Synthesis of partially carboxymethylated guar gum-g-4-vinyl pyridine and study of its water swelling, metal ion sorption and flocculation behaviour

Unreported graft copolymer of 4-vinyl pyridine (4VP) with partially carboxymethylated guar gum (Cmg) was synthesized and reaction conditions were optimised using a bromate/thiourea redox pair under an inert atmosphere at 40 °C. Studies have been done to observe the effect of reactants on grafting parameters by varying the reactant concentration. Grafting ratio, add on and conversion show a decrement on increasing the concentration of partially carboxymethylated guar gum beyond 1.0 g dm−3. The grafting parameters increase on increasing the concentration of 4-vinyl pyridine from 13 × 10−2 to 25 × 10−2 mol dm−3, BrO3- from 4 × 10−3 to 10 × 10−3 mol dm−3 and thiourea from 1.6 × 10−3 to 4.8 × 10−3 mol dm−3. Optimum temperature and time for grafting of 4-vinyl pyridine on partially carboxymethylated guar gum are found to be 40 °C and 120 min, respectively. Metal ion uptake and flocculation behaviour have been also studied and found that graft copolymer shows enhancement in these properties than substrate. Swelling behaviour of graft copolymer has been investigated. The graft copolymer is characterized by FTIR and thermal analysis.