Efficient adsorption of crystal violet (CV) dye onto benign chitosan-modified l-cysteine/bentonite (CS-Cys/Bent) bionanocomposite: Synthesis, characterization and experimental studies

Abstract

Crystal violet (CV) a cationic dye is more harmful than anionic dye. CV is employed in many industries, including leather, paper, pharmaceutical, textile, and cosmetics. It causes several harmful effects like eye and skin irritation; in extreme situations, it causes renal and kidney or respiratory failure. Because it is non-biodegradable, this dye sticks to the aquatic environment for a very long period. Therefore, it is important to remove this dye from wastewater to prevent its contamination to normal water bodies. This study evaluated the performance of Chitosan-modified l-cysteine/Bentonite (CS-Cys/Bent) bionanocomposite for the adsorption of CV dye. To investigate the surface morphology and potential interaction between the (CS-Cys/Bent) bionanocomposite and CV dye, the (CS-Cys/Bent) were characterized by TEM, SEM-EDX, FTIR and XRD techniques. At pH-8, with 0.01 g of adsorbent dosage, and an optimal duration of 180 min, the maximum adsorption capacity (85.13 mg/g) was observed. The maximum adsorption capacity was 219, 237, and 240 mg/g at 303, 313 and 323 K. The experimental data were subsequently examined using a variety of isotherm models; with the highest R2 values (0.990, 0.983 and 0.984 at 303, 313 and 323 K, respectively), the Freundlich model was the best fitted model. Among the kinetics models, pseudo-second order (PSO) was the best-described kinetic model with the highest coefficient (R2, 0.999). The positive values of ΔS° (0.037 kJ/mol.K) and ΔH° (7.148 kJ/mol) demonstrated the process to be spontaneous and endothermic. The (CS-Cys/Bent) can be successfully recycled up to the fourth cycle.