化学沉淀-微滤-络合-超滤处理高浓度含镍废水

在pH=9下,镍离子浓度为5562.71mg/L的镍废水经充分沉淀后,以0.5μm孔径陶瓷膜微滤处理,发现浓缩时膜通量(J)先快速降低,经缓慢下降后,再较快降低,镍截留系数(R_Ni)接近1,当体积浓缩因子(VCF)从1增大到10时,截留液镍浓度(C_r)从5562.71mg/L浓缩至55507.76mg/L,渗透液镍浓度(C_p)为13.26mg/L.以陶瓷膜渗透液为料液,以聚乙烯亚胺为络合剂,考察聚合物与金属质量比(r_p/m)、pH值、温度和操作压力对恒容超滤R_Ni和J的影响,并研究超滤浓缩过程.结果表明,R_Ni随r_p/m或pH增大而增大,随温度升高而略下降,与操作压力无关;J随温度或操作压力增大而增大,随pH增大而增大至不变,r_p/m对J影响甚微.超滤浓缩时,控制r_p/m=7和pH=9,当VCF从1增大到30时,J仅下降9.76%,C_r从13.26mg/L增大至396.64mg/L,C_p约0.04mg/L,镍离子被浓缩,超滤渗透液可直接排放.

Treatment of wastewater containing high concentration nickel ions with precipitation-microfiltration-complexation-ultrafiltration processes

The wastewater containing high concentration(5562.71mg/L) of nickel ion was first completely precipitated at pH 9, and subsequently treated by a ceramic microfiltration membrane with a pore diameter of 0.5μm. During the concentration process, the membrane flux(J) dropped significantly at the initial stage, then declined slowly, and finally decreased at a rapid rate again. The nickel rejection coefficient(R_Ni) was found to be approx. 1. When the volume concentration factor(VCF) increased from 1to 10, the nickel concentration in the retentate(C_r) increased from 5562.71 to 55507.76mg/L, whereas the nickel concentration in the permeate(C_p) remained nearly constant at approx. 13.26mg/L. Then, the complexation-ultrafiltration process was studied using the permeation fluid from the microfiltration process as the feed solution. Poly(ethylene imine) was employed as the complexing agent. The effects of the polymer/metal mass ratio(r_p/m), pH, temperature and operating pressure on R_Ni and J were investigated. Further, the process of ultrafiltration concentration was studied. The results showed that R_Ni increased with increasing r_p/m or pH and decreased slightly with temperature, and that the operating pressure exerted no effect on R_Ni; J increased with temperature or operating pressure. With increasing pH, J increased at first, and then reached a constant value. The effect of r_p/m on J was insignificant. The ultrafiltration concentration experiment was carried out at r_p/m=7 and pH=9. When VCF increased from 1to 30, J only declined by 9.76%. C_r increased linearly from 13.26to 396.64mg/L, whereas C_p remained roughly unchanged at about 0.04mg/L. Nickel ions were concentrated effectively, and the permeation solution from the ultrafiltration process was discharged directly.