Potential of easily available low-cost raw cotton for the elimination of methylene blue dye from polluted water

Abstract

This study centered on exploring the adsorptive potential of the raw cotton for methylene blue dye adsorption. Several laboratory experiments conducted to optimize operational factors like pH, concentration of dye, adsorbent dose, contact time, and temperature. Optimized conditions of the study include an adsorbent dose of 0.35 g, pH of 7, an initial dye concentration of 20 ppm with contact time of 30 min at 20 ºC wherein 83% of adsorption take place. The mean values ± standard deviation from triplicate experiments were used to express the results with P < 0.05. The investigational data fit well with the Langmuir isotherm model having R2 of 0.9477 and pseudo second order kinetic model having R2 = 1. The values obtained for adsorption capacities through non-linear models exhibit a significant degree of similarity with those derived from linear models. Thermodynamic study showed a negative ∆G, positive ∆H and increased ∆S values revealing that the reaction was spontaneous and endothermic in nature. The developed method was also tested with tap water which showed 72% of dye removal and subsequent regeneration of the system led to nearly 79% desorption of the dye. Results of the study revealed that additive salts had a minimum effect on the adsorption process. The originality of this study is that no research has been reported till yet, for adsorption of methylene blue by using low-cost raw cotton specifically in its non-modified form.