Vanadium(V)/Mandelic Acid Initiated Graft Copolymerization of Acrylamide onto Guar Gum in an Aqueous Medium

ABSTRACT: The graft copolymerization reaction of acryl-amide onto guar gum with a vanadium(V)/mandelic acid redox pair was carried out in an N2 atmosphere. The opti-mum concentrations of vanadium(V), mandelic acid, hydro-gen ions, acrylamide, and guar gum for the maximum percentage of grafting were 6.0 103, 2.0 102, 55.0 102, and 20.0 102 mol/dm3 and 110.1 102 g/dm3, respectively. The optimum time and temperature of reaction were 90 min and 35C, respectively, and during the study of [Hþ] variation, a prompt change in the value of the grafting parameters was observed. The maximum percentage of swelling of the graft copolymer was achieved at room tem-perature in 1 h. Studies of the flocculation, viscosity, and metal-ion absorption capacity were also performed. The synthesized graft copolymer was characterized by Fourier transform infrared spectroscopy and thermogravimetric analyses, which showed that the grafted guar gum was ther-mally more stable than the ungrafted guar gum. VC 2009 Wile