The Removal Of Fluoride And Chloride From Sulfuric Acid Waste

Smelting process generates a great deal of sulfur dioxide gas, which is mainly used for the production of sulfuric acid. Sulfuric acid waste water was generated in the washing process and acid washing process before the production of sulfuric acid. Its composition is very comples, which mainly contains high concentration of F, Cl, sulfate ions and hevy metals such as Cu, Pb, Zn. Electrical lead dust is an important byproduct produces in the process of lead electorrefining. Its main ingredient is the lead oxide, at the same time, it contains valuable metals including Cu, Fe, Zn, Ag, etal. In this paper, based on the status quo of treatment of fluorine and chlorine, the electrical lead dust was adopted to treat fluorine and chlorine in sulfuric acid wastewater. The main research content and conclusions are as follows:Firstly,based on the properties of sulfuric acid waste and the lead dust,the forms of lead oxide in acidic solution, thermodynamic studies about treatment of fluorine and chlorine using lead oxide revealed that the experimental program is feasible. The theotetical foundation was established to solve the difficult problem of remove fluorine and chlorine from the sulfuric acid waste.Secondly, simulation of sulfuric acid waste which contains fluorine and chlorine was treated by the pure lead oxide, the effects of various parameters which affect the removal efficiency of fluoride and chloride ions in the treatment were studied and the optimum conditions were determined as follows:the concentration of sulfuric acid is1.0mol/L, the reaction time is90min, the L/S ratio is100:35, the reaction temperature is room temperature, the concentration of acetic acid is0.0246mol/L and the stirring speed is400r/min. Under this conditions, the removal efficiency of fluoride and chloride ions are the maximum. The removal efficency of fluoride ions reaches84%, and the removal efficency of chloride ions reachchs93%, and achieves the objectives of removal of fluoride and chloride ions from sulfuric acid solution.Finally, the effects of various parameters in the removing of the fluoride and chloride from sulfuric acid wastewater using the smelting slag-electrical lead dust were studied. And the optimum conditions of the first paragraph of the processing were determined as follows:the L/S ratio is10:4, the concentration of acetic acid is0.2mol/L, the reaction temperature is room temperature and the reaction time is120min, the stirring speed is400r/min and the standing time is60min. Under this conditions, the concentration of fluoride in the supernatant remains about150mg/L, and the concentration of chloride in the supernatant remains about30mg/L.The optimum conditions of the second paragraph of the processing were determined as follows:the L/S ratio is5:1, the concentration of acetic acid is0.14mol/L, the reaction temperature is room temperature and the reaction time is120min, the stirring speed is300r/min and the standing time is60min. Under this conditions, the concentration of fluoride in the supernatant less than50mg/L, and the concentration of chloride in the supernatant less than6mg/L. Afere the second paragraph of processing, the concentration of fluoride and chloride in the effluent can meet the secondary recycling purposes.The results show that it is feasible to remove the fluoride and chloride from sulfate wastewater using the smelting slag-electrical lead dust by two processes.