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Thole, B., Mtalo, F.W. and Masamba, W.R.L., 2011. Water defluoridation with 150–300oC calcined Bauxite-Gypsum-Magnesite (BG-Mc) filters. Water Resources Management VI, 145, p.383. |
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Research on water defluoridation with composite filters of bauxite, gypsum and
magnesite was carried out at Ngurdoto Research Station to determine capacity,
nature of fluoride-sorbent interaction and changes in water quality. The objective
was to identify an optimum composite filter that would not alter the water quality
beyond World Health Organisation recommendations. The three materials were
characterized through X-Ray Fluorescence. The major components were Al2O3
(30.33%) for bauxite, CaO (28.09%) for gypsum and MgO (34.57%) for
magnesite. The materials were calcined at temperatures of 150, 200, 250 and
300o
C. Six composite filters were prepared for each calcine temperature of
bauxite:gypsum:magnesite in the ratios 1:2:3, 1:3:2, 2:1:3, 2:3:1, 3:1:2 and 3:2:1.
The highest capacity, 11.77 mg F/g, was obtained with the 3:1:2–200o
C calcine.
The optimum filter was however the 1:2:3–200o
C calcine with capacity of
10.19 mg F/g. This filter did not alter the water quality beyond the considered
WHO limits. The fluoride-sorbent interaction could best be described by
Langmuir isotherm for the 200 and 300o
C, and Temkin isotherm for the 150 and
250o
C composites. Most composites changed water quality beyond WHO
standards in Al3+, Fe2+, and 2 SO4 , however a composite filter of these materials is
plausible. |
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