The Research Of Electroplating Wastewater Treated By Chemical Precipitation

Electroplating industry has become one of three most heavily-polluted industriesworldwide， because of producing masses of pollutants which are of complicatedcomponents and strong toxicity. At present, small electroplating enterprises with obsolescentproduction technologies and low level of pollution treatment abilities predominate inelectroplating industry in China, which greatly threatens human health and surroundingenvironment. It is very necessary to treat the domestic plating industry pollution by studyingthe properties of electroplating wastewater, exploring the practical, economic and effectiveelectroplating wastewater treatment technology as well as minimizing pollutants emissions.This paper briefly introduced the current situation of emission, properties and harms ofelectroplating wastewater and discussed the main method of electroplating wastewatertreatment. Taking some electroplating enterprise wastewater as research object, the propertiesof electroless nickel plating waste water and electroplating chromium plating waste waterwere analyzed. The practical and effective treatment methods of the two types of wastewaterwere discussed.In the experimental part, the effects of different complex-breaking agents on the removalrate of Ni2+in electroless nickel plating wastewater were discussed by adopting differentcomplex-breaking agents to treat Ni2+-containing wastewater and precipitating nickel ions.After using NaHSO3to reduce Cr6+to Cr3+, chemical precipitation process was adopted totreat Ni2+-containing. The optimum reaction conditions and the reasons of poor effects indifferent experimental conditions were discussed.The Experimental results showed the performances of different complex-breakingagents. The effect of H2O2was the poorest, almost no improvement. The effects of CaO andCaCl₂were very common, with corresponding removal efficiencies32%and19%. The effectof BaCl₂is the best, achieving a high nickel removal efficiency of more than99%. When thewastewater was treated by the joint treatment of CaO and BaCl₂, the result had theadvantages of good breaking complex performance and high Nickel removal ratio. Thedosage of BaCl₂needed in the joint process was much less than the only usage of BaCl₂toachieve the same Nickel removal performance.The results showed that, the deoxidization effect with NaHSO3on Cr6+fromCr-containing wastewater was very good. The efficiency of Cr6+being reduced to Cr3+is thehighest, closed to100%, when the pH was at2, and the dosage of NaHSO3was800mg/L. The precipitation effect was the best and the removal efficiency of total chromium could reach to99.5%, when pH was at8.Considering from the practical, economic and effective angle, it is reasonable to usedifferent methods to improve the effect of Chemical precipitation, and optimize chemicalprecipitation processing on the treatment of wastewater from electroplating chromium andelectroless nickel plating, combining the actual situation of the treatment of electroplatingwastewater at present in our country, The research results could be practically applied towastewater treatment processes, be helpful to reduce emission of pollutants fromelectroplating wastewater, and reduce the adverse impact on ecological environment.