Journal articles: 'Recalcitrant photodegradation'

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Li, Xu Chun, Jun Ma, and Si Yang Yue. "Efficient Destruction of Chlorophenols by Ultraviolet Irradiation." Advanced Materials Research 476-478 (February 2012): 1955–59. http://dx.doi.org/10.4028/www.scientific.net/amr.476-478.1955.

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Chlorophenols (CPs), a group of recalcitrant and toxic pollutants, are widespread in the environment and threating human health. The environment-friendly technology, UV irradiation, could efficiently destruct CPs. The study investigated the influence of solution pH and positions and number of substituted chlorine atoms on photodegradation process of CPs, and also studied the photodegradation pathway. It found that the photodegradaton process of CPs was highly dependent on solution pH, and higher pH favored the degradation. The photodegradation processes agreed well with the pseudo-first order kinetics, and para- and ortho- positions and lower chlorination degree were more favorable for photodegradation of CPs. Most of the chlorine atoms were released as chloride ions, and suggest that the cleavage of the C-Cl bond occurred during the photodegradation process. It will provide some guidance for efficient treatment of CPs in water.

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Li, Xu Chun, Jun Ma, and Si Yang Yue. "Total and Efficient Removal of Tribromoacetic Acid by Ultraviolet Irradiation." Advanced Materials Research 518-523 (May 2012): 2939–43. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.2939.

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Tribromoacetic acid (TBAA), one of the typically recalcitrant and toxic chlorine disinfection byproducts (DBPs), is widespread in the drinking water and threating human health. The environment-friendly technology, UV irradiation, could efficiently destruct TBAA. The present study investigated the removal efficiency, photodegradation kinetics, and photodegradation mechanism of TBAA under UV irradiation. It revealed that the photodegradaton process of TBAA agreed well with the pseudo-first order kinetics, with the rate constant of 1.084 min-1and half-time of 0.64 minutes. Further study on intermediate products formation and mass balance indicated that complete debromination and detoxification were obtained with almost all the bromine atoms released as bromide ions, and suggest that the cleavage of three C-Br bonds concurrently occurred during the photolysis of one TBAA molecule. It will provide some guidance for efficient treatment of brominated contaminants in water.

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Toscanesi, Maria, Vincenzo Russo, Antonio Medici, Antonella Giarra, Maryam Hmoudah, Martino Di Serio, and Marco Trifuoggi. "Heterogeneous Photodegradation for the Abatement of Recalcitrant COD in Synthetic Tanning Wastewater." ChemEngineering 6, no. 2 (March 21, 2022): 25. http://dx.doi.org/10.3390/chemengineering6020025.

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Tannery wastewater is considered one of the most contaminated and problematic wastes since it consists of considerable amounts of organic and inorganic compounds. These contaminants result in high chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS). In this work, the heterogeneous photodegradation of recalcitrant COD in wastewater from the tanning industry was investigated, in particular the recalcitrant COD due to the presence of vegetable tannins extracted from mimosa and chestnut and from synthetic tannins based on 4,4′ dihydroxy phenyl sulfone. TiO2 Aeroxide P-25 was employed to study the photodegradation of model molecules in batch conditions under different parameters, namely initial concentration of COD, temperature, and catalyst dose. The maximum COD abatement reached was 60%. Additionally, preliminary kinetic investigation was conducted to derive the main kinetic parameters that can be useful for process scale-up. It was found to be independent of the temperature value but linearly dependent on both catalyst loading and the initial COD value.

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Loc, Luu Cam. "PERFORMANCE OF TiO2 IN PHOTODEGRADATION SEAFOOD WASTEWATER." Vietnam Journal of Science and Technology 54, no. 4B (March 22, 2018): 80. http://dx.doi.org/10.15625/2525-2518/54/4b/12027.

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In this work, photocatalysts TiO2-HT prepared by hydrothermal method and TiO2-P25 Degussa were characterized by Energy Dispersive X-Ray analysis (EDX), X-ray powder diffraction analysis (XRD), Raman Spectroscopy, BET surface area measurements, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and UV-Vis absorption spectroscopy and tested in degradation of recalcitrant organic pollutants in bio-treated seafood wastewater (COD > 80 mg/L). After 9 hours of photodegradation under UV-A irradiation, COD removal efficiency reached 85.6 % and 48.9 % on TiO2-P25 and TiO2 catalysts, respectively. COD values of seafood wastewater treated by photocatalysis met the standard discharge requirement - QCVN 11:2008 – level A (COD £ 50 mg/L).

