Photocatalytic degradations

Heterogeneous photocatalysis is a promising technology especially for environmental remediation. Despite more than a decade of worldwide research in developing photocatalytic efficiency improving techniques, many questions regarding the large scale application of photocatalytic reactors still remain unanswered. Recently, improving the photocatalytic efficiency has gained scientific attention because it might lead to more economical and robust photocatalytic operation for environmental remediation. In this review, fundamental and comprehensive assessments of the photocatalytic concepts and their applications for environmental remediation are reviewed. The existing challenges and strategies to improve the photocatalytic efficiency are discussed. Further, recent developments and future research prospects on photocatalytic systems for environmental applications are also addressed.

Fe-NH2-BDC, a mesoporous metal-organic
framework (MOF) has high surface area. The structural
characteristics of Fe-NH2-BDC have exhibited a good
candidate for application potentialities in gas storage,
separation and heterogeneous catalysis. This MOF is obtained
by the hydrothermal synthesis in a Teflon-lined autoclave at
high temperature (>150oC) under static conditions. However,
this method has several disadvantages such as high
temperature, high pressure, long reaction time, and relatively
low MOF yield. In this study, Fe-NH2-BDC has been
successfully synthesized by using reflux method at lowtemperature.
Structure and properties of materials have been
characterized by using: XRD, IR, SEM, TGA. The study of
reactive photocatalysis has showed that MOF is as catalysts
and the solution of trinitrotoluene (TNT) 50 ppm was
decolorized after an hour under simulated sun-light radiation.

In the last couple of years, an increasing number of dead marine animals that are full of plastic waste which ends up in the seas and oceans has been evident. Actually, micro-plastics (5-1000 μm) have been detected in the stomachs of commercially important fish from the Mediterranean, as well as some drinking water in plastic bottles. Today, humanity is struggling with the presence of micro- and nano-plastics in enormous quantities in the oceans, seas, rivers and lakes. World plastic production almost reached 350 million tonnes in 2017, where China is the largest producer of plastics, 29.4% followed by Europe with 18.5%.
There is experimental evidence that three weeks of UV irradiation generates plastics particles in the nanometer size range. Nanoparticles (1-100 nm) usually exhibit different chemical and physical properties than macroscopic objects based on the same material. At the micro- and nanoscales, polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene (PS) and polyethylene (PE) were observed. Recent study has shown that carbon-based molecules could break down marine microplastics without harming surrounding microorganisms. Successful degradation of low-density polyethylene film (LDPE) in water by using visible light excited heterogeneous zinc oxide photocatalysts was achieved, as well as polyethylene (PE) plastic with polypyrrole/TiO2 (PPy/TiO2) nanocomposite as photocatalyst. Our current knowledge about nanoplastics in the environment is still very limited and only a few scientific publications are available. For this reason, micro- and nanoplastics are considered as an emerging issue of great concern. Photocatalytic degradation of plastics leads to the formation of lower molecular weight intermediates that can be further used as a raw materials for the chemical industry for the production of new petrochemical products or plastics or in organic synthesis. This review provides an overview of the latest catalytic and photocatalytic methods of degradation of microplastics, as well the quantities of global plastic produced in the world and their impact on human health.

Photocatalytic degradation of nitrobenzene (NB) and an azo dye (namely azophloxine) was carried out using zinc oxide (ZnO) nanoparticles which were prepared by electrochemical method using zinc electrodes in aqueous oxalic acid solution. Taguchi methodology was applied for studying the effects of four experimental parameters namely catalyst dosage (g/l), time of reaction (h), pH and H 2 O 2 dose. Degradation efficiency of NB was found to increase with an increase in H 2 O 2 concentration and decrease in catalyst dosage and pH. Maximum NB degradation efficiency of 98% was observed at catalyst dosage=1 g/l, pH=3, H 2 O 2 to C 6 H 5 NO 2 ratio of 7 mol/mol after 5 h of treatment. Similarly, maximum dye degradation efficiency of 58% and color removal efficiency of 78% was observed at catalyst dosage=1.25 g/l, pH=4, H 2 O 2 concentration of 8 mmol/l in 5 h. Overall, prepared ZnO nanoparticles performed better for NB degradation in comparison to azo dye degradation.

