Adsorption of MoO₄^2- ions on Fe-treated tri-calcium phosphate

Abstract

The Fe-treated calcium phosphate (Fe-TPO₄) has been prepared with FeCl₃ aqueous solution. The sorption of ⁹⁹MoO₄^2- ions from aqueous solution using Fe-TPO₄ as adsorbent is investigated by batch experiments. Experiments have been performed as a function of shaking time, <i style="">p</i>H, solute concentration and temperature and the experimental rate data are tested with the pseudo-second-order rate model. The adsorption data as a function of molybdate concentration obey the Freundlich isotherm. Thermodynamic parameters <img src='/image/spc_char/delta.gif' border=0><i style="">H</i>⁰, <img src='/image/spc_char/delta.gif' border=0><i style="">S</i>⁰ and <img src='/image/spc_char/delta.gif' border=0><i style="">G</i>⁰ have been calculated with data of temperature studies. The positive value of <img src='/image/spc_char/delta.gif' border=0><i style="">H</i>⁰ indicates that the adsorption of MoO₄^2- ions on Fe-TPO₄ is an endothermic process.