Fluoride Removal from Aqueous Solutions Using Poly(Styrene Sulfonate)/Nanoalumina Multilayer Thin Films

In the present study, fluoride removal from drinking water is investigated using layer-by-layer (LbL) fabricated poly(sodium 4-styrene-sulfonate) (PSS)/Al₂O₃ thin films. The surface morphology of the fabricated thin films is characterized using atomic force microscopy and field emission-scanning electron microscopy. Optical profilometry is used to determine the self-assembly of the multilayer thin films. The effect of various parameters such as adsorbent dosage, contact time, initial fluoride content, number of bilayers, surface area, and pH is thoroughly studied. Fluoride removal increases with the number of bilayers and number of slides (total surface area). The amount of fluoride adsorbed increases from 11.32 to 26 mg L^-1 when the number of substrates increases from 1 to 5. A 68% removal of fluoride is observed when 20 bilayers of PSS/Al₂O₃ thin films with three slides at an initial fluoride concentration of 5 mg L^-1 are used, thereby bringing down the fluoride concentration level below the World Health Organization permissible limit. Slide reusability studies reveal that the fabricated thin films can be used for ten cycles without affecting the fluoride removal properties of the film. This study demonstrates the potential application of immobilized PSS/Al₂O₃ thin films as an effective adsorbent for drinking water purification.