Reduction of bromate from drinking water by sulfite/ferric ion systems: Efficacy and mechanisms

摘要

In this work, we investigate radical-based chemical reduction systems for BrO3- reduction. Sulfite/ferric ions [S(IV)/Fe(III)] systems eliminated 85% of 0.1 mM BrO3- in 1 min at pH(ini). 7.0, and 2.2 mg/L dissolved oxygen (DO) with rate constants (2.104 +/- 0.090 min(-1)) orders of magnitude faster than previously published advanced reduction processes. Increasing S(IV) and Fe(III) concentrations and decreasing DO and pH contributed to faster BrO3- reduction likely due to enhanced reactive species. Lower anionic levels (0.5 mM) did not hinder BrO3- reduction but further increases in the levels to 1.0 mM decreased their reduction. Notably, S(IV)/Fe(III) process reduced 68% of 25.6 mu g/L BrO3- in 3 min from tap water at pH(ini). 7.0, 0.02 mM Fe(III), and 1.0 mM S(IV), meeting drinking water standard (10 mu g/L). Also, similar to 99% of irons could be removed after the following activated carbon treatment. Moreover, sulfite radicals formed by S(IV) activation with Fe(III) were significant reactive species in the S(IV)/Fe(III) system. Reduction pathways were proposed accordingly. Collectively, S(IV)/Fe(III) process is a viable technology for reductively decontaminating realistic waters, especially when applied between the ozone-activated carbon process (i.e., the ozone-S(IV)/Fe(III)-activated carbon process).