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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.
Endemic fluorosis affects millions of people worldwide. Fluorosis arises from the consumption of fluorine (F) contaminated water and was observed also in some parts of Turkey with volcanic rocks and geothermal resources. In the present study the removal of F from drinking water by raw and modified bauxite at the laboratory scale was investigated using a batch mode. Modified bauxite was prepared by using Na and Mg incorporated (B-Na, B-Mg) bauxite and calcination of Mg incorporated bauxite at 500°C (B-Mg-500). The equilibration time for F between bauxite and water was identified to be 3 h. Adsorption of F increased with increasing adsorbent dose. Moreover, F adsorption isotherms fitted well with the Freundlich model. Low F adsorption was obtained onto the raw and incorporated bauxite. In contrast, maximum F adsorption was found for B-Mg-500, with Kf value of 0.247. This observation may be explained by the meaningfully stabilized and elevated number of positively charged sites in B-Mg-500.
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