Photo-oxidation Of Organic Pollutants Research Articles

Synergistic enhancement of simazine degradation using ZnO nanosheets and ZnO/GO nanocomposites: A sol-gel synthesis approach

This study aims to optimize the synergistic effect in photocatalytic processes by facilitating the accumulation of graphene oxide (GO) layers onto ZnO nanoparticles, thereby achieving close contact between the two materials, leveraging the high surface-to-volume ratio and efficient charge transport pathways inherent in ZnO nanosheets. The performance of ZnO nanosheets in the photocatalytic degradation of Simazine was investigated, with the aim of further enhancing the performance of the best-performing sample through GO decoration. Accordingly, ZnO nanosheets were obtained by the sol-gel method using different concentration of zinc acetate hexahydrate as a zinc source. According to the obtained results, it was observed that the sample prepared with a concentration of 0.44 M zinc precursor salt exhibited the best performance with a degradation rate of 67 %. In order to improve the performance of the sample prepared under this condition, graphene oxide (GO) was integrated into ZnO nanosheets to form a ZnO/GO nanocomposite structure. This composite structure achieved a photodegradation efficiency of 85 % for Simazine. The data obtained showed that the use of GO-based ZnO nanocomposites can improve charge separation, light absorption, charge transport and photo-oxidation of organic pollutants.

REVIEW OF THERMODYNAMIC AND PHYSICO-CHEMICAL PARAMETERS INFLUENCING METHYLENE BLUE ADSORPTION ON ACTIVATED CHARCOAL OF NATURAL ORIGIN

Methylene blue (MB) is a phenothiazine derivative used in microbiology, surgery, diagnostics and as a sensitizer in the photo-oxidation of organic pollutants. These numerous uses of methylene blue could lead to its accumulation in wastewater, causing harmful effects on the environment and living beings. To combat these harmful effects, numerous wastewater treatment processes, particularly physicochemical, were implemented. Adsorption techniques are particularly used to find new natural, biodegradable and inexpensive adsorbents to treat colored waste from structures such as medical and pharmaceutical laboratories. The aim of the present study was to carry out a relevant bibliographical review of the physico-chemical and thermodynamic parameters that can influence this adsorption of methylene blue on activated carbons of natural origin. The results showed a remarkable elimination of methylene blue. However, parameters such as particle size, adsorbent mass, pH, contact time, initial methylene blue concentration, agitation speed and temperature showed that the adsorption capacity of MB on biosorbents was influenced by these quantities. Similarly, the positive and negative enthalpy values (ΔH°) indicated that adsorption process could be endothermic or exothermic. Other thermodynamic parameters, such as the negative value of Gibbs free energy (ΔG°) and the positive value of entropy (ΔS°), also showed that the adsorption process was feasible and spontaneous.

Synthesis, Characterization, and Photocatalytic Activities of Graphene Oxide/metal Oxides Nanocomposites: A Review.

Sustainable water processing techniques have been extensively investigated and are capable of improving water quality. Among the techniques, photocatalytic technology has shown great potential in recent years as a low cost, environmentally friendly and sustainable technology. However, the major challenge in the industrial development of photocatalyst technology is to develop an ideal photocatalyst which must have high photocatalytic activity, a large specific surface area, harvest sunlight and shows recyclability. Keeping these views, the present review highlighted the synthesis approaches of graphene/metal oxide nanocomposite, characterization techniques and their prominent applications in photocatalysis. Various parameters such as photocatalyst loading, structure of photocatalyst, temperature, pH, effect of oxidizing species and wavelength of light were addressed which could affect the rate of degradation. Moreover, the formation of intermediates during photo-oxidation of organic pollutants using these photocatalysts is also discussed. The analysis concluded with a synopsis of the importance of graphene-based materials in pollutant removal. Finally, a brief overview of the problems and future approaches in the field is also presented.

Photo-Oxidation of Bisphenol A in Aqueous Solutions at Near Neutral pH by a Fe(III)-Carboxylate Complex with Oxalacetic Acid as a Benign Molecule.

The photo-oxidation of organic pollutants as induced by ferric-carboxylate complexes was known to be a photo-Fenton-like process. The use of a carboxylate ligand with higher efficiency and lower toxicity at near neutral pH is of high interest to researchers. In this work, photo-oxidation of bisphenol A (BPA) induced by a ferric-oxalacetic acid complex in aqueous solutions was investigated under 395 nm LED lamps. The results showed that the rate of BPA degradation increased in the order pH 10.0 << 8.0 < 6.5 < 4.0 within the first 10 min. More than 90% of BPA was successfully oxidized with Fe(III)/oxalacetic acid with a ratio of 1:5 at pH 6.5, which was primarily attributed to the generated hydroxyl radical. Iron in the Fe(III)-oxalacetic acid system was reused by simple addition of oxalacetic acid to the reaction mixture. Compared to common carboxylate ligands (pyruvic acid, oxalic acid, and citric acid), oxalacetic acid is more efficient and environmentally friendly for the Fe(III)-carboxylate complex-based photo-Fenton-like process at near neutral pH.

Pt/TiO2 Coupled with Water-Splitting Catalyst for Organic Pollutant Photodegradation: Insight into the Primary Reaction Mechanism

A composited system was fabricated by coupling Pt/TiO2 with water-splitting catalyst for photooxidation of organic pollutants in aqueous solutions. The new composited system exhibits more efficient photocatalytic activity than pure Pt/TiO2 does under UV light irradiation. The promoting effect is dependent on the photo-produced H2 over the composited system. The active oxygen species, hydroxyl radical (·OH) and hydrogen peroxide (H2O2), are measured by fluorescence spectroscopy and photometric method, respectively. The results reveal that the produced H2 by photocatalytic water splitting over NiO/NaTaO3:La transfers to Pt particle of TiO2 surface, then reacts with introducing O2 to generate in situ intermediate H2O2, and finally translates into ·OH radical to accelerate the photooxidation of organic pollutants.

Sunlight Photooxidation of Organic Pollutants in Wastewater

The material presented represents results of a research on a new method for using solar energy for municipal and industrial wastewater treatment. This research seeks to develop economical methods of disinfection and detoxification of wastewaters which would result in the reuse of effluents for crop irrigation. Aerated effluents containing dye-sensitizers were exposed to solar irradiation for various periods of time. The influence of the solar energy, absorbed by these sensitizers in the visible range, on the organic matter and anionic surfactants in secondary effluents was checked by determining the COD and MBAS values of treated wastewater. The disinfection potential of this method was followed by bacteriological analyses of running water or secondary effluents, previously contaminated or enriched, respectively, with laboratory cultures of E. coli, bacteriophages (coliphage X and F2) and polio virus (type L-Sc 1). The influence of this photooxidative method was also studied in eutrophic algae present in the Lake of Galilee. It was found that the conditions under which disinfection proceeds also support algicidal processes, causing lethal damage to algal cultures. Further investigations on stable pesticides (uracil, s-triazine and anilide derivatives) in surface water or industrial wastewater showed that such a method can also be used for detoxifying pesticides in these waters.