Investigation on the Selective Adsorption of Mo(VI) by Using Modified Rice Husk and Corn Straw

The adsorption behavior, isotherms, kinetics and thermodynamics of molybdenum(VI) on modified rice husk (RH) and corn straw (CS) in an aquatic environment were investigated. The CS gel has shown a high affinity for Mo(VI) and selectivity toward its adsorption compared to Re(VII) and other base metals like Cu(II), Pb(II), Fe(III), Zn(II), Mn(II) and Ni(II). Adsorption mechanism of Mo(VI) onto the gels could be supposed to be the ion exchange and/or H-banding depending on the solution pH. The adsorption equilibrium for Mo(VI) on both the RH and the CS gel was best described by the Langmuir model. A kinetic study for the adsorption of molybdenum confirmed that it was endothermic adsorption process, which was further validated by thermodynamic data. Reutilization of both CS and RH gels was confirmed up to six adsorption-elution cycles in column-mode operation with no damage of gels, packed in the column. The result also provides a new approach for the removal of Mo(VI) (approximately 99.50 %) from Mo-containing surface water by using the modified rice husk and corn straw.