Study of the biosorption of reactive dyes on cellulosic waste from the textile industry.

Abstract

In this study, waste denim (JW) was investigated as an adsorbent for the removal of methylene blue from aqueous solutions. The denim waste was chemically modified using sodium thiosulfate (Na2S2O3), resulting in a modified adsorbent (JW-Na2S2O3) with substantially enhanced adsorption performance compared with untreated waste denim (JW). The JW-Na2S2O3 material achieved a maximum removal rate of approximately 99.5% at an initial concentration of 5 mg/L, compared to 54% for the JW material. This improvement can be attributed to changes in the surface functional and chemical properties of the adsorbent, as evidenced by Fourier-transform infrared spectroscopy (FTIR), Boehm titration, and determination of the point of zero charge (pHpzc). Statistical analysis using analysis of variance (ANOVA) in conjunction with response surface methodology based on a Box–Behnken design (BBD) demonstrated that pH, adsorbent dosage, and initial dye concentration, as well as the interaction between pH and adsorbent dosage, had statistically significant effects on the adsorption process (p < 0.05). Equilibrium analysis indicated that the Freundlich isotherm provided the best fit to the experimental adsorption data compared with the other models

investigated. Furthermore, the adsorption kinetics were better described by the pseudo-first- order kinetic model. Finally, the thermodynamic study showed that the adsorption process of

the raw material (JW)is an endothermic process, while it turned into an exothermic process after modification for the material (JW-Na2S2O3).