Kinetics and pathway of atrazine degradation by a novel method: Persulfate coupled with dithionite

Efficient and environmentally friendly activation methods of persulfate (PS)have gained growing attention in the remediation of water or soil polluted by organic contaminants. Among all, the exploration of effective and applicable method for the PS activation becomes one of the hottest topics in the field of organic degradation. Dithionite (DTN)was employed in this study to activate PS and applied to degrade Atrazine (ATZ)without secondary pollution. ATZ could be completely degraded within 90 min by PS/DTN system. ATZ degradation by PS obeyed the pseudo-first-order kinetics and the rate constant values increased from (4.71–5.05)× 10⁻³ min⁻¹ to (4.59–5.09)× 10⁻² min⁻¹ with the addition of DTN. Sulfate radicals were verified to be the dominant reactive species through the radical scavenging experiment. PS/DTN system can remain a strong oxidative ability in the range of pH below 9.0. The presence of Cl⁻, natural organic matter (NOM), and high concentration of HCO₃⁻ may inhibit the removal of ATZ while the low concentration of HCO₃⁻ can slightly promote the degradation. It was found that the degradation pathways of ATZ by PS/DTN involved de-chlorination and hydroxylation, de-alkylation, and de-amination by the reactive species. The study reveals that PS/DTN system has the broad application prospect in the treatment of refractory pollutants.