Basic Research On Arsenic Removal From White Smoke And Recovery Of Lead, Copper And Zinc

White dust is produced in the pyometallurgical process of roasting,coverting and other process,which collected by solid electric du st removal device.And its elemental composit is more complex.Due to different ore source and smelting process,it generally contains Cu,Zn,Pb,As,Bi,Fe,Ag,Sb and other metal elements.It is a hazardous solid waste.At present,the comprehensive tre atment process of white dust is not perfect in China.Most enterprises are using stockpiling method to treat it.After rain erosion,a large number of toxic and harmful metals enter the groundwater system with the rain water,which causing serious harm to the environment and the human body.Part of the copper smelter will be direct return of white smoke to smelting system,not only decrease the processing capacity of flash furnace,deterioration,and harmful ingredients of As,Pb by cyclic enrichment,it wi ll seriously affect the quality of copper products.In recent years,environmental problems have become increasingly prominent,and the treatment of hazardous solid wastes has become a hot spot of research.In this paper,the mechanism and process of extra ction and separation of Cu,Zn and Pb from white dust were studied.The technological process of extracting metal ions in acid leaching solution was as follows:acid leaching of white smoke with sulfuric acid solution,de-arsenic combined with iron salt-calcium salt,copper replacement with iron powder,Zinc was extracted with P204 and zinc was stripped with sulfuric acid solution.The whole process was feasible and reasonable.Research showed:?1?In white dust,as mainly present in the form of lead arsenate?Pb₂As₂O₆,Pb₂As₂O₇?,zinc arsenate?Zn ₃?As O₄?₂?8H₂O?and arsenic trioxide?As₂O₃?.?2?The soluble substance in the white dust is higher than the hydrogen oxidation system under the sulfu ric acid medium.The optimum conditions of acid leaching of white dust were determined by single factor experiment:reaction temperature 50?,reaction time 30min,liquid-solid ratio 10:1 and sulfuric acid concentration 20%.Under this reaction condition,t he leaching rates of As,Cu,Zn and Pb were 91.63%,94.31%,98.56%and 0.89%,respectively.As,Cu and Zn have good leaching effect.At the same time,Pb can be used in the form of Pb SO ₄ as the lead in the lead ore.?3?Drawing the logarithmic diagram of the concentration of arsenate lg C-H₂O system through thermodynamic data and the theoretical analysis results were verified by single factor experiments,which was consistent with the theoretical analysis.Strictly controlling the p H value of the reaction s ystem can effectively separate of the arsenic from Cu²⁺and Zn²⁺.Through single factor experiment,the best process parameters of iron salt calcium salt combined arsenic removal were obtained,namely reaction time 5h,reaction temperature 85?,p H=1.2,Fe/As?mole ratio?=1.5,no H₂O₂ added.Under this condition,the precipitation rate of arsenic was 89.12%,while Cu and Zn basically did not precipitate.As to scorodite?Fe A s O₄?2H₂O?in the form of removal from acid leaching solution.?4?The key factor affecting the purity of copper in the acid leaching solution after iron removal and arsenic removal was the p H value of the initial system.The effect of p H value on copper replacement was not obvious.However,when the p H value exceeds 1.2,a small amount of As will be coprecipitated.The suitable process conditions were as follows:reaction time 12min,p H=1.2,Fe/Cu?melo ratio?=1.7,reaction temperature was room temperature under this condition,copper replacement rate remained about 94.70%,and the precip itated sediment was mainly Cu and Cu ₂O.?5?P204 has a good extraction effect for Zn.Under the appropriate p H value,Zn²⁺can be selectively extracted and effectively separated from Cu²⁺,Ca²⁺and Fe²⁺.Through experimental research,the best process par ameters were as follows:reaction time 12min,initial p H=2.0,O/A=2.0:1 and P204 concentration 40%,extraction temperature 70?,Zn extraction rate reache ed 96.30%at this condiciont.?6?The reverse extraction agent of zinc was diluted sulfuric acid,and the suitable technological parameters were obtained:stripping time is 6min,reaction temperature is room temperature,O/A=7:1,sulfuric acid concentration is 2.0mol/L,the stripping rate reached more than 99.90%;Zn SO ₄ stripping solution obtained by heating the concentrated natural cooling crystallization of prepare d Zinc sulfate crystals.