Study On Removing Heavy Metals From Electroplating Sludge Based On Electrokinetic Remediation Technology

With the development of social economy,the environmental pollution is getting worse,specifically by electroplating industry which contains large amount of strong acid and heavy metals.Excessive alkali neutralization and flocculation processes generate sludge with rich Cu、Zn、Ni、Cr、Cd,etc.Without proper treatment,the accumulation of sludge will not only occupy land resources,but also produce secondary pollution.In this paper,we studied the heavy metals removal by a self-designed electrokinetic remediation device in a electroplating sludge from Linping,Hangzhou.Further,we studied the enhancement effect of citric acid on heavy metals removal by lectrokinetic remediation technology.The results indicated that at a current of 0.7A,for the removal of Zn and Ni reached highest at 20.2%and 24.8%respectively.The Cu removal reached 15.8%at electric current of 0.8A,while the Cr removal was 11.3%at a current of 0.9A.However,the cationic membrane loss increased with along with the electric current,therefore,0.6A was chosen as the optimal current.Cationic membrane replacement experiments indicated that the removal rate of Ni,Zn,Cu,and Cr were up to 70.9%,69.5%,53.2%,and 69.5%respectively when replacing membrane every two days,when the Cationic membrane loss was minimum too.The morphology distribution of heavy metals were effectively changed after adding citric acid,the heavy metals became unstable.The removal rate of Cu and Cr increased up to 55.8%and 61.1%when the proportion of adding citric acid was 80g/kg and 120g/kg respectively.For Zn and Ni in the sluge,the removal rate was only increased by 3.7%and 4%compared with no citric acid added,although the morphology distribution of heavy metals had changed a lot by the pretreatment of adding citric acid.