Microwave synthesis, characterization, and zinc uptake studies of starch-graft-poly(ethylacrylate)

Microwave synthesis of starch-graft-poly(ethylacrylate) was optimized to obtain efficient Zn(II) adsorbent that has been characterized using IR, XRD and SEM analyses. Using the sample, adsorption of Zn(II) was studied as a function of pH, sorbent dose, initial Zn(II) concentration, % grafting, temperature and ionic strength. Equilibrium isotherm data were analyzed using the Langmuir and Freundlich isotherms at optimum pH (pH 8) where the data fitted satisfactorily well to both the isotherms indicating sorption of Zn(II) on the copolymer was complex and involved more than one mechanism. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy, and entropy of sorption. At 30 °C, the maximum sorption capacity of the microwave synthesized copolymer was 172 mg g−1 as compared to 116 mg g−1 for the conventionally synthesized starch-graft-poly(ethylacrylate) indicating the advantage of using microwaves in the copolymer synthesis. In order to investigate the mechanism of sorption,kinetic data were modeled using the first order Lagergren, pseudo-second-order and intra-particle diffusion models where chemisorption seem significant in the rate controlling step. The regeneration experiments revealed that the starch-graft-poly(ethylacrylate) can be successfully reused for five cycles without any significant loss in the sorption capacity.