Rejection of Bromide and Bromate Ions by a Ceramic Membrane.

Effects of pH and the addition of calcium chloride (CaCl(2)) on bromate (BrO(3) (-)) and bromide (Br(-)) rejection by a ceramic membrane were investigated. Rejection of both ions increased with pH. At pH 8, the rejection of BrO(3) (-) and Br(-) was 68% and 63%, respectively. Donnan exclusion appears to play an important role in determining rejection of BrO(3) (-) and Br(-). In the presence of CaCl(2), rejection of BrO(3) (-) and Br(-) ions was greatly reduced, confirming the importance of electrostatic interactions in determining rejection of BrO(3) (-) and Br(-). The effect of Ca(2+) is so pronounced that in most natural waters, rejection of both BrO(3) (-) and Br(-) by the membrane would be extremely small.