alkaline system for leaching can completely dissolve the arsenopyrite in high arsenic copper concentrate.The main arsenic-containing minerals in the leaching residue are zinc sulfide arsenite and arsenite,and the iron hydroxide formed during the leaching process and the iron oxide generated after dehydration cover the surface of arsenic-containing minerals,hindering the sufficient contact between alkaline leaching agents and minerals,which affects the mass transfer efficiency of the leaching process.
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