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Enhancement of Limestone Defluoridation of Water by Acetic and Citric Acids in Fixed Bed Reactor
Author(s) -
Nath Suresh K.,
Dutta Robin K.
Publication year - 2010
Publication title -
clean – soil, air, water
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 66
eISSN - 1863-0669
pISSN - 1863-0650
DOI - 10.1002/clen.200900209
Subject(s) - fluoride , distilled water , chemistry , acetic acid , dissolution , citric acid , sulfate , nuclear chemistry , precipitation , chloride , phosphate , adsorption , nitrate , bromide , inorganic chemistry , chromatography , organic chemistry , physics , meteorology
Limestone defluoridation by fixed bed reactor has been studied with water pre‐acidified with edible organic acids, viz. acetic acid (AA) and citric acid (CA). The study has been carried out by varying acid concentration, contact time ( t ), number of repeated use of the same limestone bed ( n ), and chip size of the crushed limestone using fixed fluoride concentration of 10 mg/L in distilled water and groundwater amended to that concentration of fluoride. The presence of both the acids considerably improved the fluoride removal and the removal increased with increase in the acid concentration. Fluoride removal to less than 0.5 and 1.0 mg/L from initial 5 and 10 mg/L, respectively, have been achieved by the method on treatment with single reactor. The mechanism of fluoride removal in the process thought to be the increase in Ca 2+ activity by dissolution of limestone, which precipitates as CaF 2 . XPS analysis reveals that adsorption also contribute to the fluoride removal along with precipitation. The final pH of water remained within acceptable range for drinking water. Initial concentration of fluoride, effects the removal ability of the limestone particles only to some extent. The influence of other anions on fluoride removal process has a little influence which follows the order phosphate > sulfate > bromide > chloride > nitrate.