Chitosan-Based Biopolymer for Efficient Cr(VI) Removal: A Thermodynamic and Adsorption Study

Abstract

Chitosan biopolymer was utilized without modification to separate hexavalent chromium Cr(VI) ions from liquid feed. Cr(VI) contamination in water poses a critical environmental and health concern due to its toxicity and persistence, necessitating effective and sustainable removal methods. This study investigates the use of chitosan biopolymer as an environmentally friendly adsorbent for Cr(VI) removal. Batch experiments were conducted to investigate the effects of adsorbent dose, pH, contact time, and temperature. The optimal conditions achieved were as follows: 50 mg adsorbent dose, pH 6, 70 minutes contact time, 15 mg/L Cr(VI) concentration, and 30°C, with a maximum removal capacity of 66.64 mg/g. The Langmuir isotherm Model (R² = 0.9981) indicated monolayer adsorption, while pseudo-first-order kinetics confirmed a physio-adsorption mechanism. Thermodynamic analysis revealed an exothermic process (ΔH° = -15.617 kJ/mol) with a negative ΔS° (kJ/mol·K), indicating a reduced randomness at the solid-liquid interface and confirming predictable adsorption behavior. The results highlight the potential of chitosan biopolymer as a sustainable solution for Cr(VI) removal, with promising applications in environmental remediation.