Removal of sulfapyridine by ferrate(VI): efficiency, influencing factors and oxidation pathway.

The removal of sulfapyridine (SPY) by ferrate(VI) in aqueous solutions under a broad range of reaction conditions, including ferrate(VI) dosage, solution pH, natural organic matter and coexisting inorganic ions, was systematically investigated and the oxidation pathway of SPY by ferrate(VI) was deeply explored. Results showed that 500 µg/L of SPY was efficiently decomposed (86%) within 1 min by 5 mg/L ferrate(VI) at pH 5.6. The increment in ferrate(VI) dosage was surely favorable for SPY removal. The best SPY degradation was achieved at pH 5.6, under or above which the removal decreased. The introduction of inorganic ions in solutions retarded SPY removal. Ten oxidation intermediates were identified and the cleavages of C-S and S-N bonds might be the primary ways of SPY oxidation by ferrate(VI).