A new visible light sensitive photocatalysts based on Zr 1−x V X O 2 (x = 1, 3, 5, and 7) compositions for treatment of organic dyes in wastewater were investigated. Pure and V-doped ZrO 2 samples were prepared by sol-gel techniques. The XRD results of the pure ZrO 2 confirmed the formation of single phase tetragonal structure. Dopant-induced structure transition from the tetragonal to monoclinic phase. Based on SEM micrographs, mixture of spherical-nanorods architectures was formed in all samples with a volume ratio related to V concentration. Enhanced visible light absorption and an amazing red shift in the absorption edge were noticed in V doped ZrO 2 samples. The magnetic properties of V doped ZrO 2 exhibited room temperature ferromagnetism with varied hysteresis loops shape. Zr 0.97 V 0.03 O 2 structure revealed a notable ferromagnetism with complete saturation magnetization of 0.038 emu/g and coercivity of 1200 Oe. Except Zr 0.93 V 0.07 O 2 structure, all V doped ZrO 2 samples showed significant photocatalytic activity when irradiated with visible light. The highest photocatalytic efficiency,~100%, for methylene blue (MB) dye degradation was achieved through Zr 0.95 V 0.05 O 2 catalyst under visible light irradiation time of 150 minutes. Vanadium played a major role in oxygen vacancies formation and separation of photo-induced electron-hole pairs which enriched the visible light photocatalytic activity.

Due to the toxicity effects and endocrine disrupting properties of many organic compounds, their removal from water and wastewater has gained widespread global attention. This review summarizes photocata-lytic degradation of different organic molecules present in wastewaters. This is an overview of photocatalytic degradation with the goal of presenting the technique as an attractive and viable process unit. This process has great potential for replacing other conventional methods for treatment of wastewaters and can be used at the advanced treatment stage. Photocatalytic degradation techniques should be more used in wastewater treatment because with this technique it is possible to decrease contaminants to certain acceptable discharge limits. However, the technique is still not being utilised on an industrial scale. This is mainly due to focus of researchers to study singular contaminants such as alcohols, carboxylic acid, phenol and its derivate, chlorinated aromatic compounds, colours , active pharmaceutical ingredients, and different type of surface active agents. TiO 2 can be used as a photo-catalyst in water purification to degrade organic pollutants.

Iron-doped TiO2 nanopowders with different doping amounts have been prepared by co-precipitation method followed by heat treatment. The obtained materials were structurally, morphologically and analytically characterized by X-ray diffraction (XRD), FT-Raman spectroscopy, diffuse reflectance spectroscopy (DRS) and energy dispersive X-ray spectroscopy (EDX) coupled to scanning electron microscopy (SEM). XRD analysis revealed the major presence of the anatasa crystalline phase for iron-doped and undoped TiO2. SEM confirmed particles sizes among the nanometer scale along with XRD data. The presence of iron ions was validated by EDX-SEM. Diffuse reflectance techniques were carried out to validate the shift of the band edge absorption spectrum of doped TiO2 nanoparticles towards the visible region and to confirm the presence of iron atoms in the TiO2 crystal lattice by the resulting variation of the band gap value of the doped materials. Photocatalytic activity of the nanoparticles under UV and visible radiation was evaluated by means of hydroxyl radicals production through indirect estimation using N,N-dimethyl-p-nitrosoaniline (PNDA)photo-discoloration experiments in aqueous dispersion. Samples containing 1.2 and 5.6 weight % Fe exhibited the highest activities in this study for both conditions.

The heterogeneous photocatalytic degradation of dyes reactive red 120 and reactive blue 4 under ideal solutions and hydrolysates dyes simulating a staining process with an initial concentration of 50 mg • L-1 was studied, using 200 mg • L-1 of TiO2 doped with Fe or N. Total degradation of both dyes was achieved with the addition of an auxiliary oxidizing agent such as hydrogen peroxide (H2O2) at a concentration of 12.0 mM. Such degradation was achieved after one hour of reaction for doped catalysts (N-TiO2 and Fe-TiO2). For solutions of hydrolysed dye that simulated waste water from the textile industry was found that the pH adversely affects dye degradation due to repulsion between the photocatalysts and dyes. In all the studied cases further degradation of reactive red dye 120 was observed relative to reactive blue 4, which can be associated with the complex molecular structure of the second dye.

