Effective removal of malachite green dye by eco-friendly pectin-grafted poly(acrylamide-co-sodium acrylate) hydrogel from aqueous solutions

Abstract

Grafting of copolymer of sodium acrylate (SA) and acrylamide (Am) onto pectin (Pcn) was successfully performed in order to synthesis Pcn-g-P(Am-co-SA) hydrogel using combined microwave-assisted method and potassium persulfate (KPS) as a free radical initiator. The prepared hydrogel was characterized by FTIR, SEM and TGA. This hydrogel was used to remove malachite green (MG) dye from aqueous solutions. The swelling ratio of the best grade of hydrogel was 214 g/g at pH (7). Factors affecting MG dye adsorption on hydrogel (grafting percentages, pH, contact time, hydrogel dosage, dye initial concentration and temperature) were studied, and the reusability study was also investigated which, in turn, showed the high adsorption capacity of hydrogel for MG dye. The adsorption data were fitted well with Langmuir adsorption isotherm model proposing the formation of monolayer of MG dye molecules on the hydrogel’s surface with maximum adsorption capacity (5000 mg/g). Moreover, the thermodynamic studies indicated the spontaneity and exothermic nature of adsorption of MG dye on hydrogel. From the reusability study, it was found that the prepared hydrogel still retains good adsorption properties after eleven successive cycles. Therefore, Pcn-g-P(Am-co-SA) hydrogel was considered as a highly potential adsorbent for MG dye removal from aqueous solutions.