Aqueous degradation of artificial sweeteners saccharin and neotame by metal organic framework material

The artificial sweeteners (ASs) saccharin (SAC) and neotame (NEO) are widely used across the globe and are considered as emerging contaminants in surface, ground, and drinking waters. To degrade SAC and NEO, the metal organic framework material Co-based bio-MOF-11 was prepared by hydrothermal reaction and used with peroxymonosulfate (PMS) activator. The effects of the initial concentration of SAC and NEO, bio-MOF-11-Co dosage, PMS concentration, initial pH, temperature, and competitive anions were determined. The results revealed that bio-MOF-11-Co effectively catalyzed the degradation of SAC and NEO and possessed good stability and recycling efficiency. The degradation reaction was effective from pH 3.6–9.8 and followed quasi-first-order kinetics with degradation rate constants of 0.001–0.013 min−1 for SAC and 0.03–0.52 min−1 for NEO. Increased temperature was conducive to the degradation of both artificial sweeteners. The presence of Cl− inhibited the degradation of SAC and NEO, while the presence of CO32− promoted their degradation. Electron paramagnetic resonance (EPR) and free radical quenching demonstrated that the primary free radicals were sulfate radicals (SO4−·) and hydroxyl radicals (HO). The change of cobalt oxidation state and electron transfer in bio-MOF-11-Co mainly induces the production of SO4−·. A plausible mechanism for degradation is SO4−· and HO attack on CS bonds, NS bonds, and benzene rings.