Synthesis, Characterization, and Visible Light Photocatalytic Activity of Nanosized Carbon Doped Zinc Oxide

ZnO precursor was prepared using microemulsion method. Precursor was calcined in a furnace in a temperature range of 300–500°C with an interval of 100°C. Precursor and calcined nanopowders were characterized using TG/DTA, XRD, FT-IR, EDX, TEM, SEM, and particle size analyzer. Precursor calcined at 300°C for 2 h contains 3.87% carbon (C). Increase in calcination temperature of precursor shows decrease in C content. Precursor calcined at 500°C for 2 h yielded pure ZnO. UV-visible spectrophotometer was used to analyze the concentration of MG during the degradation process. In presence of visible light C doped ZnO obtained by calcining precursor at 300°C shows better photocatalytic activity for MG degradation. Parameters affecting the photocatalytic process such as calcination temperature of catalyst, catalyst loading, MG concentration, and pH of solution have been investigated.

Photocatalytic Degradation of Indigo Carmine Dye Using Calcium Oxide

Calcium oxide was used as photocatalyst for the degradation of indigo carmine dye solution in the visible, long UV, and short UV radiation. We have investigated the effectiveness of degradation of indigo carmine dye solution at pH 9 and 12 using calcium oxide with the particle size of 30–36 nm by varying the concentration, dose of adsorbent, and duration. It has been found that the degradation of indigo carmine dye is effective at pH = 9, when 0.12 g of calcium oxide was used. The nature of interaction between calcium oxide and indigo carmine dye was discussed.

Photoinduced Aromatization of Asymmetrically Substituted 1,4-Dihydropyridine Derivative Drug Cilnidipine

The antihypertensive drug Cilnidipine (1) is photolabile under UV-A light. Irradiation of a chloroform solution of Cilnidipine under aerobic and anaerobic conditions produces a common photoproduct which was isolated as 2-methoxyethyl-3-phenyl-2-propenyl pyridine dihydro-2,6-dimethyl-4-(3-nitrophenyl) pyridine-3,5-dicarboxylate (2). The formation of products was explained by photochemical aromatization of Cilnidipine.

Silver(I) Catalyzed Photochemical Oxidation of Methylene Blue and Safranine-O by Peroxydisulphate: A Green Chemical Approach

In the present investigation, a comparative study of silver(I) catalysed photochemical oxidation of methylene blue (MB) and safranine-O (SO) by peroxydisulphate has been reported. The effect of different parameters, such as pH, concentration of peroxydisulphate, silver nitrate, and light intensity, on the reaction rate has been observed. The progress of the photochemical oxidation was monitored spectrophotometrically. The optimum conditions for photochemical oxidation were achieved. The dyes were completely oxidized and degraded into CO2 and H2O. A tentative mechanism for silver(I) catalyzed photochemical oxidation of these dyes by peroxydisulphate has also been proposed.

Photocatalysis of Titanium Dioxide for Water Disinfection: Challenges and Future Perspectives

The performance of metal oxides such as titanium dioxide (TiO2), in the conversion of solar energy into chemical energy, is determined by semiconducting properties. The conversion process is closely related to the light-induced reactivity between oxide semiconductors and water, which may lead to partial water oxidation and consequently water disinfection. Key performance-related properties are considered here, including light absorption, light-induced ionisation over the band gap, charge separation, charge transport, charge transfer, and the chemical reactions taking place at anodic and cathodic sites. Optimisation of these interconnected performance-related properties is discussed, along with the photocatalytic application in water disinfection.

Effect of the Amount of Water in the Synthesis of B-TiO2: Orange II Photodegradation

A series of boron-doped TiO2 photocatalysts (2% B-TiO2) with different water/alkoxide molar ratio were synthesized by conventional sol-gel method. The prepared samples were characterized by BET measurement, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIRS), and diffuse-reflectance UV-vis. The phase anatase was present, but unexpectedly a small amount of rutile phase was formed with low and excess water in the synthesis. Additionally it has been observed that the increase in the molar ratio of water significantly increases the values of band gap energy and the specific surface area. Results showed that degradation of Orange II azo dye increases with surface area, particle size, boron, and water content in photocatalysis. The boron species were introduced in the tricoordinated form.

The Photocatalytic Oxidation of 4-Chlorophenol Using Bi2WO6 under Solar Light Irradiation

This report discusses the effects of the initial concentration of 4-chlorophenol (4-CP) on its solar light photoinduced oxidation/mineralization kinetics on Bi2WO6 catalyst. Photocatalytic degradation followed the Langmuir-Hinshelwood (L-H) mechanism. From the kinetic data the Langmuir adsorption equilibrium constant of 4-CP on the Bi2WO6 surface and the L-H maximum reaction rate for 4-CP oxidation have been evaluated. Chromatographic and spectroscopy studies show the presence of p-benzoquinone and maleic acid as the main reaction products; these compounds first increase and then decay until they disappear. Chemical oxygen demand (COD) and produced CO2 measurement show that photocatalytic mineralization of the phenolic compound was readily possible in a wide concentration range.

Irradiation Effect on Stability of Plasticized Poly(Fluorostyrene) Isomers in Solution

The UV irradiation and blending effects on stability of Poly(Fluorostyrene) isomers in solution were studied at different intervals of irradiation time in presence of air. The increase in irradiation time of these isomers caused an increase in the intensity of the absorption band and an increase in the intensity of the absorption of new broad band at longer wavelength, thus indicating a possibility of photodegradation of polymeric chains. The influence of added dioctyl phthalate and dioctyl terephthalate plasticizers on photooxidative degradation was also investigated and was found to increase the photodegradation processes in polymeric chains. On the other hand, the intensity of excimer and monomer fluorescence bands maxima was also found to decrease with increase in irradiation times. These changes may be attributed to the formation of new photoproducts resulted from the photodegradation of irradiated polymeric chains. The decrease in polarity of used solvents caused a considerable enhancement to the intensity of the polymer fluorescence band and accelerated photodegradation. A proposed mechanism is suggested to account for the effects of added plasticizers, the increase in irradiation time, and polarity of solvents on photodegradation and photooxidation processes in polymeric chains.

Novel Method for Breakthrough Removal of Azo Dye from Aqueous Environment Using Integrated Coagulation and Fenton Process

Fenton process has proven to be efficient in the removal of color and chemical oxygen demand (COD) from the aqueous environment. However, the environment, health, and economic constraints on the dosage of hydrogen peroxide represent a limitation towards a wide practical use of this approach. In this study, a novel approach is proposed; this includes the treatment with ferrous oxide through coagulation followed by integrated Fenton process. However, the excess ferrous and ferric ions from the coagulation step were utilized in the advanced oxidation step using hydrogen peroxide. The advantage here is the usage of the minimum number of hydrogen peroxide to comply with all the international environmental, safety, and health regulations. The aim of this study is to evaluate the capabilities of the unique integrated process of coagulation and Fenton process for color and COD removal of azo dye in an aqueous environment. The optimum operating parameters such as coagulant dose, temperature, and the dose of hydrogen peroxide were determined. This was done with the objective to optimize the percentage removal of color and COD. The main properties of the treated wastewater such as pH and COD content were measured after treatment against the Malaysian standard part B. The results show that the proposed method was successful for the removal of the color and COD from the aqueous environment to reach more than 99% with the new method.