RADIATION SYNTHESIS OF POLY(CHITOSAN/ACRYLAMIDE) HYDROGEL FOR REMOVAL OF NIGROSIN FROM ITS AQUEOUS SOLUTION

Chitosan hydrogels were prepared by gamma radiation grafting of acrylamide (AAm) onto chitosan (CS). The gelation (%) increased as the AAm content was raised up to the CS/AAm ratio of 1/10 wt%. The grafting yield and the grafting ratios of the Poly(CS/AAm) hydrogel were found to be directly proportional to the increase in AAm contents. The swelling behavior was more pronounced with higher AAm content up to 1/15 wt% in the Poly(CS/AAm), and then decreased with further rise of the AAm content to 1/20 wt%, because of the formation of a highly crosslinked hydrogel, with high hydrogen bonding. The prepared Poly(CS/AAm) hydrogels were characterized by using FTIR, TGA and SEM techniques. The analysis confirmed successful preparation of Poly(CS/AAm) with different compositions. The adsorption capacity of the Poly(CS/AAm) hydrogel with the composition of (1:10 wt%) towards Nigrosin acid dye was found to be higher than that of the other hydrogel formulations. This may be due to the fact that the selected Poly(CS/AAm) hydrogel possesses a highly pronounced swelling behavior and a highly crosslinked structure, compared to the other prepared hydrogels. It has been also noted that the adsorption capacity of the 1:10 wt% Poly(CS/AAm) hydrogel enhanced markedly at pH 2, but decreased at higher pH values, namely, from pH 5 to pH 7.4. This can be explained by the protonation of amide groups of acrylamide and amine groups of chitosan occurring at lower pH. The high adsorption properties of the selected Poly(CS/AAm) hydrogel recommend it as a necessary bioremediation solution to face the high level of acid dye pollutants, such as Nigrosin, in industrial effluents.