Visible-light photocatalytic degradation of herbicide mecoprop in n-doped TiO2 suspensions

In this study, the nitrogen-doped TiO2 crystalline nanopowder was synthesized by calcination of the hydrolysis product of titanium tetraisopropoxide in ammonia. Obtained nanopowder was characterized by XRD and UV-Vis reflection techniques. The kinetics of visible-light (400-800 nm) photocatalytic degradation of herbicide mecoprop in N-doped TiO2 nanopowder aqueous suspensions was investigated and compared to results obtained for undoped TiO2.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Potential of TiO2 with various au nanoparticles for catalyzing mesotrione removal from wastewaters under sunlight

Nowadays, great focus is given to the contamination of surface and groundwater because of the extensive usage of pesticides in agriculture. The improvements of commercial catalyst TiO2 activity using different Au nanoparticles were investigated for mesotrione photocatalytic degradation under simulated sunlight. The selected system was 2.43 × 10−3% Au–S–CH2–CH2–OH/TiO2 (0.5 g/L) that was studied by transmission electron microscopy and ultraviolet-visible (UV-Vis) spectroscopy. It was found that TiO2 particles size was ~20 nm and ~50 nm, respectively. The Au nanoparticles were below 10 nm and were well distributed within the framework of TiO2 . For 2.43 × 10−3% Au–S–CH2–CH2–OH/TiO2 (0.5 g/L), band gap energy was 2.45 eV. In comparison to the pure TiO2, addition of Au nanoparticles generally enhanced photocatalytic removal of mesotrione. By examining the degree of mineralization, it was found that 2.43 × 10−3% Au–S–CH2–CH2–OH/TiO2 (0.5 g/L) system was the most efficient for the removal of the mesotrione and intermediates. The effect of tert-butanol, NaF and ethylenediaminetetraacetic acid disodium salt on the transformation rate suggested that the relative contribution of various reactive species changed in following order: h+ >•OHads >•OHbulk. Finally, several intermediates that were formed during the photocatalytic treatment of mesotrione were identified. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Photocatalytic activity of TiO2 nanoparticles modified with dopamine

Photocatalytic activity of bare colloidal TiO2 nanoparticles (NPs, d~45Å) and surface modified with dopamine was obtained following degradation reaction of herbicide RS-2-(4-chloro-o-tolyloxy)propionic acid (mecoprop, MCPP, C10H11ClO3) under UV light irradiation. Results indicated that inner sphere charge transfer (CT) complex is formed on the surface of TiO2 NPs due to modification with dopamine which induced decreasing of the photocatalytic efficacy of TiO2 NPs

Synthesis and Characterization of Rutile TiO2Nanopowders Doped with Iron Ions

Titanium dioxide nanopowders doped with different amounts of Fe ions were prepared by coprecipitation method. Obtained materials were characterized by structural (XRD), morphological (TEM and SEM), optical (UV/vis reflection and photoluminescence, and Raman), and analytical techniques (XPS and ICP-OES). XRD analysis revealed rutile crystalline phase for doped and undoped titanium dioxide obtained in the same manner. Diameter of the particles was 5–7 nm. The presence of iron ions was confirmed by XPS and ICP-OES. Doping process moved absorption threshold of TiO2into visible spectrum range. Photocatalytic activity was also checked. Doped nanopowders showed normal and up-converted photoluminescence

Photocatalytic removal of the herbicide clopyralid from water

The stability of the herbicide clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) was studied under different experimental conditions of pH, illumination and initial substrate concentration. It was found that in the pH interval from 1.0 to 9.0 in the presence/absence of daylight, clopyralid solutions were stable for at least a period of two months. The kinetics of the photocatalytic degradation of clopyralid in aqueous suspensions of TiO2 (Degussa P25) under UV and visible light, as well as of direct photolysis using the same radiation sources, were also investigated. It was found that the rate of photocatalytic degradation in the presence of UV light was more than five times higher compared to direct photolysis, whereas in the presence of visible light, the corresponding rates of photocatalytic/photolytic degradation were much lower (more than 15 times). The reaction in the investigation concentration range is zero-order with respect to the degradation of the clopyralid pyridine moiety, with a reaction rate of 3.4×10−6 mol dm-3 min-1 and an adsorption coefficient of the substrate of 2.5×104 dm3 mol‑1

Nitrogen-doped TiO2 suspensions in photocatalytic degradation of mecoprop and (4-chloro-2-methylphenoxy)acetic acid herbicides using various light sources