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Serna-Galvis, Efraím A., Yudy L. Martínez-Mena, Jazmín Porras, Yenny Ávila-Torres, Javier Silva-Agredo, and Ricardo A. Torres-Palma. "Understanding the Role of Complexation of Fluoroquinolone and β-Lactam Antibiotics with Iron (III) on the Photodegradation under Solar Light and UVC Light." Water 13, no. 18 (September 21, 2021): 2603. http://dx.doi.org/10.3390/w13182603.

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Antibiotics elimination by some photochemical processes involves ferric ions, but little is discussed about the fundamental aspects of complexation effects on their degradation. This study compares the photodegradation of two fluoroquinolones, three β-lactams, and their ferric complexes in deionized water. The complexed antibiotics were more recalcitrant than the free antibiotics to the solar light action (the photodegradation rate constants diminished by more than 50%). To better study the photodegradation, other experiments considering two representative cases (ciprofloxacin and dicloxacillin) were performed. For ciprofloxacin, as the iron amount was increased from 0 to 7.5 µmol L−1, its photodegradation rate constant decreased from 0.017 to 0.004 min−1. In contrast, for dicloxacillin, the increase in iron concentration (from 0 to 7.5 µmol L−1) accelerated its photodegradation (the rate constant augmented from 0 to 0.0026 min−1). When UVC light was used, the degradations of free and complexed antibiotics were very close, exhibiting values of degradation rate constants between 0.030 and 0.085 min−1. The antimicrobial activity (AA) was eliminated when 90% of ciprofloxacin and 90–95% of dicloxacillin were degraded. The AA removal was associated with structural changes in relevant moieties of antibiotics, such as fluorine and piperazyl ring for ciprofloxacin, or β-lactam ring for dicloxacillin.

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Shen, Shuling, Di Wang, Mengmeng Jia, Shuning Xiao, Zhihong Tang, and Junhe Yang. "Ultrafast and high efficiency photodegradation of dyes under visible light by Au nanocluster-promoted Zn0.5Cd0.5S nanorods." CrystEngComm 23, no. 18 (2021): 3288–96. http://dx.doi.org/10.1039/d1ce00152c.

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Au nanoclusters decorated on the lateral surface of ultrathin ZCS nanorods could maximize the photocatalytic activity of ZCS by PRET mechanism. This makes it possible to use less photocatalysts to degrade more recalcitrant dyes in a short time.

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Alosaimi, Eid H., Nadia Azeem, Noor Tahir, Asim Jilani, Muhammad Zahid, Salman S. Alharthi, Javed Iqbal, Muhammad Yaseen, Zulfiqar Ahmad Rehan, and Imran Shahid. "Investigation of Fe-Doped Graphitic Carbon Nitride-Silver Tungstate as a Ternary Visible Light Active Photocatalyst." Journal of Chemistry 2021 (November 15, 2021): 1–18. http://dx.doi.org/10.1155/2021/4660423.

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The rapid population growth and economic development have largely contributed to environmental pollution. Various advanced oxidation processes have been used as the most viable solution for the reduction of recalcitrant pollutants and wastewater treatment. Heterogeneous photocatalysis is one of the broadly used technologies for wastewater treatment among all advanced oxidation processes. Graphitic carbon nitride alone or in combination with various other semiconductor metal oxide materials acts as a competent visible light active photocatalyst for the removal of recalcitrant organic pollutants from wastewater. Rational designing of an environment-friendly photocatalyst through a facile synthetic approach encounters various challenges in photocatalytic technologies dealing with semiconductor metal oxides. Doping in g-C3N4 and subsequent coupling with metal oxides have shown remarkable enhancement in the photodegradation activity of g-C3N4-based nanocomposites owing to the modulation in g-C3N4 bandgap structuring and surface area. In the current study, a novel ternary Fe-doped g-C3N4/Ag2WO4 visible light active photocatalyst was fabricated through an ultrasonic-assisted facile hydrothermal method. Characterization analysis included SEM analysis, FTIR, XRD, XPS, and UV-Visible techniques to elucidate the morphology and chemical structuring of the as-prepared heterostructure. The bandgap energies were assessed using the Tauc plot. The ternary nanocomposite (Fe-CN-AW) showed increased photodegradation efficiency (97%) within 120 minutes, at optimal conditions of pH = 8, catalyst dose = 50 mg/100 ml, an initial RhB concentration of 10 ppm, and oxidant dose 5 mM under sunlight irradiation. The enhanced photodegradation of rhodamine B dye by ternary Fe-CN-AW was credited to multielectron transfer pathways due to insertion of a Fe dopant in graphitic carbon nitride and subsequent coupling with silver tungstate. The data were statistically assessed by the response surface methodology.

