Optimization of synthesis conditions for graft copolymerization of methacrylic acid onto Garcinia kolapods and use in the sequestration of cationic dyes from simulated wastewaters

This report describes the grafting of methacrylic acid (MAA) onto Garcinia kolapods (GKP) and its utilization in the sequestration of methylene blue (MB) and malachite green (MG) from aqueous medium. The synthesis method involved the use of a simple reactor containing N2gas inlet and outlet. Free radicals were initiated by ammonium persulfate. With 2 g MAA, 33% grafting yield was obtained after 2 h, at 60 ℃, and with 0.01 mol L−1initiator. Material characterization was done by FTIR, SEM, XRD, and TGA, with all confirming the success of the grafting process. During the sorption process, solution pH, contact time, initial dye concentration, and temperature were varied. Rise in each of these parameters favored the sorption process up to their optimum states. With 0.1 g GKP-g-MAA, about 96% MB and 93% MG were removed. The adsorption process followed the pseudo-second-order kinetic model, while isothermal data fitted the Redlich-Peterson model best with R2values of 0.9994 and 0.9991 for the sorption of MB and MG, respectively. This was followed by Langmuir, indicating a homogeneous system and a reaction-controlled process. Thermodynamic data portrayed the sorption process as being feasible, spontaneous, endothermic, and characterized with increased disorderliness. Elovich model suggested the contribution of chemisorption; mean free energies, E˂ 8 k Jmol−1, indicated physisorption, while enthalpy change, ΔH°, depicted physisorption and the contribution of weak chemisorption in the sorption of MB and MG, respectively. Regeneration of the material was efficient, while high % dye removal showed a great adsorbent potential in the copolymer.