Defluoridation of aqueous solutions by nanocomposite of MgAl2O4 and MA-VA-AA polymer: kinetics and mechanism

摘要

A nanocomposite of co-precipitatively synthesized MgAl2O4 and methyl acrylate-vinyl acetate-acrylic acid polymer was prepared through radical polymerization mechanism. The synthesized material was characterized by XRD, TGA, DSC, and SEM. XRD analysis of magnesium aluminate confirms the single spinel phase with average crystallite size of 33 nm. Adsorption of fluoride on the nanocomposite was studied at 308 K. The adsorption data were fitted to Freundlich, Langmuir, and Flory-Huggins models. Better correlation and comparable values of theoretical and experimental adsorption capacities (q(e)) indicated that the adsorption process followed pseudo-second-order kinetics. Mechanism of the adsorption process was investigated by applying Bingham's and intraparticle diffusion models. Deviation from linearity of Bingham's plot and significant value of intercept obtained from intraparticle diffusion model showed that both the film diffusion and pore diffusion processes may be the rate-controlling steps. Moreover, 96% successful removal of the fluoride by the synthesized nanocomposite, suggest it to be a suitable adsorbent for defluoridation of aqueous solutions.