Adsorption of fluoride by the calcium alginate embedded with Mg-Al-Ce trimetal oxides

摘要

Batch experiments were conducted to study the adsorption performance of fluorine removal by the calcium alginate (SA) embedded by the composite Mg-Al-Ce oxides (SA-CMAC). The physical and chemical properties of the SA-CMAC were characterized by XRD, SEM and XPS analysis. The optimum conditions for fluoride removal were determined and the maximum adsorption capacity was 26.12mg g_(−1). The co-existing PO ~(4)_(3−) and CO ~(3)_(2−) anions in solution had more effect than the SO ~(4)_(2−) and NO ~(3)_(-) on the fluoride removal efficiency. The adsorption process of fluorine by SA-CMAC was attributed to ion exchange on the surface of the SA-CMAC. The experimental data fitted both the isotherms and Freundlich well, and the Freundlich model had a little higher correlation coefficient. As the rate determining step, the adsorption process could be best described by the pseudo-second order kinetic model followed by the intra-particle diffusion. The thermodynamic examination demonstrated that the fluoride adsorption on the SA-CMAC beads was reasonably spontaneous and exothermic. The reclaimed adsorbents still could adsorb 65% of the total fluoride in the solution after three cyclic processes using 0.01mol/L NaOH.