Modification of guar gum through grafting of acrylamide with potassium bromate/thiourea redox initiating system

In the present work, graft copolymers of acrylamide onto guar gum were synthesized by free radical polymerization using potassium bromate/thiourea redox initiating system. The guar gum and guar gum-g-polyacrylamide were characterized by infrared spectroscopy and thermogravimetric analysis. It was found that the guar gum-g-polyacrylamid was thermally more stable than pure guar gum. The grafting ratio, grafting efficiency, add-on, and conversion increased with the concentration of bromate and acrylamide, whereas they decreased with increasing the concentration of guar gum. The grafting ratio and grafting efficiency showed maximum value at the concentration of thiourea and hydrogen ions of 3.2×10^-3 mol dm^-3 and 4.0×10^-3 mol dm^-3, respectively, but decreased with further increasing the thiourea and hydrogen ions concentrations. The increase in temperature from 30 to 45 °C resulted in increasing the grafting ratio while decreasing the conversion. The optimum reaction time for the graft copolymerization was found to be 2 h. Compared to the parent guar gum, the graft copolymer showed higher water swelling capacity and metal ion sorption, as well as better flocculant behaviors.