Photocatalytic water treatment with different TiO2 nanoparticles and hydrophilic/hydrophobic layer silicate adsorbents (original) (raw)
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TiO 2 -Based Photocatalytic Degradation of 2-Chlorophenol Adsorbed on Hydrophobic Clay
Environmental Science & Technology, 2002
The combination of adsorption and heterogeneous photocatalysis has been investigated as a promising technology for the removal of organic water pollutants. A laboratory study of the removal and decomposition of 2-chlorophenol (2-CP) as a toxic organic pollutant was carried out under various conditions with an organophilized clay mineral (hexadecylpyridinium chloride-modified montmorillonite; HDPM) as adsorbent and Degussa P25 TiO 2 as photocatalyst. Three different oxidation processes leading to the degradation of 2-CP were compared: direct photolysis, heterogeneous photocatalysis in a TiO 2 suspension, and the decomposition of substrate adsorbed on HDPM in the presence of TiO 2 . Both the degradation of 2-CP and the formation of intermediates were analyzed by HPLC, the total organic carbon content and the total organic and inorganic chloride contents were measured to monitor the mineralization process, and X-ray diffraction and thermoanalytical measurements were made to characterize the hydrophobic clay adsorbent. The heterogeneous photocatalytic degradation of dissolved (2-CP/UV/TiO 2 ) and desorbed 2-CP (2-CP/HDPM/UV/TiO 2 ) appeared to be equally efficient, whereas direct photolysis of 2-CP was far less efficient in the oxidative destruction. HDPM proved to be a suitable adsorbent, capable of adsorbing toxic organics from water. It was demonstrated that the adsorbent (at relatively high concentration) did not decrease the rate of mineralization of 2-CP. The results confirmed that the adsorbent retains its structure and composition during the mineralization process, and thus it can be reused without regeneration. The combination of adsorption and heterogeneous photocatalysis studied may be an efficient and economical means of accumulating, removing, and oxidizing organic water contaminants, and its application is in accordance with the growing environmental demands.
2009
Recent literature reports about several attempts to immobilize TiO 2 powder on different supporting materials [1-21], when titania is used as photocatalyst for the degradation of hazardous organic compounds in air or water. In fact the simple use of powder catalyst, especially in the nanosized form, has the disadvantage of a difficult sedimentation after the photocatalytic process; in addition TiO 2 nanoparticles, dispersed in the surrounding, may be hazardous, due to their potential inflammatory and cytotoxic effects [22]. TiO 2 was generally supported on SiO 2 glass beads [1], rings [2], and reactor tubular walls [3,4]; fiberglass [5,6]; quartz [7,8]; zeolites [9,10]; perlite [11]; pumice [12]; alumina-based ceramic [13]; stainless steel [14,15]; aluminum [16]; polymeric membranes [17-19], etc. Recently natural fibers began to be used as suitable supports and the cotton material was conveniently adapted inside the photoreactors [20,21]. In spite of the different TiO 2 crystalline phases (anatase, rutile and brookite), most of the literature on immobilized catalysts is focused on the use of commercial P25 photocatalyst or of anatase, due to the small average size of the particles (<50 nm); in fact it is expected that the smaller the particle size the higher the surface area suitable for the catalytic activity. No attention, until lately, was directed to the possibility that other properties beside the surface area, like crystal shape and the oxygen source, could be influent. Very recently we demonstrated that the catalytic activity of TiO 2 in the degradation of phenol (PhOH) in water depends on both the average particle size and the type of oxygen donor (O 2 or H 2 O 2). Specifically, when the oxygen donor was H 2 O 2 , the large crystals of pure rutile or rutile-rich mixtures showed the highest activity; oppositely, when using O 2 , anatase and anatase-rich mixtures are the most active [23,24]. This behavior was attributed to the slow recombination rate of the electron-hole couple in rutile large nanocrystals, which controls the catalytic mechanism when the
Photocatalytic Degradation of 2,4-Dichlorophenol by TiO2 Intercalated Talc Nanocomposite
International Journal of Photoenergy, 2019
Novel nanocomposites have been prepared by intercalating TiO2 nanoparticles into talc. The nanocomposites have been verified by X-ray diffraction (XRD) from the appearance of a characteristic diffraction peak of TiO2. Thermal behavior of the prepared samples is examined by thermogravimetric analyzer (TGA), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS), which have shown no TiO2 particles on the surface of the talc. The TiO2 particles are found in the layers of talc by transmission electron microscopy (TEM) and the Brunauer-Emmett-Teller (BET) method, which have shown the increase of specific surface areas and total pore volumes and the decline of average pore diameters. As the strong adsorption ability of talc can intensify the power of photon absorption and capture-recombination carriers, more than 99.5% of 2,4-dichlorophenol can be degraded in 1 h by the nanocomposite under an ultraviolet lamp in neutral solution and room temperature after reaching ad...
Photocatalytic Phenol Degradation by Silica-Modified Titanium Dioxide
Applied Sciences
Titanium dioxide (TiO2) has been widely applied as a photocatalyst for wastewater treatment due to its high photocatalytic activity and it can remove various harmful organic pollutants effectively. Under heated system, however, TiO2 is prone to agglomeration that decrease its abilities as a photocatalyst. In order to overcome the agglomeration and increase its thermal resistance, addition of silica (SiO2) as supporting material is proposed in this research. Silica or silicon dioxide can be extracted from natural resources such as beach sand. Here, we report the application of a composite photocatalyst of TiO2/SiO2 to remove phenolic compounds in wastewater. The photocatalyst was synthesized by adding SiO2 from beach sand onto TiO2 through impregnation methods. The results of the X-ray diffraction (XRD) showed that TiO2 was present in the anatase phase. The highest crystallinity was obtained by TiO2/SiO2 ratios of 7:1. SEM results showed that the shape of the particles was spherical....
