Bromate removal by gamma irradiation in aqueous solutions

Bromate (BrO3-) is a disinfection by-product in drinking water, and its removal is very difficult especially at low levels. Co-60 gamma rays were used to remove BrO3- in aqueous solution in this study. The effects of absorbed doses, BrO3- initial concentration, gas saturation, pH value and coexisting anions (Cl-, NO3-, SO42- and HCO3-/CO32-) on BrO3- reduction were evaluated. After 4.0-kGy irradiation of air-equilibrated solution of 30.7 mu g/L BrO3-, the residual BrO3- was 8.3 mu g/L, which is below the maximum contaminant level of drinking water. The BrO3- reduction rate increased with the dose, in the order of N-2 > air > O-2 > N2O atmosphere under similar conditions. The results also show that high pH favored the BrO3- removal. According to the experimental results, it can be concluded that the efficiency of decomposing BrO3- by reactive species followed the order of center dot e(aq)(-) > center dot H > HO2 center dot > O-2(-)center dot. Coexisting Cl-, HCO3-/CO32- and SO42- ions have little effect on BrO3- removal, whereas NO3- can inhibit its removal as a result of competition with BrO3- for center dot e(aq)(-).