Pollutant Removal Treatment Of Electroplating Wastewater

Electroplating is an indispensable link in today’s industrial chain,and it is also one of the three major pollution industries in the world.The electroplating process is complicated,including pre-plating pretreatment,electroplating and plating process.Those three processes will produce electroplating wastewater of different properties with complex composition.And the rise of and electroless nickel plating process and zinc-nickel alloy plating process has also increased the difficulty of wastewater treatment.Electroplating Wastewater Discharge Standard（GB21900-2008）puts more stringent emission standards on ammonia nitrogen,heavy metals,COD and other indicators in the electroplating industry wastewater,making the actual treatment of electroplating wastewater more difficult,and the wastewater treatment problem has been become a bottleneck restricting factor for the survival and development of electroplating enterprises.Therefore,research on the actual electroplating wastewater treatment process is imperative.In this paper,several different wastewaters produced by electroplating pretreatment and electroplating in JiangXi Electroplating Park were studied,and the removal of ammonia nitrogen,COD and nickel were investigated and optimized.Physical and chemical methods were used to treat the high concentration ammonia nitrogen.To approach an optimal removal of ammonia nitrogen by the method of response surface.The results showed that the optimum conditions for air stripping process were as follows:When pH was at 11,aeration rate was at 2 min/L,reaction time was at 60min,the removal rate of ammonia nitrogen reached 98%.Afterwards,the stripped wastewater was also oxidized by NaClO.It showed that 95.43%of ammonia nitrogen was removed,when the NaClO dosage was 30 mL/L and the reaction time was 10 min.The effects of ultrasound and UV irradiation on the oxidation efficiency of NaClO were estimated.The content of effluent ammonia nitrogen after treatment by the given process meets the table 3 of the national discharge standard（GB 21900—2008）.The MAP method was used to treat low concentration NH₃-N After primary treatment.When the reaction time was 20 min,the molar ratio of MgCl₂:MgO was 1:4,and the molar ratio of N:Mg was 1:1.6,the removal rate of NH₃-N could reach over 96%.From 180mg/L to below 8mg/L.The Fenton method was used to carry out COD degradation experiments on electroplating wastewater,and the influence of key influencing factors on the removal efficiency of Fenton oxidative degradation of COD was systematically studied.The results showed that at pH=3,the dosage of H₂O₂ was 0.96ml/L,and the molar ratio of Fe²⁺/H₂O₂was 1:5.Under this condition,the COD removal rate reached 65.8%.Ultraviolet radiation helps increase COD removal efficiency by approximately 26.8%.After Fenton treatment,ammonia nitrogen and Cu²⁺in the wastewater also achieved different degrees of removal rate.Removal of nickel from several different concentrations of electroplating nickel wastewater by hydroxide coagulation precipitation method,Results of the experimental are as follows:For electroplated nickel wastewater with a nickel concentration of6617 mg/L,Preliminary breakdown by sodium hypochlorite was researched the effect of NaOH and Ca（OH）₂ on the coagulation and precipitation of Ni²⁺was compared.The effect of calcium hydroxide on the removal of Ni²⁺was better than that of sodium hydroxide.Since the amount of sludge produced by adjusting the pH with calcium hydroxide is particularly large,secondary pollution is generated in the same time,which increases the cost for the enterprise.The pH of the wastewater is adjusted to 12 by sodium hydroxide,and flocculation and precipitation can be the better choice.For 214.3mg/L and 64.6mg/L of the nickel wastewater,the choice of sodium hydroxide coagulation precipitation method has the best effect on nickel removal at pH=12,and the addition of 50mg/L polyferric sulfate helps nickel reach a better removal rate,Which is above 98%.The treatment methods of high ammonia nitrogen,heavy metal nickel and COD wastewater studied in this paper are applied to the treatment of actual wastewater in an electroplating centralized control park in Jiangxi Province.The discharged electroplating wastewater discharge indicators have all reached the Electroplating Pollutant Emission Standard（GB21900）.-2008)Table 3 emission requirements.