Study On Treatment Of Electroless Plating Wastewater

The chemical plating process need to add a large number of complexing agent,which can make the metal attach to the material surface stably and form a stable and efficient electroless coating,but too much complexes can react with heavy metal ions to produce stable chelate.Traditional heavy metal ions removal method has been unable to effectively remove the heavy metal ions,so the wastewater containing heavy metals complex become the difficult problem of electroplating wastewater,therefore,it is urgent to explore technological process and optimum process parameters of such electroplating wastewater.In this paper the research of electroplating wastewater is taken from anqiu electroplating factory,the wastewater is comprehensive chemical plating wastewater containing copper and nickel ions.The comparison test of low concentration wastewater of 15mg/L copper ions and 256mg/L nickel ions in the factory showed that the removal rate of chelator precipitation method is low,which is not suitable for low concentration treatment of wastewater from this factory.After the metal copper nickel complex is broken by Fenton oxidation process,the concentration of copper and nickel ions in the wastewater is less than 0.5mg/L after adding alkali precipitation,and the treatment effect is better.As for the high concentration of electroless copper-nickel wastewater,the oxidation type ferrite method can reduce the concentration of 1250mg/L copper ions and 471mg/L ions in the wastewater to56mg/L and 82mg/L,and the treatment effect is better.The high concentration wastewater in this factory is pretreated by ferrite method,then Fenton oxidation method is used to break the complex,after that alkaline precipitation treatment is used to remove heavy metals copper and nickel ions from wastewater.The effects of wastewater precipitation pH,mass ratio of m^{[FeSO4·7H2O]}:m^[Ni2++Cu2+],the dosage of hydrogen peroxide,reaction temperature and stirring time on ferrite method were investigated.The conclusions were as follows:in the precipitation of p H is 10,the dosage of hydrogen peroxide is 27.75g/L,m^{[FeSO4·7H2O]}:m^[Ni2++Cu2+]is 18,the reaction temperature is 45?,the stirring time is30min,the average effluent concentration of copper ions was reduced from 1250mg/L to 55.74mg/L,the average concentration of nickel ions was reduced from 471mg/L to82.46mg/L,the removal rate of copper and nickel reached 95.54%,82.59%respectively.For low concentration wastewater,the effects of initial reaction pH,m^{[FeSO4·7H2O]}:m^[H2O2],hydrogen peroxide dosage,precipitation pH and reaction time on Fenton oxidation were studied.The main and secondary relationship of the influencing factors was determined by orthogonal experiment,and the optimum process conditions were determined by single factor experiment.The orthogonal experiment showed that the dosage of H₂O₂ was the biggest influence factors that affect the removal rate of copper and nickel ions,and secondary influence factors affecting copper ion removal rate was m^{[FeSO4·7H2O]}:m^[H2O2]and then the initial pH,the minimum factor was the precipitation reaction time and pH.For the influence of the removal rate of nickel ion,the precipitation pH was the second influencing factor,and then the the m^{[FeSO4·7H2O]}:m^[H2O2],initial pH and reaction time was the smallest influence factors.At the condition of the initial pH value of 3.5,the dosage of H₂O₂ is38.85 g/L,the mass ratio of ferrous sulfate and hydrogen peroxide is 1.2,the precipitation of pH is 10.5,the reaction time is 20 minutes,the copper and nickel ions removal rate reach 99.80%and 99.66%.The content of copper and nickel ions in the treated wastewater is 0.11 mg/L and 0.28mg/L respectively,which can meet the requirements of Table 2 emission in the emission standard of electroplating pollutants GB21900-2008.Through the two step treatment method of ferrite method and Fenton oxidation method,it is found that the treatment of 1m³ high concentration wastewater requires36.08 yuan for ferrite method,74.19 yuan for Fenton oxidation method and 110.27yuan for total reagent cost.