Enhancing the metal ion binding characteristics and reversal of selectivity of crosslinked chitosan sorbents through functionalisation for targeted applications

A novel sponge composite of chitosan-sodium tripolyphosphate-melamine for anionic dye Orange II removal

Since the potential carcinogenic, toxic and non-degradable dyes trigger serious environmental contamination by improper treatment, developing novel adsorbents remains a major challenge. A novel high efficiency and biopolymer-based environmental-friendly adsorbent, chitosan‑sodium tripolyphosphate-melamine sponge (CTS-STPP-MS) composite, was prepared for Orange II removing with chitosan as raw material, sodium tripolyphosphate as cross-linking agent. The composite was carefully characterized by SEM, EDS, FT-IR and XPS. The influence of crosslinking conditions, dosage, pH, initial concentration, contacting time and temperature on adsorption were tested through batch adsorption experiments. CTS-STPP-MS adsorption process was exothermic, spontaneous and agreed with Sips isotherm model accompanying the maximum adsorption capacity as 948 mg∙g-1 (pH = 3). Notably, the adsorption performance was outstanding for high concentration solutions, with a removal rate of 97 % in up to 2000 mg∙L-1 OII solution (100 mg sorbent dosage, 50 mL OII solution, pH = 3, 289.15 K). In addition, the adsorption efficiency yet remained 97.85 % after 5 repeated adsorption-desorption cycles. The driving force of adsorption was attributed to electrostatic attraction and hydrogen bonds which was proved by adsorption results coupled with XPS. Owing to the excellent properties of high-effective, environmental-friendly, easy to separate and regenerable, CTS-STPP-MS composite turned out to be a promising adsorbent in contamination treatment.

Design of chitosan/boehmite biocomposite for the removal of anionic and nonionic dyes from aqueous solutions: Adsorption isotherms, kinetics, and thermodynamics studies

This study introduces a chitosan/boehmite biocomposite as an efficient adsorbent for removing anionic Congo Red (CR) and non-ionic Bromothymol Blue (BTB) from water. Boehmite nanoparticles were synthesized using the Sol-gel method and then attached to chitosan particles using sodium tripolyphosphate through co-precipitation method. Characterized through FTIR, FE-SEM, BET, and XRD, the biosorbent displayed structural integrity with optimized pH conditions of 3 for CR and 4 for BTB, achieving over 90 % adsorption within 30 min. Pseudo second order kinetics model and Langmuir isotherm revealed monolayer sorption with capacities of 64.93 mg/g for CR and 90.90 mg/g for BTB. Thermodynamics indicated a spontaneous and exothermic process, with physisorption as the primary mechanism. The biosorbent demonstrated excellent performance and recyclability over five cycles, highlighting its potential for eco-friendly dye removal in contaminated waters.