Polyphenylsulfone membrane blended with polyaniline for nanofiltration promising for removing heavy metals (Cd2+/Pb2+) from wastewater

Abstract

This study reported polyaniline (PANi), an emerging multifunctional nanomaterial, for fabricating the polyphenylsulfone (PPSF)–PANi nanocomposite membrane for nanofiltration (NF) to remove heavy metals (Cd2+/Pb2+) from wastewater. PANi was synthesized via oxidative polymerization of an aniline monomer at a low concentration (≤0.1 M). Furthermore, the nanostructure of PANi was determined using transmission electron microscopy. The membrane structure and characteristic properties were studied in terms of surface and cross-section morphologies, topography, hydrophilicity, and surface charge using scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle (CA) measurement, and zeta potential measurement, respectively. Thermal and mechanical properties and casting solution viscosity were also studied. The SEM results demonstrated that PANi inclusion helped to construct a typical asymmetric membrane with a pore size of ∼1 nm. Additionally, it enhanced the surface properties, which was indicated by a more considerable hydrophilicity (CA ≤ 52) and a shift in the zeta potential from −40 to −10 mV. Increasing the PANi concentration from 0.25 to 0.50 wt% aided the heavy metal rejection by the nanocomposite membrane, affording an increase of the Cd2+/Pb2+ rejection. However, the Cd2+/Pb2+ rejection decreased when the PANi concentration was 1.0 wt%. The optimized PPSF–PANi nanocomposite membrane at 0.50-wt% PANi exhibited a water permeability of 1.8 LMH/bar and high rejections of 99% and 95% toward Pb2+ and Cd2+, respectively. Tensile strength and TGA tests also revealed the role of PANi as a positive reinforcement on the mechanical and thermal properties of the membrane.