Hydroxyl and sulfate radical-based oxidation of RhB dye in UV/H2O2 and UV/persulfate systems: Kinetics, mechanisms, and comparison

Xinxin Ding (1) , Leonardo Gutierrez (2) , Jean-Philippe Croué (3) , Minrui Li (1) , Lijun Wang (1) , Yuru Wang (1)

1 SNNU - Shaanxi Normal University
2 UPACIFICO - Universidad Del Pacífico – Ecuador
3 E-BICOM - Eaux, Géochimie organique, Santé [E1 – IC2MP équipe 1]

The degradation kinetics and mechanisms of Rhodamine B (RhB) dye by ^•OH and SO₄^•- based advanced oxidation processes were investigated. The ^•OH and SO₄^•- radicals were generated by UV photolysis of hydrogen peroxide and persulfate (i.e., UV/H₂O₂ and UV/PS), respectively. The effects of initial solution pH, RhB concentration, oxidant dosage, Fe²⁺ concentration, and water matrices were examined. The results showed that the degradation of RhB followed pseudo-first-order kinetics in both processes, with the UV/H₂O₂ process exhibiting better performance than that of the UV/PS process. Acidic conditions were favorable to the degradation of RhB in both systems. Increasing the oxidant dosage or decreasing the contaminant concentration could enhance the degradation of RhB. Photo-Fenton-like processes accelerated the performance when Fe²⁺ was added into both systems. The removal efficiency of RhB was inhibited upon the addition of humic substances. The addition of Cl⁻ displayed no significant effect and promoted RhB degradation in UV/H₂O₂ and UV/PS systems, respectively. The presence of NO₃⁻ promoted RhB degradation, while H₂PO₄⁻ and C₂O₄²⁻ showed an inhibitory effect on both UV/H₂O₂ and UV/PS processes. Radical scavenging tests revealed the dominant role of SO₄^•- radicals in the UV/PS system. Furthermore, the evolution of low molecular weight organic acids and NH₄⁺ during the degradation of RhB in these two processes were compared. Both UV/H₂O₂ and UV/PS systems led to similar formation trends of NH₄⁺ and some ring-opening products (e.g., formic acid, acetic acid, and oxalic acid), suggesting some analogies in the decay pathways of RhB by ^•OH and SO₄^•--induced oxidation processes.

Mots clés: Hydroxyl radical; Sulfate radical; UV/H2O2; UV/PS; Rhodamine B

Domaines: Sciences de l'environnement

Xinxin Ding, Leonardo Gutierrez, Jean-Philippe Croué, Minrui Li, Lijun Wang, et al.. Hydroxyl and sulfate radical-based oxidation of RhB dye in UV/H2O2 and UV/persulfate systems: Kinetics, mechanisms, and comparison. Chemosphere, 2020, 253, pp.126655. ⟨10.1016/j.chemosphere.2020.126655⟩. ⟨hal-03490270⟩