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 center dot- and center dot OH than Fe3O4 alone. At pH of 3.0, SO4 center dot- and center dot OH contributed to about 58.2 % and 41.8 % of atrazine removal respectively, while center dot OH gradually dominated the oxidation of atrazine from neutral condition to alkaline condition. The co-existing Cl- and HCO3- could quench SO4 center dot-, 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.