| A novel coupling technology of water-soluble polymer complexation-ultrafiltration has been studied,in which water-soluble polymer was reacted with metal ions to form metal complexes and PVDF ultrafiltration membrane was used to concentrate the complexes. Two kinds of industrial heavy metal wastewater including heavy metal Sn and Zn were introduced.The coupling process has been investigated systematically,incl-uding rejection coefficient of complexation systems,selective separation of metal ions,and decomplexation of complexes.The process operational parameters and comple-xation behavior were also concerned.At last,it has been discussed to apply the technology to the treatment of wastewater containing tin ions discharged from a electroplating tin board factory.Firstly, the high efficiency complexants, polyacrylic acid sodium salt (PAASS) and polyethyleneimine (PEI), were selected on the basis of complexation-ultrafiltration cou-pling process and the characteristics of complexants and metals. Then the precondition-ing was studied to keep R=100%. The method of determing metal concentration in wastewater and water samples by Air-C2H2 flame atom absorption spectrometry was established.Secondly, Two kinds of industrial heavy metal wastewater including heavy metal Sn and Zn were studied respectively,on the basis of the mechanism of the complexation-ultrafiltration coupling process, the various factors such as pH, complexation concentration,loading ratio (L), ion strength,volume concentration factor (VCF), pressure operating time and velocity across the membrane for industrial heavy metal wastewater were investigated at the laboratory in order to confirm optimal technics conditions. The results showed that the retention of Sn metal achieved 95.23% with the reducing of L, that was the critical loading ratio. Therefore, various K values were as follows:when pH=4.0,KSn=0.055mgSn2+/mgPAASS;pH=6.0,KSn=0.030 mgSn2+/mgPEI.Then keeping increasing L, R began to decline linearly. Meanwhile the retention of Zn metal achieved 100% with the reducing of L, that was the critical loading ratio. at the condition of pH=7.0, the complexation capacities of PAASS and PEI to heavy metal Zn ion:KZn=0.10mgZn2+/mgPAASS, KZn=0.050mgZn2+/mgPEI.Thirdly, the separation properties of two kinds of binary solution were investigated. By the comparison of single metal ion with mixture metal ions rejection coefficients, effects of operational parameters on selective separation were studied.It could be seen that pH value and loading ratio L played an important role in the prosess of selective separation. When binary rare earth solution was complexed with PAASS, retention of Sn2+ was not affected by the existence of Zn2+. Zn2+ and Sn2+ have the near complexation capacities of PAASS, so they can not be separated by this process. But when they complex with PEI, the selective separation coefficient S increased as the pH value increased. At pH=7.0 and L=0.10, the selective separation coefficient S was reached 126. This leads to the selective separation of Zn2+ and Sn2+.Fourthly, the metal separation and the polymer recovery from the concentrated wastewater by complexation-ultrafiltration coupling process were studied with continuous dia-ultrafiltration and membrane fouling and cleaning were also investigated. It was found that when the washing water volume was four times than initial solutions, the washing removal ratio of Sn2+and Zn2+could be reached respectively 95.80% and 94.60%. The efficiency of the recovered Polymer is same as the fresh PAASS in the processes.As for membrane cleaning, it was available to recover the properties of the membrane by the treatment of acid and alkali solutions.Finally, the coupling process of complexation-ultrafiltration was applied to treat the low concentration wastewater containing tin discharged from a electroplating tin board factory.Under the conditions of pH=4.0 and L=0.045, it was found that permeate flux declined slowly, and Sn2+ and organic concentrations in the permeate were lower than the requirements by the national standard for wastewater discharge,and the permeate could be up to the standard of wastewater reuse. Sn2+ could be concentrated from 12.70 to 1240.50 mg/L.In the coupling process,tin complex could be decompounded perfectly,and polymer be reused effectively and membrane fouling be removed easily.Therefore,the novel coupling process would open up a range of application possibilities meeting the requirements in the treatment of industry heavy metal wastewaters.
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