Kinetics of photocatalytic removal of 2-amino-5-chloropyridine from water

Titanium dioxide sensitized photocatalytic degradation of a pyridine pesticide analogue, 2-amino-5-chloropyridine, was investigated by monitoring the pyridine moiety degradation, as well as by monitoring the chloride generated in the process. Effect of the initial substrate concentration on the rate of its degradation is reported. Here we show that the kinetics of both reactions are of the zero-order in the entire investigated concentration range. The Langmuir-Hinshelwood kinetic model successfully described the influence of the initial substrate concentration on the rate of the pyridine moiety degradation. It was found that dechlorination of the substrate takes place by direct photolysis. The differences in the kinetics of pyridine moiety degradation and dechlorination were explained on the basis of the electrostatic potential for the investigated compound

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

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

JSCS–3677 Original scientific paper Photocatalytic removal of the herbicide clopyralid from water

Abstract: 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 TiO 2 (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 2.5×10 4 dm 3 mol-1

Eudicot plant-specific sphingolipids determine host selectivity of microbial NLP cytolysins

Necrosis and ethylene-inducing peptide 1-like (NLP) proteins constitute a superfamily of proteins produced by plant pathogenic bacteria, fungi, and oomycetes. Many NLPs are cytotoxins that facilitate microbial infection of eudicot, but not of monocot plants. Here, we report glycosylinositol phosphorylceramide (GIPC) sphingolipids as NLP toxin receptors. Plant mutants with altered GIPC composition were more resistant to NLP toxins. Binding studies and x-ray crystallography showed that NLPs form complexes with terminal monomeric hexose moieties of GIPCs that result in conformational changes within the toxin. Insensitivity to NLP cytolysins of monocot plants may be explained by the length of the GIPC head group and the architecture of the NLP sugar-binding site. We unveil early steps in NLP cytolysin action that determine plant clade-specific toxin selectivity