Elongated titania nanostructures as efficient photocatalysts for degradation of selected herbicides (original) (raw)
Related papers
Journal of Hazardous Materials, 2010
The aim of this work was to study the efficiency of Fe-and N-doped titania suspensions in the photocatalytic degradation of the herbicides RS-2-(4-chloro-o-tolyloxy)propionic acid (mecoprop, MCPP), (4-chloro-2-methylphenoxy)acetic acid (MCPA), and 3,6-dichloropyridine-2-carboxylic acid (clopyralid, CP) under the visible light ( ≥ 400 nm) irradiation. The obtained results were compared with those of the corresponding undoped TiO 2 (rutile/anatase) and of the most frequently used TiO 2 Degussa P25. Computational modeling procedures were used to optimize geometry and molecular electrostatic potentials of MCPP, MCPA and CP and discuss the obtained results. The results indicate that the efficiency of photocatalytic degradation is greatly influenced by the molecular structure of the compound. Lowering of the band gap of titanium dioxide by doping is not always favorable for increasing photocatalytic efficiency of degradation.
Photocatalytic degradation of 2,4-D and 2,4-DP herbicides on Pt/TiO2 nanoparticles
Journal of Saudi Chemical Society, 2015
Titanium dioxide was synthesized by the sol-gel method and platinum supported on titanium dioxide were prepared by a wet impregnation chemical process at different platinum contents. The prepared samples were dried over night at 110°C and then calcined at 500°C for 4 h. Structural and morphological characterization has been carried out by means of X-ray diffraction (XRD), differential scanning calorimetry-thermogravimetric analysis (DSC-TGA), Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller surface area measurement (BET) and transmission electron microscopy coupled to the energy dispersive spectroscopy (TEM/EDX). The adsorption performance and photocatalytic activity of the samples were investigated using two chlorophenoxy herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-(2,4-dichlorophenoxy) propionic acid (2,4-DP) as models of organic pollutants in water. The obtained results show that Pt/TiO 2 exhibited higher photocatalytic activity than TiO 2 particles
International Journal of Photoenergy, 2008
We present the photocatalytic degradation of a water soluble sulfonylurea herbicide: azimsulfuron in the presence of titania nanocrystalline films. Efficient photodegradation of herbicide was achieved by using low-intensity black light tubes emitting in the Near-UV. The degradation of the herbicide follows first-order kinetics according to the Langmuir-Hinshelwood model. Intermediate products were identified by the LC-MS-MS technique during photocatalytic degradation. In order to increase photodegradation rate of the herbicide, we examined the effect of titania modification by depositing noble metals at various quantities and valence states. The presence of platinum at neutral valence state and optimum concentration induced higher photodegradation rates while silver-modified titania exhibited similar photocatalytic rates with those obtained with pure nanocrystallineTiO2films. Finally, the effect of initial pH value was also examined. Acidic or alkaline media were unfavorable for azi...
Environmental Science and Pollution Research, 2014
The objective of this work is double-firstly to explore the photocatalytic efficiency of five different commercial TiO 2 catalysts in the photodegradation of a mixture of pesticides classified by the EU as priority pollutants and secondly to analyze the correlation between their physicochemical properties and the inhibition of the studied photocatalytic process when natural water was employed. Photocatalytic efficiencies when ultrapure water was used seem to point out that surface area was not a prerequisite for the photodegradation of the selected mixture of pesticides. On the other hand, significant differences in total organic carbon (TOC) conversions were obtained with the two studied water compositions. On one side, Evonik materials appear to be mostly inhibited when natural water was employed, whereas on the other, it should be remarked that anatase Sigma-Aldrich (SA) and, particularly, Hombikat UV100 (HBK) materials presented a very limited photo-efficiency inhibition or even a higher initial rate of TOC removal when a natural water matrix was used, probably due to their specific surface properties (PZC, S BET ). Therefore, heterogeneous photocatalysis has proved to be a promising technology for the degradation of the selected mixture of pesticides where the final photoefficiency of the five commercial titania catalysts studied here responds to a complex balance between its surface and structural properties.
Photochemical and photocatalytic evaluation of 1D titanate/TiO2 based nanomaterials
Applied Surface Science, 2017
One-dimensional (1D) titanate based nanomaterials were synthesized following an alkaline hydrothermal approach of commercial TiO 2 nanopowder. The morphological features of all materials were monitored by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and also Brunauer-Emmett-Teller (BET) technique. In addition the photochemical behaviour of these nanostructured materials were evaluated with the use of laser induced luminescence (LIL), ground-state diffuse reflectance (GSDR), and laser-flash photolysis in diffuse reflectance mode (DRLFP). The mixed titanate/TiO 2 nanowires presented the least intense fluorescence spectra, suggesting the presence of surficial defects that can extend the lifetime of the excited charge carriers. A fluorescent 'rhodamine-like' dye was adsorbed onto different materials and examined via photoexcitation in the visible range to study the self-photosensitization mechanism. The presence of the radical cation of the dye and the degradation kinetics, when compared with a neutral substrate-cellulose, provided significant evidences regarding the photoactivity of the different materials. Regarding all the materials under study, the nanowires exhibited a strong photocatalytic efficiency, for the adsorbed fluorescent probe. The photocatalytic mechanism was also considered by studying the photodegradation capability of the titanate based materials in the presence of an herbicide, Amicarbazone, after ultraviolet (UVA) photoexcitation.
