title: Sulfur crosslinks from thermal degradation of chitosan dithiocarbamate derivatives and thermodynamic study for sorption of copper and cadmium from aqueous system.
abstract: 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.
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA, 5095, Australia. yongsk@salam.uitm.edu.my.|Faculty of Applied Sciences, Universiti Teknologi MARA, 40450, Shah Alam, Selangor, Malaysia. yongsk@salam.uitm.edu.my.
authors.forename: Soon Kong
authors.identifier: http://orcid.org/0000-0001-9752-9127
authors.initials: SK
authors.lastname: Yong
authors.affiliation: Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA, 5095, Australia.
authors.forename: William M
authors.initials: WM
authors.lastname: Skinner
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA, 5095, Australia.
authors.forename: Nanthi S
authors.initials: NS
authors.lastname: Bolan
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA, 5095, Australia.
authors.forename: Enzo
authors.initials: E
authors.lastname: Lombi
authors.affiliation: Chemical Safety Division, Department of Agro-Food Safety, National Academy of Agricultural Science, Suwon-si, Gyeonggi-do, 441-707, Republic of Korea.
authors.forename: Anitha
authors.initials: A
authors.lastname: Kunhikrishnan
authors.affiliation: Korea Biochar Research Center and Department of Biological Environment, Kangwon National University, Chuncheon, 200-701, Republic of Korea.
authors.forename: Yong Sik
authors.initials: YS
authors.lastname: Ok
mesh_terms: D000327:Adsorption; D002104:Cadmium / Q000737:chemistry*; D048271:Chitosan / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000295:instrumentation / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D017550:Spectroscopy, Fourier Transform Infrared; D013455:Sulfur / Q000737:chemistry*; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
chemical_list: D014874:Water Pollutants, Chemical; D002104:Cadmium; D013455:Sulfur; D003300:Copper; D048271:Chitosan
keywords: Chemisorption; Chitosan; Mercapto group; Oxidation; Soft Lewis base; Thioamide