Sorption behavior of Molybdenum (IV) onto commercial acidic alumina surface

The study investigated the adsorption behavior of molybdate on acidic alumina at different pH values, contact times, initial molybdenum concentrations, and reaction temperatures. The batch capacity of the commercial acidic alumina was determined by batch method at 25 o C from 0.005 M sodium molybdate solution and was found to be 45 mg /g. The sorption data was fitted to the Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) sorption isotherms, and the mean sorption energy was found to be 9.243 kJ/mol. For the kinetic analysis, the Lagergren equation was applied, and the pseudo-second-order kinetic model offered excellent data fitting for molybdenum uptake. The standard enthalpy was found to be -6.2 kJ/mol after calculating the thermodynamic constants. The calculated ∆G° were - 12.42, -12.635, and - 13.126 kJ mol -1 at all experimental temperatures. While the standard entropy was found to be 20.67 J mol -1 . The results show that the sorption process is exothermic and spontaneous, with a higher degree of ion freedom.