Chemical functionalization of Chitosan biopolymer with diacetyl monoxime for enhanced Cr(VI) removal from aqueous media

• Published in: International journal of biological macromolecules 2024-12, Vol.282 (Pt 3), p.137038, Article 137038
• Main Authors: Shekhawat, Anita, Gomase, Vaishnavi, Bambal, Apurva, Khapre, Maithili, Waghe, Prajakta, Saravanan, D., Jugade, Ravin
• Format: Article
• Language: English
• Subjects: Adsorption; Biopolymers - chemistry; Chitosan - chemistry; Chromium - chemistry; Chromium - isolation & purification; Column studies; Cr(VI) adsorption; Diacetyl - chemistry; Diacetylmonoxime; Hydrogen-Ion Concentration; Kinetics; Oximes - chemistry; Spectroscopy, Fourier Transform Infrared; Synthetic effluents; Temperature; Thermodynamics; Thiolated chitosan; Water - chemistry; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - isolation & purification; Water Purification - methods
• ISSN: 0141-8130; 1879-0003; 1879-0003
• DOI: 10.1016/j.ijbiomac.2024.137038

Hexavalent chromium is known for high toxicity as well as carcinogenicity and leads to contamination of water bodies through various anthropogenic activities. Chitosan biopolymer has limited adsorption capacity towards this toxicant. In order to boost hexavalent chromium adsorption, diacetylmonoxime was used to modify thiolated chitosan. The resulting material was extensively characterized using Fourier Transform Infrared, Energy Dispersive X-ray, Scanning Electron Microscopic and X-ray Diffraction investigations. To comprehend the adsorption mechanism in better way, various adsorption isotherms like Langmuir and Freundlich were investigated. In order to maximize the efficiency of adsorbent, response surface approach was used to optimize the several adsorption parameters, such as pH, adsorbent dose, adsorbate concentration, duration, and temperature. The results indicated that, 98 ± 0.5 % adsorption takes place at pH 5.0 with an adsorbent dosage of 20 mg and an adsorbate concentration of 20 mg L−1 at 298 K temperature within a short period of 60 min. According to the Langmuir monolayer isotherm, the material was observed to have Cr(VI) adsorption capacity of 430.73 mg g−1 under optimized operational conditions. Adsorption of Cr(VI) proceeds with pseudo-second-order kinetics. Because of the increasing unpredictability at interaction sites, it was discovered that adsorption efficiency decreased with rising temperature. Negative values of Gibbs free energy and enthalpy pointed towards the spontaneous and exothermic behaviour of the adsorption process. To find out if the material was suitable for greater sample volumes, column tests were conducted that showed excellent results for continuous column adsorption experiments. •Chitosan biopolymer was modified with thiourea and diacetylmonoxime to give DMCT.•DMCT was characterized and applied to Cr(VI) adsorption under different conditions.•Response surface methodology was applied for process optimization.•DMCT showed adsorption capacity of 430.73 mg g−1 with Langmuir isotherm•High adsorption capacity was attributed to strong ionic interactions due to hetero atoms.