International Journal of Engineering Research and Technology (IJERT), 2015
https://www.ijert.org/preparation-and-characterization-of-different-tio2-modified-montmorillonite-meso-microporous-materials-with-enhanced-photocatalytic-activity https://www.ijert.org/research/preparation-and-characterization-of-different-tio2-modified-montmorillonite-meso-microporous-materials-with-enhanced-photocatalytic-activity-IJERTV4IS090260.pdf A set of TiO2-modified montmorillonite meso-microporous materials, as photocatalysts, was successfully prepared in different ways and evaluated by the photodegradation of 4-nitrophenol (4-NP) in water, since it is a recalcitrant organic pollutant. The effects of photocatalysts' preparation methods on their textural, structural and catalytic properties were tested. To understand the relationship between the photocatalysts structure and performance, these were characterized by X-Ray Diffraction (XRD), UV-spectroscopy, Scanning Electron Microscopy/Energy Dispersive X-ray spectroscopy (SEM/EDX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray fluorescence (XRF), specific surface area and porosity measurements. A high specific surface area (up to 231 m 2 /g), a meso-microporous structure and a high stability have been found for the TiCl4-M and TiCl3-M prepared photocatalysts. In addition, to improve the 4-NP degradation, various parameters' effect was studied such as the type of the photocatalyst, its amount loading, the pH of the 4-NP solution and the initial 4-NP concentration. Then, the 4-NP degradation rate has reached 99% only when Anatase Titanium dioxide was supported on montmorillonite, at pH=5, with 0.2 g/100 mL of photocatalyst (TiCl4-M or TiCl3-M) amount and a 4-NP concentration equal to 20 mg.L-1 .
Adsorbability and photocatalytic degradability of humic substances in water on Ti-modified silica
Journal of Colloid and Interface Science, 2006
From the viewpoint of development of a removal agent for humic substances, we prepared Ti-modified silica gel, SiO 2-Ti, from titanium alkoxide and microsized silica gel. The prepared silica agent was investigated in adsorption and photocatalytic degradation of humic substances in water. In these experiments, four humic substances, commercially available Wako humic acid (Wako-HA), Nordic aquatic humic acid (Nordic-HA), Nordic aquatic fulvic acid (Nordic-FA), and Suwannee river fulvic acid (Suwannee-FA), were used, and Freundlich constants (K F and 1/n) and photodegradation rates were evaluated. Wako-HA, which has the highest aromaticity ratio [Ar-OH]/[COOH] and molecular weight, had the highest adsorbability (K F = 17.5 (mg/g)(L/mg) 1/n , 1/n = 0.67) but the lowest photodegradability (<80%). On the other hand, Suwannee-FA, which has the lowest aromaticity, [Ar-OH]/[COOH] ratio, and molecular weight, afforded lesser adsorbability (K F = 7.1 (mg/g)(L/mg) 1/n , 1/n = 0.39) but the highest photodegradability (>99%). Nordic-HA and Nordic-FA afforded adsorbabilities similar to that for Suwannee-FA, and medium photodegradabilities between those for Wako-HA and Suwannee-FA. Adsorption and photodegradation capacities of SiO 2-Ti were improved with increased Ti content and phosphorescence emission amount, respectively. From XRD analysis, we found that the structure of anatase-type TiO 2 features the Ti modifiers of SiO 2-Ti. Therefore, humic substance molecules effectively interact with the Ti modifiers and are decomposed by OH radicals generated in situ. We hope that SiO 2-Ti will be used as a photodegradation catalyst in water purification plants.
Effect of adsorbents coated with titanium dioxide on the photocatalytic degradation of propoxur
Chemosphere, 1999
Photocatalytic oxidation of pesticides in aqueous media irradiated by UV light is a rapidly growing field of research. Therefore, the treatment technology for degradation of propoxur (an insecticide) using titanium dioxide coated on the supports such as activated carbon, zeolite, brick, quartz and glass beads. was performed in this research. Results show that GACiTiOl is the best complexing agent for oxidizing propoxur because of its adsorption properities. The others follow the sequence: plain TiOz > glass beads > zeolite > brick > quartz. The degradation rate of propoxur with plain TiOz is higher than that with TiOz/GAC complexing agent. But the mineralization rate of propoxur with plain TiOz is lower than that with Ti02IGAC complexing agent. However, it can be concluded that using GAC as the support can improve the photocatalytic efficiency 01998 Elsevier Science Ltd. All rights reserved
SN Applied Sciences, 2019
A facile synthesis of polyethylene glycol-templated silica-titania (PEG-templated SiO 2-TiO 2) nanoparticles has been carried out using sol-gel reactions by partial-prehydrolysis of tetraethoxysilane and titanium isopropoxide. The prepared nanomaterials have been investigated by N 2 adsorption, FTIR, FT-Raman, TG-DSC, XRD, TEM, DLS, 13 C and 29 Si MAS NMR and XPS analysis to characterize the phase composition and microstructure of the samples. The photocatalytic performance of the SiO 2-TiO 2 nanoparticles was evaluated by photooxidative degradation of the alkylphenol derivatives aqueous solution. It was shown that their photoactivity in the removal of alkylphenol ethoxylates from aqueous solution was higher than for porous titania nanoparticles. The incorporation of PEG template into the inorganic network with subsequent formation of nanoporous structure will increases the efficiency of the SiO 2-TiO 2 nanoparticles. It was shown that the polymeric species played a significant role in the generation of pores by the hybridization with inorganic oxides on the molecular scale due to hydrogen bonds taking place at the ether moieties. The advantages of including thermally removable PEG template in terms of increasing surface, mesoporosity and photon absorbance at UV-visible wavelengths to give nanoengineered photocatalytic materials is described.