Mechanisms of lead biosorption on cellulose/chitin beads

Abstract

Environment-friendly cellulose/chitin beads being prepared by coagulating a blend of cellulose and chitin in 6 wt% NaOH/5 wt% thiourea aqueous solution with 5% H 2SO 4 possessed higher heavy metals uptake capacity than pure chitin flakes. The mechanisms of Pb 2+ adsorption on cellulose/chitin beads at pH 0=5 were investigated at the molecular levels by scanning electron micrographs (SEM), transmission electron micrographs (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (XRD). The result revealed that mechanisms for the adsorption of Pb 2+ on the cellulose/chitin beads could be described as complexation between Pb 2+ and N atom in the chitin, and further adsorption of Pb 2+ nearby the complexed Pb 2+ and precipitation of the hydrolysis product of the Pb 2+ complex on the beads as the crystalline state. Furthermore, structural factors such as larger surface area of the beads resulted from microporous-network structure, low crystallinity of cellulose/chitin beads and high hydrophilicity induced by hydrophilic skeleton of cellulose played an important role in increasing adsorption ability.