Application of crosslinked chitosan-nanoclay composite beads for efficient removal of Ponceau S azo dye from aqueous medium

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In this study, chitosan-nanoclay composite beads (CS/NC composite beads) were used to remove Ponceau S from aqueous solutions. CS/NC composites characterization was performed with FTIR, SEM-EDX, TGA, BET and XRD analyzes. The adsorption procedure was optimized by changing various parameters in batch experiments such as pH, dye concentration, contact time and temperature. Ponceau S adsorption took place at a higher rate in the acidic region, and the highest adsorption was observed at pH 2.0. The amount of adsorbed dye increased as the temperature increased at low dye concentrations and the time required to reach equilibrium was shorter than at higher dye concentrations. Linear and non-linear forms of Langmuir, Freundlich and Temkin adsorption models were applied. The adsorption behavior of Ponceau S is compatible with the linear Langmuir model, and the maximum adsorption capacity was found to be 140.85 mg g-1. Linear and nonlinear forms of adsorption kinetics and thermodynamic parameters were investigated for dye concentrations of 150-400 mg/L. The adsorption kinetics fit the linear pseudo-second-order kinetic model and the Ponceau S adsorption on CS/NC composites was spontaneous and endothermic. The results show that the CS/NC composites can be used as an effective adsorbent in industrial wastewater treatment.