Removal of fluoride ions from aqueous solution at low pH using schwertmannite

Akbar Eskandarpour, Maurice S. Onyango, Aoyi Ochieng, Shigeo Asai

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157 Citations (Scopus)


Wastewater containing fluoride requires polishing after precipitation/coagulation treatment in order to meet stringent environmental legislation. Accordingly, adsorption characteristics of fluoride onto schwertmannite adsorbent were studied in a batch system with respect to changes in initial concentration of fluoride, equilibrium pH of sample solution, adsorbent dosage and co-existing ions. Equilibrium adsorption data were obtained at 295.6, 303 and 313K, and are interpreted in terms of two-site Langmuir, Freundlich, Langmuir–Freundlich, Redlich–Peterson, Tóth and Dubinin–Radushkevitch isotherm models. The experimental and equilibrium modeling results revealed that the capacity of schwertmannite for fluoride is high but insensitive to changes in solution temperature. An increase in equilibrium pH of sample solution reduced significantly the fluoride removal efficiency. In binary component systems, inner-sphere complex forming species had negative effects on fluoride adsorption while outer-sphere complex forming species improved slightly the fluoride removal efficiency. The schwertmannite adsorbent was regenerable and had the ability to lower the fluoride concentration to acceptable levels.
Original languageEnglish
Pages (from-to)571-579
Number of pages9
JournalJournal of Hazardous Materials
Issue number2
Publication statusPublished - 2008


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