Journal of Water Supply: Research and Technology—AQUA Vol 55 No 6 pp 413–418 © IWA Publishing 2006 doi:10.2166/aqua.2006.026
Adsorption behaviour of calcined layered double hydroxides towards removal of fluoride from aqueous solution
Liang Lv
The West Branch of Zhejiang University of Technology, Zhejiang, 324006, China Tel.: +86 570 8510552 Fax: +86 570 8026668lianglv_qzxy@126.com
ABSTRACT
Removal of fluoride from aqueous solution by calcined layered double hydroxides (CLDHs) was investigated in batch mode. The influences of calcined temperature, Mg/Al molar ratio of CLDHs, pH of aqueous solution, temperature and co-existing anions on the removal of fluoride have been discussed in detail. It was found that the LDHs with an Mg/Al ratio of 2 calcined at 500°C had the highest capacity to remove fluoride and the maximum percentage removal of fluoride takes place at pH 6.0. The adsorption capacity of CLDHs decreases with a rise in temperature, indicating that the removal process is exothermic in nature. The data from isotherms fitted well to the linearly transformed Langmuir equation. The negative values of DG0 and DHo calculated using the Langmuir constant, confirm the spontaneous and exothermic nature of the removal of fluoride.
Keywords: adsorption, calcined, defluorination; fluoride; layered double hydroxides; removal
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