Amino acid promoted oxidation of atrazine by Fe₃O₄/persulfate

In the present study, we demonstrated that the presence of cysteine could remarkably enhance the degradation of atrazine by Fe₃O₄/persulfate system. The results of electron paramagnetic resonance (EPR) spectra confirmed the combination of cysteine and Fe₃O₄ exhibited much higher activity on activation of persulfate to generate more SO₄^•- and •OH than Fe₃O₄ alone. At pH of 3.0, SO₄^•- and •OH contributed to about 58.2 % and 41.8 % of atrazine removal respectively, while •OH gradually dominated the oxidation of atrazine from neutral condition to alkaline condition. The co-existing Cl^- and HCO₃^- could quench SO₄^•-, resulting in the inhibition of atrazine degradation. The presence of low natural organic matters (NOM) concentration (0-2 mg L^-1) could enhance the atrazine removal, and high concentration (>5 mg L^-1) of NOM restrained the atrazine degradation. During the Cysteine/Fe₃O₄/Persulfate process, cysteine served as a complexing reagent and reductant. Through acidolysis and complexation, Fe₃O₄ could release dissolved and surface bound Fe²⁺, both of which contributed to the activation of persulfate together. Meanwhile, cysteine was not rapidly consumed due to a regeneration process, which was beneficial for maintaining Fe²⁺/Fe³⁺ cycle and constantly accelerating the activation of persulfate for atrazine degradation. The reused Fe₃O₄ and cysteine in the Cysteine/Fe₃O₄/Persulfate process exhibited high stability for the atrazine degradation after three cycles. The degradation pathway of atrazine included alkylic-oxidation, dealkylation, dechlorination-hydroxylation processes. The present study indicates the novel Cysteine/Fe₃O₄/Persulfate process might be a high potential for treatment of organic polluted water.