Functionalized chitosan and sodium alginate for the effective removal of recalcitrant organic pollutants

Abstract

In this work, the study of an oxidative-coupling reaction by immobilization of laccase or horseradish peroxidase (HRP) onto chitosan and sodium alginate was reported. The oxidative-coupling reaction of three recalcitrant organic pollutants (ROPs) such as chlorophenol compounds including 2,4-dichlorophenol (DCP), 2,4,6- trichlorophenol (TCP), pentachlorophenol (PCP) was studied. The results showed that the systems with immobilized laccase or horseradish peroxidase had broader range of optimum pH and temperature when compared to that of free laccase and horseradish peroxidase. The removal efficiencies of DCP, TCP and PCP within 6 h were found to be 77 %, 90 % and 83 %, respectively. The rate constants of the first order reactions for laccase were arranged as 0.30 h−1 (TCP) > 0.13 h−1 (DCP) > 0.11 h−1 (PCP) and the rate constants for HRP were arranged as 0.42 h−1 (TCP) > 0.32 h−1 (PCP) > 0.25 h−1 (DCP). The removal rate of TCP was found to be the highest among all and the removal efficiency of ROPs by HRP was always better than that of laccase. The major products of the reaction were identified by LC-MS and confirmed as humic-like polymers.