Removal and adsorption kinetics of methylene blue dye by pristine cotton husk bracts (Gossypium hirsutum L.) from agroindustrial waste

Abstract

In the present study, pristine cotton husk bracts (CHk), an agricultural waste, were successfully employed as an adsorbent for the removal of methylene blue (MB). Batch adsorption experiments were performed as a function of contact time, pH, adsorbent dosage, and initial dye concentration (1–100 mg/L). The experimental results indicate that 20 mg of CHk removed 94% of 20 mg/L dye. Adsorption dye kinetic was analyzed using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. Furthermore, adsorption data were modeled using the Langmuir, Freundlich, and Temkin isotherms. The kinetic study reveals that the present adsorption process followed a pseudo-second-order, with a qe= 96.56 mg/g and, k2 = 0.109 min−1 at pH 7. Adsorption followed the Langmuir isotherm; the adsorption equilibrium results show a qm = 458.72 mg/g and kL= 0.1622 L/mg, using 20 mg of CHk. The equilibrium parameter value (RL) was observed to be in the interval of 0.0580 to 0.8604. Thermodynamic results indicate that the adsorption mechanism between CHk and MB is spontaneous, exothermic, and with a decrease in the disorder of the adsorbate molecules on the adsorbent surface; at all the temperatures studied (293, 313, 333 K). The use of CHk agroindustrial waste is an ideal option for the treatment of industrial textile effluent in environmental cleansing.