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Boron recovery from high boron containing wastewater using modified sub-micron Ca(OH)2 particle
Tsai, H.C. & Lo, S.L.
Abstract
In the present study, two modified calcium
hydroxide (Ca(OH)2) particles, sub-micron Ca(OH)2 made
by CaCl2 and Ca(NO3)2, were applied to improve efficiency
of boron recovery from concentrated wastewater
under mild temperature conditions. The two modified calcium
hydroxide particles led to higher recovery efficiencies
at 95 °C for 1 h (77.2 and 76.3 %) as compared to the
efficiency by using un-modified Ca(OH)2 (67.2 %). The
difference was due to their different particle size constitutions.
For the reaction kinetic of boron removal, it was
found that the pseudo-first-order model fitted well in the
experimental data. The sub-micron Ca(OH)2 were used to
remove and recover boron from a polarizer manufacturing
wastewater. The findings revealed that it is worth recovering
the boron containing precipitates because of the close
boron content in the precipitates (sub-micron Ca(OH)2
made by CaCl2: 7.0 %, sub-micron Ca(OH)2 made by
Ca(NO3)2: 7.1 %) as compared to natural boron minerals
(borax: 11.3 %). In addition, in order to estimate energy
efficiency of boron recovery by chemical precipitation
method, an evaluating formula, energy consumption of
boron uptake, was developed. The value of energy consumption
of boron uptake by using sub-micron Ca(OH)2
made by CaCl2 with the optimum condition was
comparatively high (35.4 μg-B/g-Ca(OH)2/kJ). Therefore,
the sub-micron Ca(OH)2 particles were observed more
effective for boron recovery from concentrated wastewater
under moderate temperatures.
Keywords
Sub-micron particle; Chemical precipitation; Boron removal; Boron recovery; Polarizer manufacturing wastewater
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