Gamma radiation-induced grafting of glycidyl methacrylate to water hyacinth fibers: functionalization and metal ion uptake kinetics

Water hyacinth fibers (WHF) were functionalized using gamma radiation-induced graft polymerization of glycidyl methacrylate (GMA) to obtain fibers with oxirane groups for chemical modification. The simultaneous grafting technique was employed wherein the WHF were irradiated in nitrogen atmosphere in the presence of GMA dissolved in water/methanol solvent. The effects of different grafting parameters to the grafting yield were evaluated. The optimal values of solvent, radiation absorbed dose, dose rate, concentration of monomer were found to be 1:3 (volume/volume) water-methanol solvent, 10 kGy, 8 kGy hour -1 dose rate and 5% (volume/volume) GMA, respectively. Using the optimum conditions, grafting yield approximately 58% was achieved. The GMA grafted WHF were subsequently modified with ethylenediamine and sodium sulfite. The resulting amine and sulfonic acid functionalized WHF, together with the grafted WHF, were characterized using Attenuated Total Reflectance-Fourier Transformed Infrared Spectroscopy (ATR-FTIR). Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). The sorption of Cu2+, Cr3+ and Pb2+ ions on the amine functionalized WHF was studied. The initial concentration of the metal ions and pH of the solution were found to have important effect on the adsorption of the metal ions onto the amine functionalized WHF. The kinetics of adsorption was observed to follow Lagergren first order equation. Results of ion sorption studies indicate that radiation induced grafting and subsequent chemical modification improved the ion sorption behavior of WHF. (author)