Abstract: Sulfonamides (SAs) can be degraded effectively by the sulfate radical based advanced oxidation processes (SR-AOPs) in aqueous solutions. The remediation efficiency could be affected by the coexisting heavy metal ions in the natural environment. Accordingly in the present study, we focused on the effects of different metal ions on the activation of persulfate (PS) by goethite for the sulfapyridine (SPY) removal under different pH conditions. The experiments were conducted in systems (initial conditions: goethite, 1.0 g/L; PS, 4 mmol/L; SPY, 10 mg/L; pH=8.2) containing coexisting heavy metal ions (Cu2+, Pb2+ and Cd2+, 0.2 mmol/L) and SPY degradation was monitored. The results showed that the removal of SPY in the goethite/PS system without heavy metal ions was 25.2%, and the effects of Pb2+ and Cd2+ were small (Pb2+, 30.8%; Cd2+, 34.8%). Comparingly, SPY degradation was enhanced to a complete removal (100%) by Cu2+. Mechanistic analysis indicated that Pb2+ and Cd2+ mainly affected the adsorption of SPY in the goethite/PS system, but Cu2+ by itself could activate PS. Under different pH conditions (3.0, 8.0 and 12.0), we confirmed that the Cu2+/goethite/PS system could remove SPY completely from a weak alkaline solution. This study therefore provided experimental evidence in supporting the use of goethite for perfulfate activation in the remediation of complex pollutants in aqueous media.

Key words: goethite, sulfapyridine, heavy metal ion, groundwater, advanced oxidation processes