The Study Of Treatment Experiment Of Electroless Nickel Plating Wastewater

Electroless nickel plating wastewater, have lots of nickel ions, sodium phosphite, sodiumhypophosphite, the pH buffer and stabilizer of organic matter. The nickel is not only acarcinogen, but also a shortage of expensive heavy metal resource. As we all know thatphosphorus is a major pollution factor, which result in water eutrophication phenomena,because of there are large amount of reducing agent and stabilizer in the electroless nickelwastewater have high concentration of COD_Cr, therefore, electroless nickel plating wastewatertreatment is quite complex. How to deal with the electroless nickel plating wastewatereffectively and reduce environmental pollution and ecological destruction, which have greatsignificance.In the paper, electroless nickel plating wastewater as the research object, mainly adoptschemical precipitation method, Fenton oxidation and chemical coagulation method to dealwith nickel, phosphorus and COD_Cr.Chemical precipitation method to deal with the wastewater of nickel, using Na2S as theprecipitating agent, through Na2S dosage, reaction time, temperature and pH of four factorson the removal rate of nickel in liquid waste. Studies have shown that: the pH was6, and thetemperature was15℃, adding30ml sodium sulfide solution（250g/L）, one hour after thereaction, the removal rate of nickel reached99.99%, with the residual concentration of thenickel was0.53mg/L, reached the National Emission Standards and recovered nickel metal inthe wastewater.With CaO as the precipitating agent, removal of hypophosphite, phosphite and TP in theelectroless nickel plating wastewater. Investigated the effects of removal above of the three byCaO dosage, pH, reaction temperature and reaction time. Studies have shown that: the pH ofthe solution was6, temperature was60°C, and dose of CaO was10g, after reaction for2h, theremoval rate of the three, respectively:99.40%,99.67%and99.98%, and remaining TP in thewastewater was less than1.5mg/L, and reached the National Emission Standards. Fenton oxidation to reduce the COD_Crin the electroless nickel plating wastewater,research has shown that the optimum conditions of Fenton oxidation as follows: the pH was4,adding60g/L FeSO4·7H2O and30ml/L of H2O2, under the condition of the30°C, reacting for45min, the removal efficiency of the COD_Crreached94.19%.After Fenton oxidation wastewater futher by coagulation and sedimentation treatment,results have shown the best condition of coagulation and sedimentation was pH=10,30°C.The total removal of the COD_Crwas99.16%, and the remaining residue in wastewater was841mg/L.