The sequestral capture of fluoride, nitrate and phosphate by metal-doped and surfactant-modified hybrid clay materials

Toxic anions removal for increased access to potable water remains a problem that has not been adequately addressed. This study, reports the successful preparation and modification of kaolinite-papaya seed based adsorbents under vacuum (VHYCA) for the removal of Nitrate (NO3 (-)), Fluoride (F-) and Phosphate (PO4 (3-)). Modified adsorbents via metal-doping using Zinc were more efficient in removing these anions from aqueous solution compared with surfactant-modified adsorbents. However, both type of adsorbents showed a higher preference for NO3 (-) removal with Zn-VHYCA and Fe-VHYCA adsorbents having 98 and 85% removal of the anion from aqueous solution, respectively. The removal of F- and PO4 (3-) was best achieved by Ortho-phenylenediamine (OP) and N,N,N',N'-Tetramethyl-1,4-phenyldiaminedihydrochloride (TPD) modified VHYCA, respectively. However, Zn-VHYCA adsorbent showed comparable results with TPD-VHYCA in the removal of PO4 (3-) from aqueous solution. Overall, the metal-doped hybrid clay adsorbents showed better efficiency for the removal of anions than the surfactant-modified hybrid clay adsorbents.