Titanate nanotube-based catalysts were prepared via alkaline hydrothermal synthesis route followed by heat-treatment at different temperatures, ranging from 300 to 700 °C. The resulting metal-free solids were then applied as a catalyst in a three-phase trickle-bed reactor, where catalytic wet air oxidation (CWAO) reactions of model aqueous Bisphenol A (BPA) solution were performed. It was observed in the given range of operating conditions that BPA undergoes both non-catalytic as well as catalytic oxidation routes, while the latter is far more pronounced. At 210 °C and in the presence of 0.5 g of titanate nanotube-based catalyst, which was annealed at 600 °C, a complete BPA removal was obtained. From TOC point of view, approximately 70% conversion was achieved indicating the persistence of refractory intermediates of lower carboxylic acids.
COBISS.SI-ID: 5149722
Catalytic wet air oxidation (CWAO) of aqueous bisphenol A (BPA) solution was studied in a continuous-flow trickle-bed reactor in the presence of titanate nanotube-based catalysts. These active metal-free solids were prepared by alkaline hydrothermal synthesis followed by heat treatment at temperatures ranging from 300 to 700 °C, so that they would have varying physicochemical properties. The aim of the study was to investigate the removal efficiency of titanate nanotube-based catalysts used in the CWAO process to remove toxicity and estrogenicity of BPA at a very short space time of 0.6 min•gCAT•g−1. In addition, noncatalytic BPA degradation in the presence of inert SiC particles was also performed. As a result, significantly higher estrogenicity and toxic effects of the liquid-phase sample compared to the catalytic oxidation experiments were observed. Complete removal of estrogenicity and high reduction of toxicity from aqueous solution were achieved at 210 °C over 0.5 g of catalyst that had been annealed at 600 °C.
COBISS.SI-ID: 5312282
Model aqueous solution of bisphenol A (BPA) of 10 mg L–1 was treated in a continuous and sequential catalytic wet air oxidation (CWAO)/aerobic bioreactor (BR) system. Wet oxidation with titanate nanotube-based catalyst resulted in nearly complete removal of BPA () 99 %) at a very short space time of 0.3 min•gCAT•g–1. The main identified oxidation products in the CWAO effluent were acetic acid, formic acid and p-hydroxyacetophenone (p-HAP). All of these compounds were consequently and efficiently removed in the BR system at a hydraulic residence time (HRT) of 7.2 h. Although apparent toxicity of the CWAO effluent was found higher than of the initial BPA solution, the former could be successfully detoxified through aerobic biodegradation. The combined system thus presents a potential treatment process for the efficient removal of BPA and its oxidative derivatives from wastewaters.
COBISS.SI-ID: 5262106
Titanate nanotubes (TNTs) were prepared via alkaline hydrothermal synthesis route followed by acid washing at ambient conditions. The resulting high specific surface area nanotubular solids were further modified by two distinguished post-treatments: (i) heat-treatment in the temperature range from 300 to 700 °C, and (ii) peroxide-treatment at room temperature. Bisphenol A (BPA), a well-known endocrine disrupting compound (EDC), was selected as a testing molecule to evaluate the photodegradation potency of the modified TNTs. The resulting BPA and TOC removals confirmed that crystallinity and BET surface area of examined heat-treated solids play a crucial role in governing the photooxidation reaction. Regarding the peroxide-treated TNTs, a nearly three-fold improvement in BPA removal was attained in comparison to the pristine TNTs, which can be attributed to the redox reaction of surface titanium(IV) peroxo groups. However, the exposure of anatase-based samples to the H2O2 medium resulted in deteriorated photocatalytic oxidation of the model compound, due to recovery of surface Ti3+ defect sites, leading to increased e−–h+ recombination and decreased oxygen adsorption.
COBISS.SI-ID: 5480986
Catalytic wet air oxidation (CWAO) is classified as an advanced oxidation process, which proved to be highly efficient for the removal of emerging organic pollutant bisphenol A (BPA) from water. In this study, BPA was successfully removed in a batch-recycle trickle-bed reactor over bare titanate nanotube-based catalysts at very short space time of 0.6 min gCAT g−1. The as-prepared titanate nanotubes, which underwent heat treatment at 600 °C, showed high activity for the removal of aqueous BPA. Liquid-phase recycling (5- or 10-fold recycle) enabled complete BPA conversion already at 200 °C, together with high conversion of total organic carbon (TOC), i.e., 73 and 98 %, respectively. The catalyst was chemically stable in the given range of operating conditions for 189 h on stream.
COBISS.SI-ID: 5490202