Preparation of green chelating fibers and adsorption properties for Cd(II) in aqueous solution

Abstract

Chitosan chains (CTS) were grafted onto polyvinyl alcohol fibers (PVAf) with the aid of coupling agent γ-glycidoxypropyltrimethoxysilane, producing grafted fibers PVAf-g-CTS. Then, chloroacetic acid (CA) was used to react with the chitosan chains on the PVAf-g-CTS surface via nucleophilic substitution reaction to produce fibrous PVAf-g-CACTS with multiple adsorption sites. The products were characterized by using FTIR, SEM, XRD and XPS, revealing that the reaction followed the S N 2 mechanism. Optimum parameters, including a reaction temperature of 50 °C and a mass ratio of PVAf-g-CTS to CA of 1:0.12, were determined for the reaction. Adsorption experiments confirmed that PVAf-g-CACTS showed greater adsorption characteristics for Cd(II) in aqueous solutions compared with PVAf-g-CTS and PVAf. In particular, the rate of Cd(II) uptake by using PVAf-g-CACTS was higher, and the equilibrium was reached within 80 min. When pH was 7, the saturated adsorption capacity reached 47.65 mg g−1. The adsorption kinetics conformed to the pseudo-second-order model, and the adsorption process was in accordance with the Langmuir and Temkin isotherm model. Adsorption–desorption cycle experiments showed that PVAf-g-CACTS had good performance of reuse, and the adsorption mechanism was analyzed further by using XPS.