Journal of Nanomaterials, 2015
The presence of both organic and inorganic pollutants in water due to industrial, agricultural, and domestic activities has led to the global need for the development of new, improved, and advanced but effective technologies to effectively address the challenges of water quality. It is therefore necessary to develop a technology which would completely remove contaminants from contaminated waters. TiO2(titania) nanocatalysts have a proven potential to treat “difficult-to-remove” contaminants and thus are expected to play an important role in the remediation of environmental and pollution challenges. Titania nanoparticles are intended to be both supplementary and complementary to the present water-treatment technologies through the destruction or transformation of hazardous chemical wastes to innocuous end-products, that is, CO2and H2O. This paper therefore explores and summarizes recent efforts in the area of titania nanoparticle synthesis, modifications, and application of titania n...
ChemEngineering
The photocatalytic degradation of picloram (4-amino-3,5,6-trichloro-2-pyridincarboxylic acid), which is one of popular acidic herbicide, was investigated with the existence of titanium oxide (TiO2) under sunlight. The total photocatalytic degradation of 20 ppm of picloram was occurred within 30 min irradiation with TiO2, while a negligible degradation was found without TiO2 under sunlight. The influence of various parameters, like TiO2 dosage, solution initial pH, intensity of light, reaction temperature and irradiation time, was found during the photocatalytic degradation of picloram. The mineralization of picloram was proved by the deterioration of total organic carbon (TOC) of the photocatalytic process. The pseudo–first order kinetics of photocatalytic degradation was obtained according to the Langmuir–Hinshelwood model, and the reaction rate constant was 17.6 × 10−2 min−1. Chloride ion, ammonium ion, nitrate ion and CO2 were erected as the final products after completing the ph...
Effects of heat and peroxide treatment on photocatalytic activity of titanate nanotubes
Catalysis Today, 2015
The influence of structural, morphological and surface properties on photocatalytic activity of pristine and modified titanate nanotubes was carefully described and discussed in the following study. 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 threefold 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 H 2 O 2 medium resulted in deteriorated photocatalytic oxidation of the model compound, due to recovery of surface Ti 3+ defect sites, leading to increased e −-h + recombination and decreased oxygen adsorption. In addition, a carbon-based elemental analysis of the heat-treated TNTs (TNT 500) and standard TiO 2 P25 stressed the potential of tailor-made crystalline TNTs to be applied as photocatalysts for long-term removal of aqueous organics, due to low accumulation of carbonaceous deposits during the photodegradation runs.
Desalination, 2009
The work describes a study of the oxidation power of nitrogen-doped titanium dioxide (TiO 2 ) suspensions for photocatalytic degradation of the herbicides RS-2-(4-chloro-o-tolyloxy)propionic acid (mecoprop) and (4-chloro-2methylphenoxy)acetic acid (MCPA) using various light sources. The nitrogen-doped TiO 2 crystalline nanopowder was synthesized by calcination of the hydrolysis product of titanium tetraisopropoxide in ammonia. The product was an anatase crystal phase with mean particle diameter 7-15 nm and specific surface area of 121±1 m 2 g !1 . It showed visible-light photocatalytic activity at about 530 nm. Although nitrogen concentration in nitrogen-doped TiO 2 is low (<1 atomic %), it appeared to be about 1.5 times more efficient than TiO 2 Degussa P25 when artificial visible light was used for mecoprop and MCPA degradation, and about six times compared to direct photolysis. It was found that the optimal content of nitrogen-doped TiO 2 was 4 mg cm !3 . The photodegradation of the herbicide aromatic ring takes place simultaneously with chloride evolution, whereby the reaction in both cases follows first-order kinetics.
BACKGROUND: The presence of pesticides in surface and ground waters can trigger serious environmental problems, particularly in those areas where agriculture is the major economic activity. In this respect, photochemical advanced oxidation processes may be employed to decontaminate such matrices. RESULTS: Semiconductor photocatalysis was employed to treat a mixture of four commercial pesticides (oxydemethon-methyl, methidathion, carbaryl and dimethoate at 25 mg L −1 each). Laboratory scale experiments under UV-A irradiation were performed to evaluate the relative activity of six commercially available titania samples at 0.5 g L −1 concentration, with Evonik P25 (a 75:25 mixture of anatase:rutile) being the most effective one in terms of pesticides degradation. Experiments were then performed in a pilot plant reactor under natural sunlight leading to quantitative removal of pesticides in less than 300 min; this was accompanied by a substantial reduction of acute toxicity to Vibrio fischeri (i.e. from an initial value of 50% to 15%), as well as moderate mineralization, i.e. 40% COD and 25% DOC removal.