Identification And Disintegration Of Anionic Nickel Complexes In Electroplating Wastewater

In recent years,treatment of high content nickel plating wastewater containing single complexing agent has been extensively studied,whereas few reports on wastewater containing high content of a variety of nickel complexes are available.In the current study,surfactants and ion resin were used to identify anionic metal complexes in synthetic nickel-containing wastewater?complexing agent: citric acid and EDTA?,which is useful for selection of appropriate removal technology.Fenton,UV/H₂O₂ and UV/Fenton were selected to decompose Ni complexes,by examining effects of sedimentary pH,n?H₂O₂?:n?Fe2+?,H₂O₂ dosage,initial pH and reaction time on the removal rate of Ni2+.The results would be provide some references for real nickel plating wastewater treatment.Surfactants and ion resin can successfully identify anionic metal complexes in Ni-containing wastewater.The results show that the anionic metal complexes can be rapidly and simply identified by the two methods.Under the conditions,the nickel-citric acid,the EDTA-nickel and the citric-EDTA-nickel were assigned to anionic metal complexes.These results were further verified by metal speciation simulation by MEDUSA software.For the nickel-citric acid wastewater,it can be effectively treated by Fenton and UV/Fenton process,but not UV/H₂O₂.The results show that the optimal conditions for Fenton oxidation process were as follows: initial p H = 3.0,H₂O₂ dosage = 1.5 mmol/L,n?H₂O₂?: n?Fe2+?= 1.5:1,reaction time = 1 h,sedimentary pH = 11.0.Under the conditions,the removal rate of Ni2+ could reach 98%.The remaining content of nickel was 0.10 mg/L.The results show that the optimal conditions for UV/Fenton oxidation process were as follows: initial pH = 3.0,H₂O₂ dosage = 0.9mmol/L,n?H₂O₂?: n?Fe2+?= 1.5:1,reaction time = 1 h,sedimentary pH = 11.0.Under the conditions,the removal rate of Ni2+ could reach 98%.For the EDTA-nickel wastewater,it can be effectively treated by UV/Fenton process,but not UV/H₂O₂ and Fenton.The results show that the optimal conditions for UV/Fenton oxidation process were as follows: initial pH = 3.0,H₂O₂ dosage = 2 mmol/L,n?H₂O₂?: n?Fe2+?= 2:1,reaction time = 1 h,sedimentary pH = 11.0.Under the conditions,the removal rate of Ni2+ could reach 98%.For the citric-EDTA-nickel wastewater,it can be effectively treated by UV/Fenton process,but not UV/H₂O₂ and Fenton.The results show that the optimal conditions for UV/Fenton oxidation process were as follows: initial pH = 2.6,H₂O₂ dosage = 3 mmol/L,n?H₂O₂?: n?Fe2+?=3:1,reaction time = 1 h,sedimentary pH = 11.0.Under the conditions,the removal rate of Ni2+could reach 98.3%.