Effect of microwave on the synthesis of polyacrylamide-g-chitosan gel for azo dye removal

Effective dye removal is of crucial importance for the well-being of the environment and human health, and hydrogels are top-players for this goal. In this work, hydrogels of polyacrylamide grafted onto chitosan, crosslinked with N,N'-methylenebisacrylamide, were synthesized by conventional (CM) and microwave-assisted methods (MWM). The products were characterized by Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy and swelling capacity. The developed hydrogels were evaluated as an adsorbent for the azo dye Acid Blue 113. MWM provided higher yield of the product with reduced reaction time when compared to the CM. The dye removal efficiency by MWM was slightly lower than that observed by CM, but MWM showed a much higher maximum adsorption capacity than the conventional one. The adsorption behavior of conventional and MW hydrogels followed the Langmuir and Freundlich models, respectively. The MW hydrogel presented the best characteristics to be used as an adsorbent of the AB 113 dye.