Investigating the chemistry of alumina based defluoridation using safe H+ source
Publication date: 22 November 2018
Source: International Journal of Hydrogen Energy, Volume 43, Issue 47
Author(s): Akshay R. Bavda, Pratap S. Bapat, Vishal B. Joshi, Rajendra S. Thakur
The existence of high levels of fluoride in drinking water is a worldwide problem and activated alumina is an established adsorbent for fluoride removal. This article investigates factors governing rate of fluoride uptake, mechanical stirring as well as interference from competing ions, of the defluoridation employing activated alumina. Pre-treatment with aqueous solution of sulphuric acid has shown faster uptake in a small setup was demonstrated recently. An attempt to understand the phenomena by profiling ionic species on the active surface of activated alumina, native and acid treated. Presence of carbonate species was found, in Raman spectra, on native surface which can explain effectiveness of pre-treatment. Broadening of hydroxyl species profiles, in infrared and solid-state NMR spectra, suggests incorporation of water into new sites. Fluoride treatment of the pre-treated activated alumina leads to narrowing of hydroxyl species profiles suggesting incorporation of fluoride into new sites. A mechanism is being proposed wherein H+ ions in the presence of SO42- (from KHSO4 or NaHSO4) enables the energetics for faster defluoridation and regeneration of activated alumina.