The photocatalytic oxidation of dibenzothiophene (DBT)

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 2008-10, Vol.294 (1), p.74-81
• Main Authors: Vargas, Ronald, Núñez, Oswaldo
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; DBT 5,5-dioxide (DBT sulfone); Dibenzothiophene (DBT) degradation–mineralization; Exact sciences and technology; General and physical chemistry; Langmuir–Hinshelwood; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; TiO 2–UV solar light; Triton X-100
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2008.08.001

DBT is solubilized into Triton X-100 micelles from where it exchanges with water and becomes ready for degradation. At Triton X-100 at [Triton X-100] > CMC (critical micelle concentration), DBT is readily degraded without degrading Triton X-100 at t 1/2 ca. 120 min. Triton X-100 monomers only slightly compete with DBT for the TiO 2 catalytic site. ▪ TiO 2/UV solar light degradation of dibenzothiophene (DBT) aqueous solutions readily occurs in neutral and acid media. For instance, at neutral pH, t 1/2 = 30 min are found for DBT degradation and mineralization. In neutral and acid media the rate limiting step for mineralization is the same as for degradation and corresponds to the DBT sulfone formation. Benzaldehyde is the major reaction product. In addition, it also acts as an intermediate in the mineralization to CO 2 + water + sulfate. The results support the Langmuir–Hinshelwood degradation mechanism. Therefore, instead of pseudo-first-order rate constants, apparent rate constants that depend on concentration are obtained. Only at basic pH these apparent rate constant are independent of the [DBT] 0. The solubility of DBT in water is increased by one-order of magnitude when solutions of the surfactant Triton X-100 is used at [Triton X-100] > CMC (critical micelle concentration). Under these conditions DBT is readily degraded without degrading Triton X-100 at t 1/2 ca. 120 min. DBT is solubilized into Triton X-100 micelles from where it exchanges with water and becomes available for degradation. Triton X-100 monomers slightly compete with DBT for the TiO 2 catalytic site. The degradation method established in this work might be used, for instance, to decontaminate soil contaminated with sulphur-rich heavy oil following a pre-treatment consisting of washing out the solid with Triton X-100 solutions, prior to photolysis.