Benzoxazine-sulfur-Chitosan based freestanding beads: Synthesis, characterization, stability, and removal of mercury and oil

Abstract

Environmentally benign dual-functional sorbents are desired for easy removal of various and variably located pollutants such as heavy toxic metal ions and crude oil from water. Herein, we have developed sorbents based on sustainable feedstocks using a facile methodology. Bulk copolymerization of biobased benzoxazine (C-fa, cardanol ‘C’ and furfurylamine ‘fa’) with elemental sulfur (S, industrial waste) proceeded in a single step (10 min) to form poly(benzoxazine-ran-sulfur). Bare chitosan (CS) beads and CS/poly(benzoxazine-ran-sulfur) composite beads are fabricated, and performance is analyzed. CS/poly(benzoxazine-ran-sulfur) beads reveal good mechanical and hydrolytic stability, and effectively remove crude oil (8-times the sorbent weight) with appreciable recyclability. These composite beads also demonstrated well-defined mercury ion uptake kinetics, along with a very high mercury ion capture capacity of 334.5 mg of mercury per gram of polymer as calculated from the Langmuir isotherm model and followed a pseudo-second-order kinetics. Designed waste-derived sorbents hold a great promise in tackling the diverse nature of pollutants essential for water purification.