A suitable model for predicting the product quality of vacuum gas oil (VGO) catalytic hydrocracking is developed. Data were obtained using an experimental catalytic hydrocracking reactor loaded with the Ni-Mo/Al2O3-SiO2 catalyst. A set of experimental runs was conducted under various operating temperatures from 380 to 450 ℃. Three distribution models were used to develop the predictive model. By the discrete lumping model, distillation curves of the cracked products (naphtha, kerosene, diesel, and gas) were obtained using the simulated distillation test. Model validation results showed that the proposed models are capable of predicting the distillation curves of the hydrocracked products accurately. Accuracy and simplicity of the developed model make it suitable to estimate the conversion and also the product distribution of hydrocracking units in refineries.

We report results of density functional theory (DFT) calculations on some colorless aromatic systems adsorbed on a TiO2 nanocluster, in order to explain experimental results regarding the photocatalytic degradation of these pollutants under visible light irradiation. Based on our modeling, we are able to clarify why transparent pollutants can degrade under visible light in the presence of a catalyst that absorbs only in the UV, to explain experimental data regarding differences in the efficiency of the degradation process, and to state the key requirements for effective water-cleaning. For that purpose, we analyze the absorption spectrum of the free and adsorbed molecules, the binding configurations, the matching of the energy levels with the oxide catalyst and the likelihood of the charge-transfer to the substrate. The comparison between several colorless aniline and phenolic systems allows a correlation between the chemical structure and the degradation rate of these pollutants.

Between the end of the 15th century and beginning of the 16th, the Portuguese and the Spanish expanded their empires to the Americas. While the Portuguese soon dedicated to the exploitation of brazilwood, the Spanish came to establish a monopoly in cochineal that would become one of the most important commercial products in the Atlantic until the 19th century. The interdisciplinary investigation presented here, combining Analytical Chemistry and Economic History, aims to explore the impact of the American insect as a commercial product in the global circulation of dyestuffs, and its importance as a red dye in the main centres of textile production in Europe and in Asia, in relation to other local insect dyes.
The historical investigation comprised a comprehensive revision of historical publications and primary printed sources regarding the Iberian transatlantic trade in dyestuffs and their impact on European and Asian dyeing traditions during the Early Modern period. Special focus was given to the acceptance of American cochineal over local insect dye sources, namely kermes, lac and Armenian and Polish cochineal. This research reveals a gradual but clear adoption of the American dyestuff in Europe and in West Asia, although local insect dyes would still have a representative role in on-going practices, especially in East and Southeast Asia.
Chemical research was pursued to evaluate the historical picture presented for the impact of the American dyestuff in Europe and, especially in Asia, to which insufficient historical information was available. Given that previous publications concerning the chemical characterization of insect dyes depicted limitations that compromised the differentiation of cochineal species in red-dyed historical textiles, an ultra high-performance liquid chromatography (UHPLC) method was optimized  to deliver more accurate results. Then, experiments with cochineal and kermes dyes were undertaken following several dyeing parameters. The resulting dyed fibres were characterized with UHPLC, leading to meaningful insights about the behaviour of the colorants’ dye compounds. Subsequent artificial ageing of the dyed fibres and their characterization with mass spectrometry (MS) permitted to characterize, for the first time, photo-degradation compounds in the insect’s colorant. These results were reported to be similar to those for historical fibres and, for this reason, it became possible to compare the experimentally-dyed and historical fibres through partial-least squares discriminant analysis (PLS-DA), for the identification of the cochineal species used to colour the analysed historical fibres.
By combining the results of this successful approach, along with the results for other coloured historical fibres and their contextualization with historical evidence, it was possible to ascribe assertive interpretations about the date and provenance of the investigated textiles. Moreover, successful historical interpretations could be obtained about the dynamics of American cochineal in European and Asian societies throughout the colonial period. Therefore, the interdisciplinary combination of chemical and statistical methods developed here, along with historical evidence, has proven to be an important approach that should be adopted in future projects for the characterization of insect dyes in cultural heritage objects.

... Basheer Hasan Diya'uddeen ∗ , Wan Mohd Ashri Wan Daud, AR Abdul Aziz ... ozone, H2O2, HOCl and chlorine, the oxidation potentials are 2.07, 1.78, 1.49, and 1.36, respectively (Al-Rasheed, 2005). ... This is achieved mechanically by gravity in API separators or separation tanks ...

