Novel application of xanthan gum-based biopolymer for heavy metal immobilization in soil

Abstract

The sorption reaction between xanthan gum-based biopolymer and Cd, Cu, Pb, and Zn was verified through contact time, initial concentration, and pH alteration. The biopolymer has a negative surface charge in the pH range of 1–8.5, and contains three dominant functional groups (i.e., OH, C-H, and CC bonds). The equilibrium time of Cd, Cu, Pb, and Zn concentration on the biopolymer was 10 min, and was followed by a pseudo-second-order kinetic reaction. The maximum sorption capacities (qm) of Cd, Cu, Pb, and Zn were 16.0 mg/g, 8.5 mg/g, 38.3 mg/L, and 7.2 mg/L, respectively. The Langmuir sorption isotherm was found to be more appropriate than the Freundlich model. Furthermore, the immobilization of heavy metals in the biopolymer-added soil was assessed using HCl and NaH2PO4 extraction. It was observed that 20% and 90% of Cu was immobilized in the soil, and the immobilization rate increased with the biopolymer mixing ratios. This study suggests that the biopolymer could be removed Cd, Cu, Pb, and Zn from solution, and the biopolymer could be applied as an additive for the immobilization of heavy metals in soil.