Preparation of chitosan-g-pmma for adsorption-desorption behavior of urea

Abstract

This study focused on grafting of poly(methyl methacrylate) (PMMA) onto chitosan beads to develop a controlled-released fertilizer material which can act as carrier molecule for fertilizers. Chitosan grafted with PMMA (chitosan-g-PMMA) was successfully synthesized using potassium persulfate (KPS) as the initiator and characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy and X-ray diffraction (XRD). Grafting yield of 51.47% was obtained at 70ºC, 6.58 ? 10-3 mol/L of KPS and 1 mL of monomer. FTIR results showed successful grafting between PMMA and amino group of chitosan through the increasing intensities observed in the absorption peaks at 1726 and 1147 cm-1. Surface morphology of the beads showed that grafted chitosan bead has smoother surface compared to pure chitosan bead and XRD spectrum for chitosan-g-PMMA bead also showed a shift of 2? due to the grafting of PMMA onto the chitosan backbone. The maximum amount of water absorbed into the chitosan beads is 5.70 g after 80 minutes of immersion whereas grafted chitosan beads only adsorbed 1.25 g of water even after 180 minutes of immersion indicating that grafted chitosan beads showed a slow increase in degree of swelling compared to pure chitosan beads. The optimum time for maximum adsorption of urea into the chitosan beads was found to be at 12 hours with 0.33% urea adsorption whereas grafted chitosan beads has maximum adsorption at 24 hours which is 0.24% of urea. Desorption of urea from the chitosan beads showed that more than 90% desorption of urea occurred within 6 hours compared to grafted chitosan beads in which desorption occurred more than 24 hours. As the structure of both beads still remain unchanged even after adsorption and desorption of urea, the beads can be recycled.