Insight into adsorption kinetics and isotherms for adsorption of methylene blue using gum rosin alcohol/psyllium-based green adsorbent

Abstract

Present work focused on synthesis of green hydrogel polymer of gum rosin alcohol/psyllium crosslinked poly (acrylic acid) [(GrA-Psy)-cl-PAA] under vacuum condition. Use of both psyllium and gum rosin alcohols as backbones could lessen the burden on the environment, as more natural aspect is drawn in the hydrogel polymer. The various reaction parameters for the synthesis of hydrogel polymer were systematically optimized as a function of percentage swelling. The optimized ecofriendly hydrogel polymer was characterized using XRD, FTIR, FE-SEM and TGA techniques, which supported the successful formation of crosslinked three-dimensional network structures. (GrA-Psy)-cl-PAA was further studied as an adsorbent for the removal of methylene blue dye from an aqueous solution. Adsorption parameters such as the amount of adsorbent and pH were optimized to obtain the maximum percentage of dye removal. Kinetics of the adsorption process was analyzed using pseudo-first-order, pseudo-second-order and Elovich kinetic models. Adsorption kinetics followed pseudo-second-order model (non-linear) for all the concentrations studied. Non-linear forms of Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich isotherm models were studied for the adsorption process and it was observed that it goes well with both Langmuir and Freundlich isotherms. Thermodynamic parameters were also evaluated which indicated that the adsorption process was exothermic and spontaneous. Furthermore, the candidate polymer retained a reusability tendency for two consecutive cycles of adsorption/desorption. Thus, the synthesized novel material was taken as a potential to act as green adsorbent in treatment of industrial wastewater.