Study On Treatment And Recovery Process Of Acidic Heavy Metal Wastewater

China's water resources are scarce,and more and more attention has been paid to the reuse of industrial wastewater after treatment,but the reuse of chlorine-containing sulfuric acid heavy metal wastewater is difficult.To solve this problem,a joint process is planned to separate heavy metal ions in acid heavy metal wastewater,remove Cl^-,and recover sulfuric acid.This research can not only play a role in protecting the ecological environment,but also turn waste into treasure,which has important practical value.The main research results are as follows:?1?A monovalent selective cation exchange membrane electrodialysis method was used to separate heavy metals in acid heavy metal wastewater.The experiment investigated the influence of current density,flow rate,voltage and acidity on the separation efficiency of H⁺,Zn²⁺and Cd²⁺.The results show that under the condition of acidic heavy metal wastewater acidity of 5%,and initial concentrations of Zn²⁺and Cd²⁺of 20 mg/L and 5 mg/L,its treatment effect is best when the optimal current density of the electrodialysis unit is 25 mA/cm²,the suitable inlet flow rate of the fresh water chamber and concentrated water chamber is 15 L/h,and the running time is 168 min.Under the optimal conditions for the operation of the electrodialysis unit,the H⁺transmission rate in the fresh water chamber reaches 85%,and the leakage rates of Zn²⁺and Cd²⁺both reach 12.86%.?2?After separation of heavy metals by electrodialysis,since the acidity of the recovered liquid is lowered,the recovered liquid needs to be concentrated to increase its acidity.The experiment also investigated the treatment effect of the concentrated recovery solution by electrodialysis and vacuum membrane distillation.The results show that the electrodialysis method was not suitable for concentrating the acid recovery liquid,and the vacuum membrane distillation method concentrated the acid recovery liquid with good effect.Under the condition that the recovery liquid has an acidity of 3%,and Cl^-and SO₄^2-concentrations of 812.64 mg/L and 61.88 g/L,its treatment effect is best when the cold side vacuum is 0.097 MPa,the feed liquid flow is18L/h,the feed liquid temperature is 62°C,and the running time is 2 h.At this time,the membrane flux reached 7.17 L/?m²·h?,and the acidity was concentrated 5.49 times.?3?After concentrating the recovery liquid through vacuum membrane distillation,in order to recover sulfuric acid,a chlorine removal test is required.The experiment also investigated the treatment effect of monovalent selective anion exchange membrane electrodialysis to separate Cl^-and SO₄^2-and electrolysis to remove chlorine.The results show that,according to the water quality of this experiment,the separation of Cl^-and SO₄^2-by electrodialysis is inferior,and the removal of chlorine by electrolysis has a good effect.Under the conditions that the recovery liquid has an acidity of 6.5%,and Cl^-and SO₄^2-concentrations of 2 g/L and 152.29 g/L,its treatment effect is best when the current density is 60 mA/cm².At 30 minutes of electrolysis,the Cl^-removal rate was92.39%.?4?After the above experimental research,it was finally determined to use the combined process of"electrodialysis separation of heavy metals+vacuum membrane distillation method of concentrated recovery liquid+electrolytic dechlorinationl"for treatment and recovery of acidic heavy metal wastewater.