Boron adsorption on alumina (Al2O3) and magnesia (MgO) in aqueous solutions: a comparative study
The adsorption of boron on alumina (Al2O3) and magnesia (MgO) has been investigated in aqueous solutions as a function of pH, boron concentration, amount of adsorbent, ionic strength and temperature. Analysis of the experimental data indicates that under the optimum pH conditions, the adsorption mechanism depends on the nature of the oxide. Boron adsorption on alumina is based on the replacement of a water molecule by a boric acid molecule. In contrast, boron adsorption on magnesia is based on electrostatic attraction between the positively charged surface of the oxide and the borate anions. The existence of two different adsorption mechanisms is supported by the ionic strength effect on the two different adsorption processes and their thermodynamic parameters. Data obtained from corresponding adsorption experiments performed with natural waters of different chemical composition agree with data obtained from laboratory systems.
Keywords: boron adsorption, alumina, magnesia, adsorption isotherms, thermodynamic data, removal efficiency, natural waters, wastewater treatment, water treatment, irrigation