Chemistry of defluoridation by one-pot synthesized dicarboxylic acids mediated polyacrylamide-zirconium complex

The current report deals with the synthesis of a new and excellent fluoride sorbents using dicarboxylic acids like oxalic acid (Ox) malonic acid (MA) and succinic acid (SA) mediated polyacrylamide-zirconium (PAAm-Zr) and zirconium-oxalic acid (Zr-Ox) complexes by one-pot method. Among the synthesized complexes, Ox-PAAm-Zr and Zr-Ox complexes showed higher (double the times) defluoridation capacity (DC) than the other complexes under batch equilibrium mode. Characterizations of the synthesized complexes were carried out to determine the functional groups, surface morphologies, elemental analysis and crystalline nature. Various equilibrium parameters were optimized. The sorption data were well explained by three commonly used isotherms viz., Freundlich, Langmuir and D-R isotherms. Thermodynamic parameters like δG°, δH° and δS° were calculated and predicted the nature of the fluoride adsorption is spontaneous and endothermic. The mechanism of fluoride removal using Ox-PAAm-Zr complex is ligand-exchange mechanism. Suitable regenerant has been identified in desorption studies and the regeneration ability was tested. Also, the practical viability of the material has been verified with field samples collected from nearby fluoride endemic villages. © 2014 Elsevier B.V.