Optimization of anionic dye removal using cross-linked chitosan composite as eco-friendly bio-adsorbent

Abstract

The environmental impact of wastewater discharged from the textile dyeing industry has a significant challenge and influence on aquatic ecosystems and human health if not properly managed. This study aimed to develop a novel cross-linked chitosan composite, denoted as chitosan/fly ash/polyvinyl alcohol (Ch/FA/PVA), as a bio-adsorbent for removing Congo Red (CR) textile dye from industrial wastewater. The synthesis involved the incorporation of FA into the chitosan matrix at various ratios to optimize the process. A specifically tailored composite, Ch/FA0.75/PVA, exhibited superior performance with a remarkable 99.7% CR removal under optimum conditions: adsorbent dose (0.9 g/l), contact time (50 min), and dye concentration (40 mg/l). The characterization of Ch/FA0.75/PVA through SEM–EDX, BET, FTIR, and pHzpc confirmed its suitability for adsorption. Employing Box–Behnken design and analysis of variance (ANOVA) facilitated the optimization of key adsorption variables. The Freundlich model described the adsorption equilibrium, indicating a maximum adsorption capacity of 263.15 mg/g for CR dye. The pseudo-second-order model demonstrated favorable kinetics. The study was scaled up to the practical application of Ch/FA0.75/PVA in a pilot plant for industrial wastewater treatment, revealing substantial removal percentages for dye, color, COD, BOD5 and TDS. This comprehensive approach highlights the promising efficacy of Ch/FA0.75/PVA in addressing environmental concerns associated with textile dye wastewater.