Exploring a novel family of poly(amide-imide)s as promising cationic sorbents for water remediation

Abstract

A new monomer 5-(5-(chlorocarbonyl)-1,3-dioxoisoindolin-2-yl) isophthaloyl chloride was synthesized and subsequently condensed with a variety of diamines yielding a novel family of poly(amide-imide)s (PAIs), which were exploited as potential cationic sorbents for water treatment. The synthesized monomer and all PAIs were characterized using Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopic analyses. High thermal stability and molar masses of the whole PAIs family were determined using thermogravimetric analysis (TGA) and gel permeation chromatography (GPC). Decomposition temperatures and char yields were found to be in the range 422-600 °C and 2–57% respectively. X-ray diffraction (XRD) patterns revealed the crystalline nature of PAIs family with few exceptions. PAI-2 was found to be the best contender with 99% optimum adsorption capacity for both Cd(II) and Pb(II) cations at optimal conditions. Adsorption capacities have been improved till 700 and 800 mg/g for Cd and Pb respectively for 100 ppm feed concentration, which depicted the efficiency of adsorbent. Adsorption data of all PAIs fitted well to Langmuir as compared to Freundlich, Temkin and Dubinin-Radushkevich adsorption models and exhibited favorable monolayer adsorption mechanism. The relative uptake of cations by PAIs followed the preferential trend Fe(II) > Pb(II) > Cd(II) > Cu(II) in a mixture of metal ions.