Adsorption of Fluoride on the Raw and Modified Cement Clay

Abstract

Adsorption of fluoride (F) on the raw and modified local cement clay was investigated by batch method. Modified clays were prepared through calcination, using the Na and Mg saturated (C-Na, C-Mg) clay at 500 and 850°C (C-500, C-850) and calcination of Mg incorporated clay at 500°C (C-Mg-500). The equilibration time was attained in 5 h. Adsorption of F increased with increasing adsorbent dose. Decrease of the initial F concentration resulted in an increasing amount of F adsorption. F adsorption isotherms fitted well with both Freundlich and Langmuir models. Low F adsorption was obtained on the raw, incorporated or calcined clays. However maximum F adsorption was found for C-Mg-500, with Kf and Q0 values of 0.27 and 1.69, respectively. This work indicated that the calcination of incorporated clay with Mg increased the F adsorption significantly, due to increased and stabilized positive sites.