Abstract
Dextrin as a biodegradable natural polymer has hydrophilic nature that capable to increase the swelling properties and biodegradability of the synthetic hydrogels. This study describes the synthesis of a poly (acrylic acid-co-acryloyl tetrasodium thiacalix[4]arene tetrasulfonate) grafted dextrin superabsorbent hydrogels (ADA) via solution polymerization. The effects of acryloyl tetrasodium thiacalix[4]arene tetrasulfonate (ACSTCA) dose (20–60) on swelling properties of the hydrogels were studied. The synthesized hydrogels were characterized by FTIR, TGA, DMTA and rheometry. The metal ion removal capacity of the gels was investigated by atomic absorption for Cd2+, Pb2+, and Hg2+. The tendency of metal ions adsorption decreased in the order of Pb2+>Cd2+>Hg2+. The effect of key operating parameters including ACSTCA content, contact time, adsorbent dosage, solution pH, and crosslinker density was experimentally studied on Pb2+ adsorption from aqueous solution. The equilibrium data was analyzed using Langmuir and Freundlich adsorption isotherms. Our experimental data are in best agreement with Freundlich isotherms, and adsorption of metal cation onto hydrogel followed a pseudo second-order kinetic model. According to the thermodynamic parameters, the adsorption of Pb2+ occurred spontaneously. The hydrogels could be regenerated after releasing heavy metal ions, and reused 5 times with less than 7 % loss of adsorption capacity.
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