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Simultaneous detection of heavy metal and cationic dye from aqueous solution by hydrogel of poly(acrylic acid) grafted onto chitosan

Mohammed Mizanur Rahma

Poly(acrylic acid) (PAA) has been grafted to chitosan at varying ratios in order to prepare the hydrogel adsorbent to remove Cr(VI), Pb, and methylene blue from the waste water solution. The reaction was performed in a homogeneous aqueous phase using N, N-methylenebisacrylamide (MBA) as a cross-linker, and ammonium persulfate as an initiator. Grafting (%) decreases with an increase in the quantity of chitosan in the hydrogel, but the degree of swelling increases slightly with an increase of chitosan due to the amphiphilic nature of the modified chitosan. The hydrogel was characterized by a variety of techniques, such as FT-IR, SEM and TGA analysis. Adsorption behaviors for Cr (VI), Pb, and methylene blue (MB) on the prepared adsorbent were studied with respect to the standard solution and the actual industrial effluent sample. Maximum removal efficiencies for Cr(VI) and Pb were obtained from 2:1 chitosan and acrylic acid (AA) in the hydrogel. On the other hand, hydrogels with higher PAA had a remarkably higher MB adsorption capacity than others. Increased removal of heavy metals and MB by the hydrogel than chitosan was due to carboxyl groups that are easy to form bidentate carboxylates with metal ions. The adsorption result of the hydrogel for real industrial effluent showed that approximately 35% of heavy metals (Cr (VI), Pb) and 53 % MB can be removed by a single adsorption cycle.