| Electroplating wastewater,with many kinds of toxic and hazardous substance,have attracted much attention in the industrial wastewater treatment field.However,it is difficult to deal with the electroplating wastewater for its characteristic of large volume while low concentration of heavy metal and the treatment cost is always high.Electroplating wastewater can cause a wide range and persistent pollution.The heavy metal in the wastewater can eventually reach the top of the food chain,the human,via bio-accumulation and thus do serious harm to human body for chronic poisoning.Many methods have been developed to treat electroplating wastewater such as chemical method,evaporating-concentration method,biologic method,adsorption,ion exchange, membrane-separation technique and so on.All of them have advantages as well as the disadvantages.The chemical method produce a large amount of sludge and its purified water can not be reused for its high salinity.Evaporating-concentration method requires high energy consumption.And the adsorption is limited by the adsorption rate,capacity and regeneration of the adsorbent.As for the ion exchange,it needs the regeneration of large quantity of acid and alkali solution,which makes it hard to manipulate and cost high.Moreover,the process may cause secondary pollution problems.The membrane-separation technique is not effective to treat the low concentration electroplating wastewater.Eletrodialysis is easy to involve in concentration polarization and high energy consumption.All those technologies can not meet the demand of qualified effluent,recycling of heavy metal as well as low cost.The thesis systematically studied the removal and recycling of ions from electroplating wastewater by electrodeionization.And the research mainly focused on the removal of Cu2+, Zn2+,Cl-,SO42-,several kinds of cations and anions in the electroplating wastewater,heavy metal cations chelated by pyrophosphate.The research results show that the EDI technology is an effective method.①When Cu2+ concentration was 50mg/L,and the applied voltage was 30V,the enrichment factor is 10.9;removal efficiency is 98.3%～99%.And Cu2+ was hardly detected in the purified water.As for the Zn2+,the enrichment factor is 10.29 and the Zn2+ concentration in purified water was 0.875～1.721 mg/L while the conductivity was 43.5～69.6μs/cm. ②The removal of mixed cations was investigated.Afer 15.5 hours,the removal rates were more than 99.9%.This indicates that several kinds of heavy metal cations can be stimultaneously deeply removed.③At the 30V applied voltage,the enrichment factor for Cl-was 14.07,80%～88%removal efficiency.The conductivity in purified water was 43.5～69.6μs/cm.The concentration of SO42- in purified water was 2.34～2.75mg/L.These results demonstrate that the wastewater containing Cl-can be purified by EDI.④The removal of mixed anions has also been studied.After 7 hours work,the removal efficiency is 94.52%～98.6%.Several kinds of anions can be stimultaneously deeply removed.⑤The removal of[Cu(P2O7)2]6-,[Zn(P2O7)2]6- was investigated.Ater 12 hous,the coper removal efficiency is 96.88%and zinc 88.23%.⑥Recovery of metal ions from real electroplating rinsing water for purification.The results shows that after 14 hours operation,the concentration of copper is 611.2mg/L,enrich factor is 16.72,the concentration of nickel is 517.99mg/L,enrich factor is 22.23;the concentration of zinc is 13.53mg/L,enrich factor is 38.9.And the removal effiency is 99.9%.
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