Preparation and performance analysis of chitosan/polyacrylamide/poly (vinyl alcohol)/Fe/glutaraldehyde copolymer for Cr(Ⅵ) adsorption

摘要

In this study, chitosan/polyacrylamide/poly(vinyl alcohol)/Fe/glutaraldehyde (CPPFG) copolymers, termed as CPPFG I, II, III and IV, respectively, were prepared with corresponding amounts of glutaraldehyde (GA). These copolymers were then employed to do batch experiments as a function of pH, Cr(VI) initial concentration, contact time, temperature and coexisting anions to study Cr(VI) adsorption process. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to explore the characteristics of the adsorbents before and after loaded Cr(VI) and adsorption mechanism. The results showed that the copolymers had a fast adsorption rate and high adsorption efficiency above 99.50% which was hardly affected by initial pH values varying from 3.0 to 8.0 and the anions. The adsorption fitted Langmuir and Temkin isotherm models well. The removal of Cr(VI) followed pseudo-second-order and intrapartide diffusion kinetic models, and its rate was mainly controlled by chemical adsorption and intrapartide mass transport. The calculated thermodynamic parameters (Delta G(0), Delta H-0 and Delta S-0) demonstrated that the adsorption was a spontaneous and endothermic process. The adsorption capacity and rate were strongly depended on the quantity of the available functional binding sites (i.e., -OH, -C=N and -NH), and surface morphologies with different GA cross-link densities under the studied conditions. The possible mechanism was proposed based on the data of FTIR, XPS, SEM and zeta potential. Adsorption properties comparison showed the copolymer was an alternative as adsorbent to remove Cr(VI) from natural water.