Research Of Removal Copper And Nickel Of Electroplating Wastewater By Flocculation Precipitation And Micro-Filtration Combined Process

Copper and nickel plating are the two plating species which are widely applied in the electroplating, the wastewater containing copper and nickel are accounted for about 40% of electroplating wastewater, and under some certain conditions they have direct or potential hazards to environment. So the copper and nickel contamination and treatment can not be ignored. They are usually classified as"general heavy metal wastewater"to be treated together, which cause a lot of problems such as low efficiency, a large amount of sludge, producing secondary pollution and the higher integrated cost and so on. The flocculation-microfiltration (be short for flocculation-MF) combined process is recommended to treat electroplating wastewater, and most kinds of factors which affect the efficiency of the process are studied.The optimum conditions of FeSO₄ and PAC (Aluminium Polychlorid) flocculation are following, under the inside temperature, when the dosage are respectively 15, 12.5mg/L and 12.5, 7.5mg/L, the removal rate of Cu²⁺,Ni²⁺ respectively reach the maximum 99.60%, 93.13% and 98.80%, 92.02%; the optimum pH value are respectively 8.5, 9.6 and 8.5, 9.5; the stirring condition are rapid stirring 400rpm with 30s, medium-speed stirring 100rpm with 10min, slow stirring 50rpm with 15min and rapid stirring 500rpm with 30s, medium-speed stirring 150rpm with 5min, slow stirring 90rpm with 10min; the initial concentration have little influence on FeSO₄ and PAC flocculation efficiency, the concentration of flocculants should be accordingly improved when the initial concentration of wastewater are increasing; the precipitation time is about 30⁴0min.In the course of microfiltration, the wastewater initial flux is 12L/m²Â·h when the pressure is 0.1MPa and aeration volume is 0.5m³/h under the inside temperature. The experimental results indicate that the filtration efficiency is better when the MLSS is 0.5～1.0g/L, and the flux can be maintained about 11L/m²Â·h after membrane module running stably and orderly. The membrane rejection rates are not affected by initial concentration of wastewater within 100mg/L. Furthermore, it is helpful to employ FeSO₄ flocculation as pretreatment that can not only improve membrane rejection rate but also delay the membrane fouling, and FeSO₄ flocculation-MF process cause less membrane fouling than PAC flocculation-MF, and the fouling can be clean up easily. The experiments show the mixed cleaning method of physical and chemical is more effective than the single cleaning method.FeSO₄ flocculation-MF process can operate stably in the course of treatment through the test treatments of electroplating wastewater from Changzhou Xilin electroplating Ltd., and the pH value of effluent is about 8.0～8.5, the concentration of Cu, Ni in effluent are average 0.152, 0.875mg/L, the removal rate of metal ions of Zn, Fe, Al and the trace metals such Cd, Mn can arrive at the national-level discharge standard, and meantime, the removal rate of COD and colority average 43.04% and 48.96%.