Optimization of Alachlor Photocatalytic Degradation with Nano-TiO2 in Water under Solar Illumination: Reaction Pathway and Mineralization

In the present study, the photocatalytic degradation of alachlor was investigated using TiO2 under sunlight irradiation. The effects of some operational parameters, such as photocatalyst concentration, temperature, pH, sunlight intensity and irradiation time, were optimized. The kinetics of photodegradation was found to follow a pseudo-first-order kinetic law, and the rate constant at optimal condition is 0.245 min−1. The activation energy (Ea) is 6.4 kJ/mol. The alachlor mineralization can be completed under sunlight irradiation after 10 h. The formations of chloride, nitrate and ammonium ions are observed during the photocatalytic degradation. The eight photoproducts were identified by the GC–MS technique. The photodegradation reaction pathways are proposed based on the evidence of the detected photoproducts and the calculated frontier electron densities of the alachlor structure. The photocatalytic degradation treatment for the alachlor wastewater under solar irradiation is simple, convenient and low cost

Studies of Effects of Calcination Temperature on the Crystallinity and Optical Properties of Ag-Doped ZnO Nanocomposites

Ag-doped ZnO nanocomposites are successfully synthesized at different calcination temperatures and times through a simple, effective, high-yield and low-cost mechanochemical combustion technique. Effects of calcination temperature on the crystallinity and optical properties of Ag/ZnO nanocomposites have been studied by X-ray diffraction (XRD), UV−visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL) and X-ray photoelectron spectroscopy (XPS). The XRD patterns of the synthesized Ag/ZnO exhibit a well-crystalline wurtzite ZnO crystal structure. The grain size of Ag/ZnO nanocomposites is found to be 19 and 46 nm at calcination temperatures of 400 °C and 700 °C, respectively. The maximum absorption in the UV region is obtained for Ag/ZnO nanocomposites synthesized at a calcination temperature of 500 °C for 3 h. The peak position of blue emissions is almost the same for the nanocomposites obtained at 300⁻700 °C calcination temperatures. The usual band edge emission in the UV is not obtained at 330 nm excitation. Band edge and blue band emissions are observed for the use of low excitation energy at 335⁻345 nm

PHOTOCATALYTIC DEGRADATION OF FENITROTHION IN WATER WITH TiO2 UNDER SOLAR IRRADIATION

Fenitrothion is widely used as herbicide with strong estrogenic activity, and it can lead to abnormalities of the thyroid gland and can give mutations. Hence, their degradation treatment is necessary for the environment. The photocatalytic remediation under sunlight irradiation is very effective for the degradation of fenitrothion. Fenitrothion is completely degraded during 10 min under the optimized conditions. The influence of various conditions, such as irradiation time, sunlight intensity, pH, temperature, TiO2 loading amount and initial substrate concentration, is investigated on the degradation of fenitrothion. The photocatalytic degradation mechanisms are speculated, from the experimental results with molecular orbital (MO) simulation for frontier electron density. The primary photocatalytic degradation reaction keeps a pseudo first order kinetic law. The activation energy (Ea) and half-life (t1/2) are 20.6 kJ/mol and 1.4 min, respectively. The fenitrothion wastewater photocatalytic treatment may become a good technique under solar irradiation

Optimization of Operating Conditions for Electrochemical Decolorization of Methylene Blue with Ti/α-PbO2/β-PbO2 Composite Electrode

α-PbO2 was introduced into the intermediate layer of an electrode to prevent the separation of the electrodeposited layer and maintain oxidizing power. The resulting Ti/α-PbO2/β-PbO2 composite electrode was applied to the electrochemical decolorization of methylene blue (MB) and the operating conditions for MB decolorization with the Ti/α-PbO2/β-PbO2 electrode were optimized. The morphology, structure, composition, and electrochemical performance of Ti/α-PbO2 and Ti/α-PbO2/β-PbO2 anode were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The optimum operating parameters for the electrochemical decolorization of MB at Ti/α-PbO2/β-PbO2 composites were as follows: Na2SO4 electrolyte 0.05 g L−1, initial concentration of MB 9 mg L−1, cell voltage 20 V, current density 0.05–0.10 A cm−2, and pH 6.0. MB dye could be completely decolorized with Ti/α-PbO2/β-PbO2 for the treatment time of less than one hour, and the dye decolorization efficiency with Ti/α-PbO2/β-PbO2 was about 5 times better, compared with those obtained with Ti/α-PbO2

Photocatalytic Decolorization of Dye with Self-Dye-Sensitization under Fluorescent Light Irradiation

A dye-sensitization technique was applied to effective catalysts—TiO2 and ZnO—under fluorescent light irradiation for Orange II (OII) and Methyl Orange (MO) degradations. Treatments were carried out at different time periods using 20 mg of catalysts and 30 mL of 5 mg/L of OII and MO. The degradation efficiency of OII and MO increased with increasing irradiation time under irradiation of fluorescent light. The photocatalytic activity of ZnO nanoparticles was better compared with that of TiO2 for MO; and the ZnO activity was the same as TiO2 for OII photodegradation. Kinetic behavior was evaluated in terms of the Langmuir–Hinshelwood model (pseudo-first order kinetic). The possible mechanism of photodegradation under fluorescent light was discussed

Small Airway Morphometry and Improvement in Pulmonary Function After Lung Volume Reduction Surgery.

We examined small airway morphometry from resected lung specimens in 25 patients with severe emphysema undergoing lung volume reduction surgery (LVRS) and correlated their pathologic findings to changes in FEV(1) 6 months after LVRS. Patients were classified into two groups: responders had a more than 12% and a more than 200-ml change in FEV(1) at 6 months, and nonresponders had 12% or less and/or 200 ml or less change in FEV(1). Epithelial height (EH) and perimeters and areas of peribronchial smooth muscle, epithelium, and subepithelial space were measured quantitatively. The degrees of interstitial fibrosis, vascular sclerosis, goblet cell hyperplasia, squamous metaplasia, chronic inflammation, peribronchial fibrosis, and bullous disease were assessed semiquantitatively. Despite similar baseline characteristics, nonresponders had a greater EH (0.045 vs. 0.035 mm, p = 0.025), greater EH adjusted for basement membrane perimeter (0.040 vs. 0.011, p = 0.016), greater epithelial area adjusted for basement membrane area (0.561 vs. 0.499, p = 0.040), and less bullous disease (1.7 vs. 2.6, p = 0.011) compared with responders. We found a linear relationship between percentage change in FEV(1) and bullous disease and inverse relationships between percentage change in FEV(1) and interstitial fibrosis, goblet cell hyperplasia, peribronchial fibrosis, and vascular sclerosis. We conclude that small airway morphometry and lung histopathology in patients with severe emphysema have an important influence on changes in FEV(1) 6 months after LVRS