Journal of Food, Agriculture and Environment

Fluoride adsorption on water treatment sludge processed by polyaluminium chloride

Author(s):

Taek-Keun Oh ^*, Jiro Chikushi

Recieved Date: 2009-10-14, Accepted Date: 2009-12-19

Abstract:

Water treatment sludge is an inescapable by-product generated in processing drinking water. The fluoride adsorption potential of PAC (polyaluminium chloride)-processed water treatment sludge obtained from three different locations was investigated in a batch mode as a function of pH, contact time, initial fluoride concentrations and other co-existing anions. The percentage of actual fluoride adsorption for the sludge increased with pH, and the maximum adsorption was observed in a pH range of 5.1 to 6.0, although apparent fluoride adsorption, where metal-fluoride complexes were not counted in acidic solution, showed nearly 100.0% in the pH range of 2.0 to 6.0. Above pH 6.0, fluoride adsorption decreased sharply with pH. Temporal variation of the adsorption showed that it increased abruptly with time in the initial 5 - 60 min, and thereafter smoothly increased until 720 min. In isotherm experiment at pH 5.0, the adsorption increased with equilibrium concentrations of fluoride and the apparent adsorption was higher than the actual adsorption. The adsorption by PAC-processed sludge could be described by the Freundlich isothermal equation because the coefficient of determination (R²) for any sludge samples showed values higher than 0.9 ( P < 0.01). The other anions such as SO₄^2-, NO₃^- and Cl^- did not affect the extent of the apparent adsorption for any sludge samples. From these results we concluded that the PAC-processed water treatment sludge can be reused as an adsorbent for fluoride although slight differences in adsorption characteristics were found among the sludge samples from the three locations.

Keywords:

Fluoride, adsorption, water treatment sludge, reuse, polyaluminium chloride

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Journal: Journal of Food, Agriculture and Environment
Year: 2010
Volume: 8
Issue: 1
Category: Environment
Pages: 358-362

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