Appraisal of Fluoride Removal Capability of Al-Fe Oxide-Infused Diatomaceous Earth in a Continuous-Flow Fixed-Bed Column

This study was carried out to appraise the groundwater fluoride removal effectiveness of Al-Fe oxide-infused diatomaceous earth (DE) in a continuous-flow fixed-bed column. The adsorbent was optimally synthesized and then characterized. A glass column designed for the experiment was packed with the test adsorbent at specific doses. The effects of flow rate, influent fluoride concentration and bed height (adsorbent dose) on fluoride removal were evaluated by fixing the value of a parameter while varying the others. The breakthrough volume was the volume of treated water obtained until the concentration of fluoride in the treated water reached 1.5 mg/L, which is the World Health Organization’s maximum limit of fluoride in drinking water. The maximum breakthrough volume obtained in this study was 118.2 mL under the optimum conditions of influent F− concentration = 5 mg/L, 1 g of adsorbent with an initial bed height = 7.5 cm and a flow rate = 1.97 mL/min. Channeling and the presence of PO43− as a co-existing anion were limiting factors for the attainment of the breakthrough volume for groundwater defluoridation. Further work is encouraged to investigate a suitable binder that can hold the adsorbent particles firmly together, is not water-soluble, but remains water-permeable when dry. The resulting solid mass could then be pulverized into granules whose weight and rigidity would make them less susceptible to the channeling effect in the column.