Generating cellulose-agar composite hydrogels for uptake-release kinetic studies of selenate and selenomethionine

Cellulose-agar (CAB) composite hydrogel beads were generated for the uptake-release kinetics studies of Se(VI) and selenomethionine (SeMt) from water medium. The objective of this work is to analyze the surface structure, gel properties, thermal stability and chemical functionalities responsible for the adsorption of Se(VI) and SeMt. We propose here a possible mechanism for the adsorptions. Adsorption isotherms are in good agreement with the Freundlich model, yielding a high adsorption capacity for the CAB composite. Maximum adsorption capacity of Se(VI) and SeMt were found to be 7.083 mg g^-1 and 34.639 mg g^-1 respectively. The mean free energy of adsorption (E*) value was found to be 0.0423 kJ mol^-1 and 0.329 kJ mol^-1 of Se(VI) and SeMt respectively. 1 M HCl and 0.1 M HCl were able to desorb Se(VI) and SeMt respectively from CAB. The adsorption of Se(VI) was significantly reduced if As(III), Cr(III) and Hg(II) were present as complementary ions in the medium. Similar studies with pristine cellulose beads (CB) yielded insignificant uptake properties.