Study On Pretreatment Process Of Ausmelt Copper Smelting Dust To Removal Of Arsenic And Zinc

The dust is the main by-products during the copper smelting process.It contain valuable metal elements such as Pb,Zn,As,Sb,Bi,Cu,etc,which may have certain economic benefits.As the dust can easily floating in the air due to its small particle size,it can lead to seriously pollute the environment and cause bad effects on the health of people.ZnS in the dust keeps the furnace deteriorating.It is of importance to recycle and reuse the dust,improve the utilization rate of mineral resources,which could be of benefit to reduce the pollution to the environment and adhere to the path of the sustainable development.This research was conducted based on the actual production situation of a copper smelting company,and study the optimum leaching parameters under the different conditions for leaching As and Zn from Ausmelt dust and recycling As.The main research contents and conclusions of this paper are as follows:?1?The leaching experiment of Ausmelt dust at atmospheric pressure was carried out in the NaOH system.The effects of the NaOH concentration,liquid-solid ratio,leaching temperature,time and stirring speed on leaching results were investigated.The optimum conditions were as follows:the NaOH concentration was 2mol/L,the liquid-solid ratio was 5mL/g,the leaching temperature was 90°C,the leaching time was1.0h,the stirring speed was 400rpm.Under the optimum conditions,the leaching rates of As,Sb,Pb and Zn were 78.4%,0.27%,17.03%and 8.9%,respectively.?2?In the system of NaOH-Na₂S-H₂O,the leaching experiment of Ausmelt dust at atmospheric pressure was carried out.The concentration of NaOH,the amount ratio of Na₂S/Ausmelt dust,the leaching temperature,the leaching time and the liquid-solid ratio on the leaching results were discussed.The optimum conditions were as follows:the concentration of sodium hydroxide was 2mol/L,the amount ratio of Na₂S/Ausmelt was 1:5,the leaching temperature was 90°C,the leaching time was 1.5h,the liquid-solid ratio was 6:1,and the stirring speed was 300rpm.Under the optimum conditions,the leaching rates of As,Sb,Pb and Zn could up to 91.88%,21.04%,0.57%and 12.95%,respectively.The As in Ausmelt dust was removed and Zn was enriched effectively.By comparing these two methods above,it had a better effect on the leaching of As from Ausmelt dust in the NaOH-Na₂S-H₂O system under the atmospheric pressure.?3?In the NaOH-Na₂S-H₂O system,there was a large amount of As in leaching solution.The As in the leaching solution must be transformed into a stable substance so as to meet the discharge requirement of wastewater containing As.Under the condition that the leaching solution containing As was as the raw material,the effects of pH,Fe/As molar ratio,leaching time and leaching temperature on As were discussed respectively.The optimum process conditions for the precipitation of As by ferric sulfate were as follows:H₂O₂/As=2,pH=5,Fe/As mole ratio=1.5,the leaching temperature was 60°C,the leaching time was 60min,and the stirring speed was 300rpm.Under the optimum conditions,the As deposition rate reached 99.34%.?4?After leaching As in the NaOH-Na₂S-H₂O system,the Zn in alkaline leaching slag mostly exists as ZnS.The HNO₃ concentration,leaching time,leaching temperature and liquid-solid ratio on the leaching effect of Zn were discussed in this experiment.The optimum conditions were as follows:the concentration of HNO₃ was2mol/L,the leaching time was 2h,the leaching temperature was 70°C,the ratio of liquid to solid was 6:1,and the stirring speed was 300rpm.Under these optimum conditions,the leaching rates of Zn,Pb and Sb were 79.92%,9.01%and 1.42%,respectively.?5?In the NaOH-Na₂S-H₂O system,the alkaline leaching residue from the Ausmelt dust was as the raw material.The effects of oxygen partial pressure,H₂SO₄concentration,mass ratio of calcium lignosulfonate/basic leaching slag,leaching temperature and leaching time on the experimental results of oxidic-acidic?H₂SO₄?pressure leaching Zn were discussed.The optimum process conditions were as follows:oxygen partial pressure was 0.5MPa,the concentration of H₂SO₄ was 1mol/L,ratio of lignosulfonate/basic leaching residue was 3‰,leaching temperature was 150°C,leaching time was 2h,stirring speed was 400rpm.Under the optimum conditions,the leaching rates of Zn and Cu were 97.66%and 89.01%,respectively.Compared with the result of Zn leaching in HNO₃ system at atmospheric pressure,it was concluded that the leaching rate of Zn by oxidic-acidic?H₂SO₄?pressure leaching method was higher,and it had less pollution to the environment.