http://repository.ias.ac.in/39608/1/49_pub.pdf

A review of imperative technologies for wastewater treatment I: oxidation technologies at ambient conditions

In this paper, visible light assisted degradation of various pollutants using different methods has been briefly reviewed. These methods have been broadly divided into two main categories. In the first category, the use of TiO2 semiconductor facilitating the photooxidative degradation of organic pollutants has been presented. This semiconductor has been treated in several ways. A major aim of these treatments is to maximize the range of wavelength in the visible light region for wastewater treatment. In the second category, various ways of degrading organic pollutants without the use of TiO2 semiconductor have been briefly outlined. The role of Fe(II)/Fe(III), etc., species in the sensitization process of various substrates helping it in the process to photocatalytic degradation reactions of organic pollutants has been highlighted. Also, the usage of semiconductors other than TiO2 has been critically analyzed.

Visible light induced photocatalytic degradation of organic pollutants

Photocatalysis promises a solution to challenges associated with the intermittent nature of sunlight which is considered as renewable and ultimate energy source to power activities on Earth. This review aims to provide a broad overview of the field. Insight into natural photosynthesis is discussed first, which provides a scientific basis for most efforts on photocatalysis. Afterwards, the details of four existing types of photocatalysis are presented, namely photosynthesis by plants, photosynthesis by microalgae, photocatalysis by suspension and photoelectrocatalysis. Detailed analyses of simple photocatalysts and integrated photocatalytic systems are followed to shed light on the different functionalities of different components in a working photocatalyst. Special attention is given to the roles played by surface and interface chemical phenomena. Lastly, perspectives on artificial photosynthesis are discussed briefly at the end.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/aenm.201700841

Photocatalysis: Basic Principles, Diverse Forms of Implementations and Emerging Scientific Opportunities

The degradation of methyl tert-butyl ether (MTBE) was investigated in the aqueous solution of coated ZnO onto magnetite nanoparticale based on an advanced photocatalytic oxidation process. The photocatalysts were synthesized by coating of ZnO onto magnetite using precipitation method. The sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibration sample magnetometer (VSM). Besides, specific surface area was also determined by BET method. The four effective factors including pH of the reaction mixture, Fe3O4/ZnO magnetic nanoparticles concentration, initial MTBE concentration and molar ratio of [H2O2]/ [MTBE] were optimized using response surface modeling (RSM). Using the four-factor-three-level Box–Behnken design, 29 runs were designed considering the effective ranges of the influential factors. The optimized values for the operational parameters under the respective constraints were obtained at PH of 7.2, Fe3O4/ZnO concentration of 1.78 g/L, initial MTBE concentration of 89.14 mg/L and [H2O2]/ [MTBE] molar ratio of 2.33. Moreover, kinetics of MTBE degradation was determined under optimum condition. The study about core/shell magnetic nanoparticles (MNPs) recycling were also carried out and after about four times, the percentage of the photocatalytic degradation was about 70%.

/pdf/response-surface-analysis-of-photocatalytic-degradation-of-413vu4euhe.pdf

Response surface analysis of photocatalytic degradation of methyl tert-butyl ether by core/shell Fe3O4/ZnO nanoparticles.

2.7. Redox Deprotections 221 3. Thiol Protecting Groups 223 4. Carboxy Protecting Groups 223 4.1. Protection 224 4.2. Deprotection 226 5. Carbonyl Protecting Groups 227 5.1. Acetals 227 5.1.1. Protection 227 5.1.2. Deprotection 231 5.2. Dithioacetals 233 5.2.1. Protection 233 5.2.2. Deprotection 235 5.3. 1,3-Oxathiolanes 237 5.4. 1,1-Diacetates (Acylals) 238 5.4.1. Protection 238 5.4.2. Deprotection 239 5.5. Nitrogenous Derivatives 240 5.5.1. Protection 240 5.5.2. Deprotection 241 6. Amino Protecting Groups 242 6.1. Protection 242 6.2. Deprotection 244 7. Concluding Remarks 246 8. Acknowledgments 246 9. Abbreviations 246 10. References 246

Protection (and deprotection) of functional groups in organic synthesis by heterogeneous catalysis.

The photocatalytic oxidation of aqueous solutions of 2-mercaptobenzothiazole (MBT), 2-mercaptobenzimidazole (MBI), 2-mercaptobenzoxazole (MBO), 2-mercaptopyridine (MP), para-tolylmercaptan (PTM) was investigated over a heterogeneous catalyst of TiO2, in a photocatalytic reactor. The effect of some physical and chemical parameters such as amount of catalyst, flow of oxygen, pH and time of irradiation were studied in order to optimise the process. These mercaptans are almost completely mineralised to carbon dioxide, ammonia and sulphate ion by photocatalytic method. The results obtained from photocatalytic oxidation of MBT have led us to propose a compound with the sum formula of benzothiazol-2-sulfonate (BTSO3) to be a main intermediate.

Photocatalytic mineralisation of mercaptans as environmental pollutants in aquatic system using TiO2 suspension

Efficient regio- and stereoselective ring opening of epoxides with alcohols, acetic acid and water catalyzed by ammonium decatungstocerate(IV)

Potassium dodecatangestocobaltate trihydrate (K 5 CoW 12 O 40 ·3H 2 O): a mild and efficient catalyst for the tetrahydropyranylation of alcohols and their detetrahydropyranylation

Novel catalytic acetylation and formylation of alcohols with potassium dodecatungstocobaltate trihydrate (K5CoW12O40·3H2O)

BACKGROUND: Over the past several decades methyl tert-butyl ether (MTBE) as additive to gasoline, intended to either boost ratings of fuel or to reduce air pollution, has been accepted worldwide. Since MTBE has high water solubility, the occurrence of fuel spills or leaks from underground storage tanks or transferring pipeline has led to the contamination of natural waters. In this study the degradation of aqueous MTBE at relatively high concentrations was investigated by a UV-visible/ZnO/H2O2 photocatalytic process. The effects of important operational parameters such as pH, amount of H2O2, catalyst loading and irradiation time were also investigated. Concentration of MTBE and intermediates such as tert-butyl formate and tert-butyl alcohol were measured.



RESULTS: Time required for complete degradation increased from 20 to 150 min when the initial concentration was increased from 10 to 500 mg L−1. The first-order rate constants for degradation of MTBE were estimated to be 0.183–0.022 min−1 as the concentration increased from 10 to 500 mg L−1. Study of the overall mineralization monitored by total organic carbon analysis showed that at an initial concentration of 100 mg L−1 MTBE complete mineralization was obtained after 100 min under UV-visible/ZnO/H2O2 photocatalysis.



CONCLUSION: The data presented in this paper clearly indicated that UV-visible/ZnO/O2 as an advanced oxidation process provides an efficient treatment alternative for the remediation of MTBE-contaminated waters. Copyright © 2008 Society of Chemical Industry

Bahram Yadollahi

Papers

Photocatalytic mineralisation of mercaptans as environmental pollutants in aquatic system using TiO2 suspension

Efficient regio- and stereoselective ring opening of epoxides with alcohols, acetic acid and water catalyzed by ammonium decatungstocerate(IV)

Potassium dodecatangestocobaltate trihydrate (K 5 CoW 12 O 40 ·3H 2 O): a mild and efficient catalyst for the tetrahydropyranylation of alcohols and their detetrahydropyranylation

Novel catalytic acetylation and formylation of alcohols with potassium dodecatungstocobaltate trihydrate (K5CoW12O40·3H2O)

Photocatalytic degradation of methyl tert-butyl ether (MTBE) in contaminated water by ZnO nanoparticles