The Application Of Efficient Treatment For High-salt Wastewater Containing Heavy Metals From A Lead And Zinc Smelter In Yunnan Province

The smelting industry dominated by lead and zinc is one of the main sources of heavy metal-containing wastewater,and the environmental problems brought about by it have also attracted people's attention.In the treatment of such wastewater,traditional chemical precipitation methods,such as lime neutralization precipitation method is generally adopted by enterprises.However,the neutralization of lime method is various defects,such as large consumption of chemicals,large amount of sludge production,and insufficient water output.However,the heavy metal chelate agent can deepen the treatment of heavy metal ions in wastewater based on the traditional chemical precipitation method.This method lays a foundation for realizing the“zero discharge”and reusing of heavy metal ions and in industrial smelting wastewater.This study takes the smelting wastewater of a lead-zinc smelter in Yunnan province as the object,and uses two heavy metal chelating agents?HDTC,XCBY?which developed in the laboratory to strengthen the removal effect of Pb²⁺,Zn²⁺,Cd²⁺and Mn²⁺in the smelting wastewater by the lime neutralization and precipitation method.The results are as follows:?1?The optimum dosage and pH for treating heavy metal smelting wastewater with HDTC,XCBY by single factor experiment:the pH 10 and dosage 6mg/L are for HDTC.And the residual concentrations of Pb²⁺,Zn²⁺,Cd²⁺and Mn²⁺in wastewater are 0.063 mg/L,0.69 mg/L,0.097 mg/L,1.38 mg/L,respectively;when adding XCBY,the pH 10 and dosage 80?L/L for it The residual concentrations of Pb²⁺,Zn²⁺,Cd²⁺and Mn²⁺in the wastewater were 0.069 mg/L,0.88 mg/L,0.114 mg/L,2.22 mg/L,respectively.?2?The heavy metal ions in the high-salt wastewater of a lead and zinc smelter in Yunnan province can be removed under low pH?pH=10?by adopting a high-efficiency heavy metal chelating agents to strengthen lime neutralization and precipitation method.By comparing the experimental groups with heavy metal chelating agents and the blank groups with only lime,it was found that at the same pH,the removal effect of Pb²⁺,Zn²⁺,Cd²⁺and Mn²⁺in the experimental group with heavy metal chelating agents was better.?3?Considering the optimal dosage and pH of HDTC,XCBY obtained from single factor experiments,three-factor and three-level experiments were designed by response surface method,the optimal parameters for removal of metal ions in wastewater were determined through variance analysis and surface optimization as follows:pH was 10±0.2,the dosage of 6±0.2 mg/L for HDTC and 75.5±0.2?L/L for XCBY.The residual concentrations of Zn²⁺,Pb²⁺,Cd²⁺and Mn²⁺in the smelting wastewater were less than 0.15 mg/L,0.01 mg/L,0.05 mg/L,0.1 mg/L,respectively,the all results meet the specified limits in the Environmental Quality Standards?GB3838-2002?and basically realized the requirements of“zero emissions”.?4?In industrial test,the mixed use of HDTC and XCBY heavy metal chelate agent to strengthen the lime neutralization and precipitation method can remove a variety of heavy metal ions from the high-salt wastewater of a lead and zinc smelter in Yunnan province under a low pH?pH=10?condition and the concentration of Pb²⁺,Zn²⁺,Cd²⁺and Mn²⁺in the treated wastewater could decreased to 0.05 mg/L,0.15mg/L,0.05 mg/L and 0.1 mg/L respectively,it can ensure the stable operation of the subsequent membrane separation treatment system and low operating cost.And the original reaction process pH was 12-13,but pH 10 for the process after modification,the reduction of lime consumption was not less than 40%,and the production of decalcified slag?calcium carbonate?was not less than 40%.It is beneficial to?for?resource recovery of lime-calcium sulfate slag and reducing the cost of solid waste treatment,at the same time,on the premise of achieving zero discharge of wastewater,greatly reducing the cost of wastewater treatment operations.