Ferrous ion-tartaric acid chelation promoted calcium peroxide fenton-like reactions for simulated organic wastewater treatment

To overcome the handicaps limiting the performance of conventional Fenton processes for effluent treatment, an improved Fenton process based on substituting the hydrogen peroxide (H2O2) with calcium peroxide (CaO2) and adding tartaric acid (TA) as the chelating agent for Fe2+ was proposed. The results indicated that methylene blue (MB) and sulfamethoxazole (SMX) could be effectively degraded by the CaO2/Fe2+/TA synergistic system. With the optimal CaO2/Fe2+/TA ratio (1:0.5:1 mmol L−1), MB and SMX removals reached 94.82% and 99.61% after 300 and 600 s of reaction, respectively. The UV–vis spectra and iron analyses demonstrated that TA increased the conversion of Fe3+ to Fe2+ and decreased iron sludge production. Fe2+-TA complexation improved H2O2 decomposition. The radical scavenging activity and electron paramagnetic resonance studies confirmed the formations and roles of hydroxyl (·OH), singlet oxygen, and superoxide radicals, and the pollutant removal was primarily due to the ·OH-driven reactions. The decomposition mechanisms for MB and SMX were proposed based on the obtained mass spectra. The ecotoxicity of the SMX primary byproducts was predicted using a toxicity estimation software tool.