Polyamide/PVC based composite hollow fiber nanofiltration membranes: Effect of substrate on properties and performance

Thin film composite nanofiltration membranes were successfully prepared via interfacial polymerization between piperazine and trimesoyl chloride on poly(vinyl chloride) hollow fiber substrates with different properties. Both the polyamide layer and underlying substrate were characterized with respect to chemical and morphological structures. The effects of substrate properties on the characteristics of the prepared nanofiltration membranes were investigated. It is found from the results that the differences in substrate properties, mainly the membrane pore size and porosity had significant contributions to the changes in the thickness and cross-linking degree of poly(piperazine-amide) layer during the interfacial polymerization process, leading to the varied performance of the prepared nanofiltration membranes in terms of MgSO4 rejection and permeate flux. The nanofiltration membrane prepared from the substrate with medium pore size and porosity exhibited a relatively higher permeate flux as well as a superior rejection for MgSO4, which showed typical rejection orders for different salts as well as good stabilities after backwash treatment and a long-term filtration process. These results indicate that the prepared poly(vinyl chloride) nanofiltration hollow fiber membranes could be applied to the desalination or water softening process.