Effect of different pore membrane on ultrafiltration treatment of wastewater contained heavy metals complexed by palygorskite

Abstract

The treating effects of four hollow fiber membranes on heavy metals complexed by palygorskite in wastewater by complexation–ultrafiltration were investigated. The membranes contained three asymmetric polysulfone membranes and a polyethersulfone membrane with nominal molecular weight cut-off (MWCO) between 6,000 and 100,000 Da. The results through the comprehensive analysis of the rejection rate and the flux of normalized membranes showed that 6,000; 10,000 and 6,000 Da ultrafiltration membranes were suitable for the ultrafiltration of Cu2+, Zn2+, Cd2+, respectively. The pseudo-first-order reaction rate equation can better represent the reaction behavior of the complexes of favorite-ultraviolet at four membrane pore sizes. Four kinds of ultrafiltration membranes with molecular weight cut-offs of 6, 10, 50, and 100 kDa were fouled with wastewater containing Cu2+, Zn2+, Cd2+ complexed by palygorskite in complexation–ultrafiltration process at a transmembrane pressure of 1 bar and 20°C. The influence of molecular weight cutoff was investigated. The permeation flux decreased with time. Permeate flux declined with time gradually and finally stabilized after about 140 min of operation for all the membranes tested. 50,000 Da membrane showed the highest flux decline. The concentration of heavy metals and types of materials affect the distribution of resistance. The highest proportion of resistance for 6,000 and 10,000 Da membranes is the resistance of the membrane. For 50,000 and 100,000 Da membranes, the highest proportion of its resistance is the filter cake layer resistance. The results provide a kind of inorganic clay complexing agent in large reserves for the complexation–ultrafiltration of heavy metal wastewater.