In this study, pure ZnO, CeO2 and ZnO/CeO2 nanocomposites were synthesized using a thermal decomposition method and subsequently characterized using different standard techniques. High-resolution X-ray photoelectron spectroscopy measurements confirmed the oxidation states and presence of Zn2+ , Ce4+ , Ce3+ and different bonded oxygen species in the nanocomposites. The prepared pure ZnO and CeO2 as well as the ZnO/CeO2 nanocomposites with various proportions of ZnO and CeO2 were tested for photocatalytic degradation of methyl orange, methylene blue and phenol under visible-light irradiation. The optimized and highly efficient ZnO/CeO2 (90:10) nanocomposite exhibited enhanced photocatalytic degradation performance for the degradation of methyl orange, methylene blue, and phenol as well as industrial textile effluent compared to ZnO, CeO2 and the other investigated nanocomposites. Moreover, the recycling results demonstrate that the ZnO/CeO2 (90:10) nanocomposite exhibited good stabili...

This paper presents a brief account of different technologies used for the treatment of petroleum refinery effluents (PRE). Broadly, PRE treatment is accomplished in two stages, namely, a series of pre-treatment steps, in which suspended matter, oil and grease are reduced, and an advanced stage, in which wastewater contaminants are decreased to certain acceptable discharge limits. Photocatalytic degradation techniques have been widely used in water and wastewater treatment. However, the literature regarding PRE treatment is scarce, and the technique is still not being utilised on an industrial scale in refineries. This is largely due to limited research findings discussing PRE treatments. Most researches are focused on treating singular contaminants found in PRE, e.g., phenols, sulphides, oil, grease and other organic components. This review focused on works that investigated PRE treatment by monitoring general refinery wastewater parameters, namely, chemical oxygen demand (COD), biological oxygen demand (BOD), total petroleum hydrocarbon (TPH), oil and grease (O&G), sulphate and phenols at the advanced treatment steps. This paper presents an overview of photocatalytic degradation and discusses published works with the goal of presenting the technique as an attractive and viable process unit. If optimised, this process has great potential for replacing other separation and degradation treatment approaches employed at the advanced treatment stage for PRE. © 2010 The Institution of Chemical Engineers.

http://ac.els-cdn.com/S0957582010001126/1-s2.0-S0957582010001126-main.pdf?_tid=ad24d2f2-2364-11e4-85bf-00000aab0f26&acdnat=1407987783_2679889d31a1d298d65dd23cc88a1a94 
http://www.sciencedirect.com/science/article/pii/S0957582010001126

... Basheer Hasan Diya'uddeen ∗ , Wan Mohd Ashri Wan Daud, AR Abdul Aziz ... ozone, H2O2, HOCl and chlorine, the oxidation potentials are 2.07, 1.78, 1.49, and 1.36, respectively (Al-Rasheed, 2005). ... This is achieved mechanically by gravity in API separators or separation tanks ...

NiS-SiO 2 and Cr 2 S 3-TiO 2 synthesized by Ultrasound-Microwave method was tested for the photo-degradation of methyl red as azo dye under ultraviolet (UV) light. The structure and morphology of the synthesized materials were examined through scanning electron microscopy, X-ray diffraction and photoelectron spectroscopy, energy-dispersive spectroscopy, dynamic light scattering and the band gap energy differences were determined through diffuse reflectance spectroscopy (DRS). The crystallite size and band gap values of SiO 2 , TiO 2 , NiS-SiO 2 and Cr 2 S 3-TiO 2-1 were obtained from XRD and UV-vis DRS analysis and found insignificant 44.22, 54.11, and 57.11 nm, and 8.9, 3.2, 3.0, 2.7 eV, respectively. The NiS-SiO 2 and Cr 2 S 3-TiO 2 nanocomposites exhibited good stability and catalytic performance in the azo dye degradation; the composite provides a complete degradation after 50 min under UV irradiation. The effects of different quencher compounds on the Methyl red dye degradation were also investigated. The result for this experiment shows the system without the quencher was highly degradation of Methyl red. The antibacterial influence of the SiO 2 , TiO 2 , NiS-SiO 2 and Cr 2 S 3-TiO 2-1 were studied versus two species bacteria. The antifungal performance of this nanoparticle was analyzed versus two species fungi as the C. albicans and P. funiculosum. Biological data demonstrated that the prepared catalyst has great bactericidal and fungicidal properties.