Graft copolymerization of acrylonitrile onto delignified native bamboo (Bambusa vulgaris) cellulosic and its utilization potential for heavy metal uptake from aqueous medium

Abstract

Graft polymerization of acrylonitrile onto delingnified cellulosic material obtained from Nigeria grown Bamboo (Bambusa vulgaris) could be initiated by ceric ammonium nitrate redox system. Optimization of grafting of acrylonitrile onto cellulosic material was performed by varying the reaction conditions, such as duration of soaking of cellulosic material in ceric ammonium nitrate solution, concentration of ceric ammonium nitrate solution, polymerization time, temperature of reaction, acrylonitrile concentration and saponification time; to study their influence on percent grafting yield and grafting efficiency. The resulting cellulosic-g-polyacrylonitrile (PAN) copolymers were fractionated by extraction at 33?C with N,N? dimethyl formamide. Fractions were characterized by determining both the % add-on and the free polymer. Saponification of grafted copolymer was done by reaction with sodium hydroxide followed by methanol precipitation. The absorbent polymer so produced gave a fair water retention values. The optimum reaction conditions obtained were: 20mmol/l ceric ammonium nitrate solution in 1% nitric acid, soaking duration of 0.5h at 40?C for a polymerization time of 2h and saponification time of 3h.The percent grafting is 167.89%, grafting efficiency is 93.52% and water retention value is 389g/g. The grafting was confirmed using FTIR. Sorption of different metal ions in the mixture e.g. Cr, Mn, Ni, Cu and Pb by grafted cellulosic and the hydrogel was also investigated. Hydrolysis increases the sorption affinity of grafted cellulose toward water and metal ions.