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K., Alamelu, and Jaffar Ali B.M. "TiO2-Pt composite photocatalyst for photodegradation and chemical reduction of recalcitrant organic pollutants." Journal of Environmental Chemical Engineering 6, no. 5 (October 2018): 5720–31. http://dx.doi.org/10.1016/j.jece.2018.08.042.

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Vione, Davide. "Insights into the Time Evolution of Slowly Photodegrading Contaminants." Molecules 26, no. 17 (August 28, 2021): 5223. http://dx.doi.org/10.3390/molecules26175223.

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Photochemical degradation plays an important role in the attenuation of many recalcitrant pollutants in surface freshwaters. Photoinduced transformation kinetics are strongly affected by environmental conditions, where sunlight irradiance plays the main role, followed by water depth and dissolved organic carbon (DOC). Apart from poorly predictable weather-related issues, fair-weather irradiance has a seasonal trend that results in the fastest photodegradation in June and the slowest in December (at least in temperate areas of the northern hemisphere). Pollutants that have first-order photochemical lifetimes longer than a week take more than one month to achieve 95% photodegradation. Consequently, they may experience quite different irradiance conditions as their photodegradation goes on. The relevant time trend can be approximated as a series of first-order kinetic tracts, each lasting for one month. The trend considerably departs from an overall exponential decay, if degradation takes long enough to encompass seasonally varying irradiance conditions. For instance, sunlight irradiance is higher in July than in April, but increasing irradiance after April and decreasing irradiance after July ensure that pollutants emitted in either month undergo degradation with very similar time trends in the first 3–4 months after emission. If photodegradation takes longer, pollutants emitted in July experience a considerable slowdown in photoreaction kinetics as winter is approached. Therefore, if pollutants are photostable enough that their photochemical time trend evolves over different seasons, degradation acquires some peculiar features than cannot be easily predicted from a mere analysis of lifetimes in the framework of simple first-order kinetics. Such features are here highlighted with a modelling approach, taking the case of carbamazepine as the main example. This contaminant is almost totally biorecalcitrant, and it is also quite resistant to photodegradation.

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Sun, Zhuqiu, In-Sun Kang, Qianyuan Wu, Jinying Xi, and Hongying Hu. "Biotoxicity of Water-Soluble UV Photodegradation Products for 10 Typical Gaseous VOCs." International Journal of Environmental Research and Public Health 15, no. 7 (July 18, 2018): 1520. http://dx.doi.org/10.3390/ijerph15071520.

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Ultraviolet (UV) photodegradation is increasingly applied to control volatile organic compounds (VOCs) due to its degradation capabilities for recalcitrant compounds. However, sometimes the UV photodegradation products are also toxic and can affect human health. Here, 10 VOCs at 150~200 ppm in air were treated using a laboratory-scale UV reactor with 185/254 nm irradiation, and the biotoxicity of their off-gas was studied by investigating their off-gas absorption solutions. The CO2 increase and VOC decrease were 39~128 ppm and 0~42 ppm, respectively, indicating that the VOCs and their products were mineralized in off-gas absorption solutions. The total organic carbon (TOC) of the absorption solutions are 4~20 mg∙L−1. Luminescent bacteria and Daphnia magna were used to detect the acute toxicity, and an umu assay was used to determine the genotoxic potential. Trichloroethylene showed a highest toxicity to luminescent bacteria, while chlorobenzene had the lowest toxicity. Water-soluble UV photodegradation products for styrene are very toxic to Daphnia magna. In the umu assay, the genotoxicities of off-gas absorption solutions of trichloroethylene, methylbenzene, ethyl acetate, butyl alcohol, and styrene were 51.26, 77.80, 86.89, 97.20, and 273.62 mg (4-NQO)·L−1 respectively. In addition, the analysis of the genotoxicity/TOC and intermediates products indicated that the off-gas absorption solutions of styrene, trichloroethylene, and butyl alcohol contain many highly toxic substances.

