Synthesis and characterization of novel guar gum hydrogels and their use as Cu2+ sorbents.

To prepare novel hydrogels for use in water technologies, guar gum was subjected to acid hydrolysis. The depolymerized guar gum obtained there from and the native guar gum were oxidized to their respective polycarboxylic forms using NO(x) as oxidant. All these polymers were crosslinked with N,N-methylenebisacrylamide, and were used as Cu(2+) sorbents. The candidate hydrogel exhibiting the highest uptake was used further to investigate the effect of external stimuli on sorption. The sorption on hydrogels was fast as the highest sorption was observed after 2 h at 40 degrees C and 20 ppm of Cu(2+) ions. The hydrogel prepared from the oxidized guar gum afforded the maximum sorption capacity of 125.893 mg g(-1). Langmuir and Freundlich isotherms, and pseudo second order kinetics matches the experimental data. The evidence of sorption was obtained by characterizing Cu(2+)-loaded hydrogels by FTIR spectroscopy.