Studies on Mg/Fe hydrotalcite-like-compound (HTlc) I. Removal of inorganic selenite (SeO3(2-)) from aqueous medium

A Mg/Fe hydrotalcite-like-compound (HTlc) was prepared and its affinity toward the removal of SeO(3)(2-) from an aqueous medium was studied as a function of pH, time, temperature, particle dose, and SeO(3)(2-) concentration. The fraction of SeO(3)(2-) removal increases with decrease in both pH and temperature. The adsorption data are fitted to the Langmuir adsorption isotherm in the temperature range 303-333 K, and the thermodynamic parameters viz. standard Gibbs' free energy change (DeltaG degrees ), enthalpy change (DeltaH degrees ), and entropy change (DeltaS degrees ) are calculated. The negative value of DeltaH degrees indicates that the adsorption process is exothermic. The apparent equilibrium constants (K(a)) are also calculated and found to decrease with increase in temperature.