Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bolonia study programme


1 - 3 / 3
First pagePrevious page1Next pageLast page
Development of Advanced TiO2/SiO2 Photocatalyst for Indoor Air Cleaning
Andraž Šuligoj, 2015, doctoral dissertation

Abstract: TiO2 - SiO2 composites were synthesized by low-temperature sol-gel impregnation method, using four different titania sources (P-25 from Degussa, PC500 from Millennium, CCA 100 AS and CCA 100 BS from Cinkarna, later denoted as AS and BS, respectively) and deposited on aluminium and glass carriers. Ordered and disordered mesoporous silicas were impregnated with ce{TiO2} in powder or suspension form in the Ti : Si molar ratio 1 : 1. Structure, size, band gap, chemical composition and specific surface area of nanoparticles were determined by X-ray diffraction (XRD), scanning (SEM) and transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DR-UV-vis), Fourier transform infrared spectroscopy (FT-IR) and ce{N2} physisorption. Additionally, quantity of surface hydroxyl groups, surface acidity and mechanical stability of the coatings were determined by temperature programmed Fourier transform infrared spectroscopy (TPD-IR) and Wolff-Wilborn method, respectively. The photocatalytic activity of TiO2 and TiO2 - SiO2 composites was evaluated in the photodegradation of toluene and formaldehyde, as model VOCs, under UVA light irradiation in lab-made photoreactor system with two different regimes; batch and plug-flow mode. These two VOCs are being considered as examples of two of the six major classes of indoor air contaminants. Adsorption properties of the samples with toluene, have shown that the addition of mesoporous silica was beneficial. The increase of the adsorption of the bare AS TiO2 (9.5 %) was higher in the case of ordered silica, SBA-15 (2.8 times for AS/SBA15 to 26.8 %) than disordered SiO2 KIL-2 (2.4 times for AS/KIL2 to 22.7 %) although it was significant in both types of mesoporous silica supports (over 20 %). Adsorption was found to be dependent mostly on the quantity of surface Si-OH groups. Regarding the photocatalytic activities towards toluene degradation, the results with pure TiO2 showed the fastest kinetics in case of sample AS followed by PC500 and P25. The observed behaviour was ascribed to smaller particle size, and consequently higher specific surface area. Grafting titania onto silica showed the importance of structural parameters. Most importantly, if the pore structure of bare TiO2 collapsed, this resulted in decreased activity. On the other hand, retainment of the pore structure improved the distribution of nanoparticles, crystallinity and optical properties, which resulted in improved photocatalytic activity. In the degradation of formaldehyde, it was found that adsorption and degradation abilities of the materials were much more dependent on the structural properties of the samples, i.e., the pore structure. This was explained as a consequence of the different degradation mechanisms of both pollutants. Toluene degradation is governed by the oxidation through photogenerated holes - direct oxidation, whereas in the degradation of formaldehyde, the major oxidative species are OH radicals. In addition, the same as in toluene oxidation, the activity was dependent mainly on the number of crystal defects and the band gap values, that is the oxidation and reduction potentials of the catalysts. The degradation efficiency was increased from 88 % in pure AS TiO2 to 97 % when this titania was grafted onto colloidal silica (7C). An important highlight of the thesis is synthesis of a novel photocatalyst, labelled AS7C, which comprises an acidic colloidal suspension AS as TiO2 source and colloidal silica, using a low-temperature sol-gel impregnation method. This sample used all the above mentioned properties that improve photocatalytic activity towards both pollutants. Mechanical stability of the samples was also tested. The tests showed that binder, in the form of colloidal SiO2 (in size of 25 nm) in combination with colloidal titania of appropriate size - 6 nm, produced the highest mechanical stability of the coatings, which also showed excellent photocatalytic activity. Stability of the coatings, using AS as titania source, was greatly improved. The Wolff-Wilborn test on AS coating showed no mechanical resistance, while with the optimal (in terms of photocatalytic performance) addition of 7C SiO2 binder stability was excellent (F, which is in the middle of 6B-6H hardness scale). This sample (AS7C) was also tested for release of aerosols, during operation of the reactor, which could be harmful for human health at longer exposure times. It was found that aerosols are formed, probably as a consequence of detachment of nanoparticles in the first period of photodegradation test. However, their formation in consecutive tests was greatly reduced. Last but not least, a pilot plug-flow reactor was constructed to test the photocatalyst's efficiency in one-pass degradation of toluene. Sample AS7C was able to degrade toluene at conditions applied (v= 400 mL/min, m(catalyst) = 1049 mg, C(0) = 1 ppmv), which means that the out-flow from reactor was clean of the pollutant and any possible intermediates, comprising only of humid air and CO2. Deactivation of the catalyst was found at higher air flow and higher initial concentration of the pollutant. However, the concentrations of pollutants in living conditions are few orders of magnitude lower, hence this is a promising result.
Found in: ključnih besedah
Summary of found: ...Air remediation, TiO2 photocatalysis, Immobilization, Thin layers, TiO2/SiO2 composites...
Keywords: Air remediation, TiO2 photocatalysis, Immobilization, Thin layers, TiO2/SiO2 composites
Published: 31.08.2015; Views: 5592; Downloads: 108
.pdf Fulltext (33,47 MB)

Photocatalytic properties of metal modified TiO2 by photothermal techniques
Mladen Franko, Dorota Korte, Urška Lavrenčič Štangar, Olena Pliekhova, Humberto Cabrera, Zeinab Ebrahimpour, 2018, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ...lens spectrometry, Photothermal beam deflection spectroscopy, Dye remediation, Photothermal technique, Photocatalytic degradation, Reactive Blue 19,...
Keywords: Thermal lens spectrometry, Photothermal beam deflection spectroscopy, Dye remediation, Photothermal technique, Photocatalytic degradation, Reactive Blue 19, TiO2 modification
Published: 09.11.2018; Views: 1389; Downloads: 0
.pdf Fulltext (208,76 KB)

Pollutant removal with organic macrocycle-based covalent organic polymers and frameworks
Ali Trabolsi, Dinesh Shetty, Tina Škorjanc, 2021, review article

Abstract: Air, water, and soil pollution devastate countless ecosystems and deteriorate human health. Adsorption has commonly been used as a pollutant removal technique, but ongoing materials science research is still searching for more efficient, cheaper, and scalable sorbent materials. Herein, we discuss the synthesis and pollutant-capturing abilities of covalent polymeric structures, including covalent organic polymers and covalent organic frameworks that contain organic macrocycles in the backbone of their structures. These organic macrocycles (cyclodextrin, calixarene, cucurbituril, pillararene, and porphyrin) possess cavities and functional groups that can sequester pollutants by forming supramolecular interactions. The insolubility of these materials prominently aids in their regeneration and recyclability potentials. Following a discussion on the synthetic strategies used in the polymerization of each type of macrocycle, environmental applications of these materials are presented. Here, we focus on the removal of micropollutants, charged species, metal ions, oils and organic solvents, perfluorinated substances, iodine, and volatile organic compounds.
Found in: ključnih besedah
Summary of found: ...macrocycles, covalent polymers, covalent organic frameworks, environmental remediation, adsorption...
Keywords: supramolecular interactions, host-guest chemistry, organic macrocycles, covalent polymers, covalent organic frameworks, environmental remediation, adsorption
Published: 09.04.2021; Views: 148; Downloads: 5
URL Fulltext (0,00 KB)
This document has many files! More...

Search done in 0 sec.
Back to top