The work describes a study of the oxidation power of nitrogen-doped titanium dioxide (TiO2) suspensions for photocatalytic degradation of the herbicides RS-2-(4-chloro-o-tolyloxy) prop ionic acid (mecoprop) and (4-chloro-2methylphenoxy)acetic acid (MCPA) using various light sources. The nitrogen-doped TiO2 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 rim. Although nitrogen concentration in nitrogen-doped TiO2 is low ( LT 1 atomic %), it appeared to be about 1.5 times more efficient than TiO2 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 TiO2 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

Photocatalytic degradation of selected herbicides in aqueous suspensions of doped titania under visible light irradiation

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 (lambda GT = 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. (C) 2010 Elsevier B.V. All rights reserved

Photocatalytic activity of synthesized nanosized TiO2 towards the degradation of herbicide mecoprop

The kinetics and possible mechanism of the photocatalytic degradation of herbicide mecoprop, in UV illuminated aqueous colloids of synthesized nanosized TiO2 were investigated. The rate of degradation was studied by H-1 NMR, UV spectrometry, as well as by potentiometric titrimetric determination of generated chloride. The catalyst dosage and effects of other kinetic factors on the photocatalytic degradation, such as initial substrate concentration, temperature and type of TiO2 were investigated as well. The degradation rates were found to be strongly influenced by the above parameters. It was found that photocatalytic efficiency is lower and that a smaller number of observed organic intermediates (only 4-chloro-2-methylphenol and acetic acid) was detected than those observed in the presence of TiO2 (Degussa P-25). Kinetics of the degradation were also monitored for direct photolysis, as well as for solar degradation in the presence and in the absence of TiO2. (C) 2004 Elsevier B.V. All rights reserved

Elongated titania nanostructures as efficient photocatalysts for degradation of selected herbicides

Titanium dioxide nanotubes (TNT) were synthesized via hydrothermal method and calcined at various temperatures. The obtained calcined TiO2 nanomaterials with specific elongation orientation were characterized by transmission and scanning electron microscopy (TEM, SEM), X-ray diffraction (XRD), UV/Vis diffuse reflection spectroscopy (DRS), Laser Doppler electrophoresis (LDE) and their textural properties were evaluated. The photocatalytic activity of obtained nanopowders was evaluated considering photodegradation rate of herbicide clomazone, rarely studied herbicide. The influence of calcination temperature of catalysts with elongated morphology on their photocatalytic activity was evaluated. The best results were obtained with TNT annealed at 700 degrees C, which can be assigned to the best balance between crystal structure, morphology and surface properties of nanoparticles induced by annealing. Also, the photocatalytic degradation rates of another two herbicides (picloram, and mecoprop) were compared, due to possibility that the efficiency of photo catalytic degradation is greatly influenced by the molecular structure. The mineralization degree of selected herbicides in the presence of TiO2 based photocatalysts was evaluated applying total organic carbon (TOC) measurements. (C) 2014 Elsevier B.V. All rights reserved

Rutile nanostructures: Synthesis, characterization and potential application in photocatalytic processes

Titanium dioxide is one of the most studied semiconductors because of its wide range of potential technological applications including pigments, cosmetics, photovoltaic cells and catalysis. TiO2 has three most commonly encountered crystalline polymorphs: anatase, brookite and rutile. The possible application of TiO2 critically depends on crystalline structure, size and shape of the particles. Rutile has the highest density and refractive index and is widely employed in pigments and cosmetic industry. TiO2 is transparent in the visible light region; its band gap is 3.0 eV for rutile and 3.2 eV for anatase crystalline phase. By doping or sensitization, it is possible to improve the optical activity of TiO2 and to move its absorption threshold into the visible light region. The subject of this chapter is different rutile nanostructures of pure and Fe3+- doped titania which were synthesized by co-precipitation in acidic aqueous solution. Obtained materials were characterized by structural (XRD), morphological (TEM and HRTEM), optical (UV/vis absorption, reflection, and photoluminescence), and analytical (XPS and ICP-OES) techniques. Also, photo-catalytic activity measurements were performed, using photo-degradation of specific herbicides as model systems. Applied synthetic procedure resulted in formation of flower like agglomerates of 200-400 nm in diameter. Agglomerates represent assembly of nano-rods consisted of “chains” of spherical particles, 5-7 nm in diameter, most likely interconnected through the so-called oriented attachment or grain-rotation induced-grain coalescence (GRIGC) process. The presence of dopant iron ions didn’t distract morphology of rutile nano-particles, nor agglomerates, but significantly changed optical properties of titania compared to pure material. The photoluminescence of pure and Fe-doped rutile nano-particles is characterized with several well-resolved peaks extending in the visible spectral region. Photon energy upconversion from rutile TiO2 nano-particles was also observed at low excitation intensities. The energy of up-converted photoluminescence spans the range of emission of normal photoluminescence. The explanation of photon energy up-conversion involves mid-gap energy levels originating from oxygen vacancies. © 2012 by Nova Science Publishers, Inc