Kinetic modelling of TOC removal in the photocatalytic ozonation of diclofenac aqueous solutions

Photocatalytic ozonation (O3/UV/TiO2) is an emerging oxidation method for recalcitrant organic contaminants in water. However, immobilised TiO2 catalysts suffer from reduced photonic efficiency. Therefore, TiO2 catalysts with excellent mechanical and thermal properties and enhanced photonic efficiencies are sought. This paper aimed to elucidate the mineralisation of low concentration 2,4-D (45.0 μM) by O3/UV/TiO2 using the world's first high-strength TiO2 fibre in laboratory batch experiments. 2,4-D degradation and TOC removal followed pseudo first-order reaction kinetic. The removal rates for 2,4-D and TOC in O3/UV/TiO2 were 1.5 and 2.4-fold larger than the summation of the values for ozonation (O3) and photocatalysis (UV/TiO2), respectively. O3/UV/TiO2 was characterised by few aromatic intermediates with low abundance, fast degradations of aliphatic intermediates and dechlorination as a major step. The significantly enhanced 2,4-D mineralisation in O3/UV/TiO2 was attributed to increased ozone dissolution and decomposition, and reduced electron–hole recombination resulting in large number of hydroxyl radical (•OH) formation from more than one parallel path. The discrepancies in the organic carbon mass budget were attributed to few apparently major unidentified intermediates, while chlorine mass balance was reasonably acceptable. The mineralisation efficiency of O3/UV/TiO2 with the TiO2 fibre can further be enhanced by optimisation of experimental design parameters. The new TiO2 fibre is very promising to overcome the problem of reduced efficiency of TiO2 catalyst in an immobilised state.

Download Full-text

Kinetic modelling of colour changes in aqueous solutions of phenol oxidized by sono-Fenton technology

10.5004/dwt.2018.22469 ◽

2018 ◽

Vol 127 ◽

pp. 32-40 ◽

Cited By ~ 1

Author(s):

N. Villota ◽

◽

J.M. Lomas ◽

A. Santaolalla ◽

L.M. Camarero

Keyword(s):

Aqueous Solutions ◽

Kinetic Modelling ◽

Colour Changes

Download Full-text

Ozone-Based Advanced Oxidation Processes for Primidone Removal in Water using Simulated Solar Radiation and TiO2 or WO3 as Photocatalyst

Molecules ◽

10.3390/molecules24091728 ◽

2019 ◽

Vol 24 (9) ◽

pp. 1728 ◽

Cited By ~ 6

Author(s):

Manuel A. Figueredo ◽

Eva M. Rodríguez ◽

Manuel Checa ◽

Fernando J. Beltran

Keyword(s):

Transformation Products ◽

Degradation Pathway ◽

Secondary Effluent ◽

Ultrapure Water ◽

Visible Radiation ◽

Beneficial Effects ◽

Photocatalytic Ozonation ◽

Toc Removal ◽

Water Matrix ◽

Environmentally Safe

In this work, primidone, a high persistent pharmacological drug typically found in urban wastewaters, was degraded by different ozone combined AOPs using TiO2 P25 and commercial WO3 as photocatalyst. The comparison of processes, kinetics, nature of transformation products, and ecotoxicity of treated water samples, as well as the influence of the water matrix (ultrapure water or a secondary effluent), is presented and discussed. In presence of ozone, primidone is rapidly eliminated, with hydroxyl radicals being the main species involved. TiO2 was the most active catalyst regardless of the water matrix and the type of solar (global or visible) radiation applied. The synergy between ozone and photocatalysis (photocatalytic ozonation) for TOC removal was more evident at low O3 doses. In spite of having a lower band gap than TiO2 P25, WO3 did not bring any beneficial effects compared to TiO2 P25 regarding PRM and TOC removal. Based on the transformation products identified during ozonation and photocatalytic ozonation of primidone (hydroxyprimidone, phenyl-ethyl-malonamide, and 5-ethyldihydropirimidine-4,6(1H,5H)-dione), a degradation pathway is proposed. The application of the different processes resulted in an environmentally safe effluent for Daphnia magna.

Download Full-text