Functionalized nonwoven Nylon fabrics for cadmium ion exchange applications

摘要

Water pollution is a big issue of our world. This research aims to study the possibility of using carboxylate functionalized synthetic nonwoven fabrics for removing heavy metals from contaminated water. Poly(acrylic acid) (PAA) and poly(itaconic acid) (PIA) were grafted from the surfaces of individual Nylon 6,6 fibers of nonwoven fabrics by radiation induced-polymerization with Gamma-rays under various conditions. FTIR spectra show evidence of the carboxylate groups of PAA and PIA after polymer grafting. A comparison of fiber sizes and surface morphology of nonwoven Nylon fabrics before and after PAA and PIA grafting was examined using optical microscopy (OM) and scanning electron microscopy (SEM). The shrinkage, curl and non-uniformity of fibers observed by OM and SEM after polymer grafting might cause the changes in the water permeabilities of the modified Nylon fabrics. After hydrolyzation of modified Nylon fabrics with sodium hydroxide, static cadmium (Cd2+) ion exchange capacities were measured for all fabric samples. The Langmuir model was used to calculate parameters, including maximum static Cd2+ ion exchange capacities and the association coefficients to explain behaviors of unmodified and modified nonwoven Nylon fabrics. Using unmodified and PAA- and PIA- modified Nylon fabrics as ion-exchange membranes, these membranes provide higher water flowability than conventional membranes. Furthermore, the static Cd2+ ion exchange capacities of these ion-exchange membranes are comparable to commercial ion-exchange materials. It was also found that duration time of radiation inducing and heating steps along with various types of polymer grafting affected the ion exchange capacities and membrane performance.