Degradation of Carbamazepine by Photo(electro)catalysis on Nanostructured TiO2 Meshes: Transformation Products and Reaction Pathways

Abstract

Carbamazepine (CBZ) is a pharmaceutical compound recalcitrant to conventional wastewater treatment plants and widely detected in wastewater bodies. In the present study, advanced oxidation processes for carbamazepine removal are investigated, with particular regard to the degradation pathways of carbamazepine by photoelectrocatalysis and conventional photocatalysis. Photoelectrocatalysis was carried out onto TiO2 meshes obtained by Plasma Electrolytic Oxidation, a well-known technique in the field of industrial surface treatments, in view of an easy scale-up of the process. By photoelectrocatalysis, 99% of carbamazepine was removed in 55 min while only 65% removal was achieved by photolysis. The investigation of the transformation products (TPs) was carried out by means of UPLC-QTOF/MS/MS. Several new TPs were identified and accordingly reaction pathways were proposed. Above 80 min the transformation products disappear, probably forming organic acids of low-molecular weight as final degradation products. The results demonstrated that photoelectrocatalysis onto TiO2 meshes obtained by plasma electrolytic oxidation is a useful alternative to common advanced oxidation processes as wastewater tertiary treatment aimed at removing compounds of emerging concern.

Single‐Step Preparation of Large Area TiO2 Photoelectrodes for Water Splitting

“…Owing to its nontoxicity, low cost, good chemical stability, and band energy levels suitable for excitation under UV–vis irradiation, titanium dioxide and its doped variants are considered among the most viable electrode materials for photocatalytic applications, such as water and air depollution, water splitting and CO 2 reduction. [ 1–8 ] Out of all techniques for the growth of thin films for photoelectrodes preparation, [ 9–11 ] Plasma Electrolytic Oxidation (PEO) allows to easily synthesize photoactive TiO 2 layers with tuned crystalline phase composition [ 12–14 ] and dosage of doping elements. [ 15–21 ]…”

Photocatalytic degradation of oily waste and phenol from a local South Africa oil refinery wastewater using response methodology

“…AOP in recent times is gaining attention for mineralization of ORW because it offers distinct merits over many conventional treatments 31 . In comparison, AOP has the potential to destroy a wide range of organic and recalcitrant pollutants to completion within a shorter possible time than biological systems [32][33][34] .…”

“…Classifying types of AOPs are generally based on the techniques used in generating the reactive radicals and the relative oxidation potential (estimated to be +2.8 V). Some of the oxidants like ozone, H 2 O 2 , HOCl, and chlorine have high oxidation potentials as 2.07 V, 1.78 V, 1.49 V, and 1.36 V respectively [31][32][33][34][35][36] . The single-use or combination of any of these oxidants exposed to ultraviolet (UV) or sunlight radiation produces oxidative species (OH − , O 2− ) 36,37 .…”

“…In all the cited scenarios, the generation of OH radicals is very essential for the photocatalysis process due to their high reactivity [39][40][41] . Among them, titanium dioxide (TiO 2 ), has been the most effective photocatalyst or semiconductor for wastewater applications 31 .…”

“…Heterogeneous photocatalytic oxidation (HPO) that utilizes TiO 2 , when exposed to UV light is said to produce the most powerful intermediary oxidative radicals. HPO is seen as a promising route for degrading recalcitrant organic pollutants with less toxic substances [31][32][33][34] . As most promising technologies are associated with complex operating parameters that can affect their performance, HPO cannot be left out 37,41,42 .…”