Research On The Removal Of Nickel-complex From Electroplating Wastewater

The composition of electroplating wastewater was complicated. It contained a variety of heavy metals which was harmful to human and environment, especially the nickel. The complexes can complex with nickel ions, so it will increase the difficulty of wastewater treatment. In this research, some methods, such as Fenton and UV/H2O2, were used to deal with the nickel-containing wastewater which complexed with single complexing agent(tartaric acid, citric acid, EDTA and ammonia). The results can provide the basic for the treatment of actual wastewater.The paper showed results by experiments and theoretical calculation, when tartaric acid, citric acid, EDTA and ammonia were presenced in the water, the total nickel can not meet the discharge standard by chemical precipitation. To meet the total nickel level in the emission standard of pollutants for electroplating (GB21900-2008), the concentration of tartaric acid, citric acid, EDTA and ammonia should be reduced.For the nickel-tartaric acid wastewater, using Fenton and UV/H2O2 process can achieve good results. The optimized experimental conditions for Fenton oxidation process were initial pH= 3.0, the dosage of 30% H2O2 solution=1.33 mL/L, n(Fe2+):n(H2O2)= 1.4:1,1 hour of reaction time, precipitation pH= 10.0, and the nickel can reduce to 0.1 mg/L after treatment. The optimized experimental conditions for UV/H2O2 process were initial pH= 3.0, the dosage of 30% H2O2 solution= 2 mL/L,120 minutes of reaction time at 15 W UV lamp irradiation and precipitation pH=10.0, and the nickel can reduce to 0.36 mg/L after treatment.For the nickel-citric acid wastewater, using Fenton process can achieve good results, while using UV/H2O2 process just get poor results. The optimized experimental conditions for Fenton oxidation process were initial pH= 3.0, the dosage of 30%H2O2 solution= 1.33 mL/L, n(Fe2+):n(H2O2)= 1.4:1,1 hour of reaction time and precipitation pH= 10.0, and the nickel can reduce to 0.46 mg/L after treatment.For the EDTA-nickel wastewater, using anion exchange resin to adsorb nickel in wastewater can achieve good results, while using Fenton, UV/H2O2 process just get poor results. The total nickel can be removed by RX-21, RX-31 resin at the condition of flow rate= 4 BV/h, volume of wastewater below 40 BV.For the nickel-ammonia wastewater, using chelating resin, MAP (magnesium ammonium phosphate) process can achieve good results. The optimized experimental conditions for MAP process were n(PO43-):n(NH3):n(Mg2+)=1.2:1:1,precipitation pH=10.0 and 2 hours reaction time,and the nickel can reduce to 0.1 mg/L after treatment.