Sulfur crosslinks from thermal degradation of chitosan dithiocarbamate derivatives and thermodynamic study for sorption of copper and cadmium from aqueous system

• Published in: Environmental Science and Pollution Research
• Main Author: Yong S.K.; Skinner W.M.; Bolan N.S.; Lombi E.; Kunhikrishnan A.; Ok Y.S.
• Format: Article
• Language: English
• Published: Springer Verlag 2016
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954404575&doi=10.1007%2fs11356-015-5654-5&partnerID=40&md5=5f61585ea698b764eabae770b4831c7c

Pristine chitosan beads were modified with sulfur (S)-containing functional groups to produce thiolated chitosan beads (ETB), thereby increasing S donor ligands and crosslinks. The effect of temperature, heating time, carbon disulfide (CS2)/chitosan ratio, and pH on total S content of ETB was examined using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The total S content of ETB increased with increasing CS2/chitosan ratio and decreased with decreasing pH and increasing temperature (>60 °C) and heating time (at 60 °C). Spectroscopic analyses revealed the presence of thiol (–SH)/thione, disulfide (–S–S–), and sulfonate groups in ETB. The thiolation mechanism involves decomposition of dithiocarbamate groups, thereby forming thiourea crosslinks and trithiocarbonate, resulting in –SH oxidation to produce –S–S– crosslinks. The partially formed ETB crosslinks contribute to its acid stability and are thermodynamically feasible in adsorbing Cd and Cu. The S-containing functional groups added to chitinous wastes act as sorbents for metal remediation from acidic environments. © 2015, Springer-Verlag Berlin Heidelberg.