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Lindell, Måns J., H. Wilhelm Granéli, and Stefan Bertilsson. "Seasonal photoreactivity of dissolved organic matter from lakes with contrasting humic content." Canadian Journal of Fisheries and Aquatic Sciences 57, no. 5 (May 1, 2000): 875–85. http://dx.doi.org/10.1139/f00-016.

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We studied seasonal variability in photodegradation of dissolved organic carbon (DOC) resulting from artificial ultraviolet-A (UV-A) and UV-B irradiation. Water samples were taken approximately monthly from the surface layers of two oligotrophic lakes with contrasting humic content, situated in southern Sweden. Lake water was filter-sterilized (0.2 μm) and exposed to artificial UV radiation in quartz tubes. Potential DOC photodegradation, measured as a photoproduction of dissolved inorganic carbon (DIC) and oxalic, malonic, formic, and acetic acid in irradiated samples, was observed throughout the sampling period. In addition, exposure to UV radiation resulted in a decrease in DOC, absorbance, and humic substance fluorescence. The photoproduction of DIC and the low molecular weight (LMW) organic acids varied seasonally, being generally higher in winter and spring (December-May), while DOC appeared to become less photoreactive after the extensive exposure to solar radiation during summer. Production rates of both DIC and LMW organic acids were approximately eight times higher in the humic lake despite that the DOC concentration was only two times higher than in the clearwater lake. This is most probably due to the high input of allochthonous DOC and the resulting higher absorbance to DOC ratio in the humic system. Furthermore, the longer hydraulic residence time in the clearwater system could have resulted in an accumulation of residual DOC, recalcitrant to further photodegradation.

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C., Loc L. "APPLICATION OF TiO2–P25 IN THE PHOTODEGRADATION OF n–LAURYL DIETHANOLAMINE AND CINNAMIC ACID IN PRESENCE OF OXYGEN." Vietnam Journal of Science and Technology 55, no. 1B (March 23, 2018): 249. http://dx.doi.org/10.15625/2525-2518/55/1b/12116.

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In this paper, the activity of TiO2–P25 in the photodecomposition of recalcitrant organic compounds such as n–lauryl diethanolamine (n–LDA) and cinnamic acid (CA) solution in UV + BLED light in presence of oxygen was investigated and the optimum conditions of reaction were determined. With physicochemical characteristics such as anatase/rutile ratio of 80/20, the crystallite size of 23 nm, BET surface area of 43.6, the light absorption wavelength of 390 nm, band gap energy of 3.17 eV, and point of zero charge of 6.3, TiO2–P25 catalyst is able to photodecompose more than 95 % of LDA and CA after 90 minutes in presence of oxygen under irradiation of UV–B light.

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Braman, Tanner, Lydia Dolvin, Corey Thrasher, Hongmin Yu, Emma Q. Walhout, and Rachel E. O’Brien. "Fresh versus Photo-recalcitrant Secondary Organic Aerosol: Effects of Organic Mixtures on Aqueous Photodegradation of 4-Nitrophenol." Environmental Science & Technology Letters 7, no. 4 (March 6, 2020): 248–53. http://dx.doi.org/10.1021/acs.estlett.0c00177.

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Dias, Jeferson Almeida, Vera Lúcia Arantes, Alfeu Saraiva Ramos, Tania Regina Giraldi, Marília Zani Minucci, and Sylma Carvalho Maestrelli. "Photocatalytic Degradation of Rhodamine B Dye through Zinc Oxide Obtained by High Energy Milling." Materials Science Forum 881 (November 2016): 398–403. http://dx.doi.org/10.4028/www.scientific.net/msf.881.398.

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The heterogeneous photocatalysis has been developed to treatment of recalcitrant organic effluents such as the dyes. The chemical reactions occur on a semiconductor surface exposed to electromagnetic radiation. The objective of this study was evaluate the high energy milling as a mechanism to obtain fine powders of ZnO to utilization in photocatalysis. Raw ZnO was characterized by X-Ray diffraction, BET, sedigraph and Helium pycnometry and it was milled during four and ten hours in dry and wet media. The milled powders were characterized by X-Ray diffraction and they were evaluated in photocatalytic degradation of Rhodamine B dye. The results showed high purity of the powders before and after milling and the photocatalytic efficiency was function of processing conditions. The average half-life time for the dye varied between of 990.2 and 7.6 min wherein the powder obtained by four hours in dry media milling showed the best results of photodegradation.

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Zhang, Jinpeng, Xiaoping Chen, Qiaoshan Chen, Yunhui He, Min Pan, Guocheng Huang, and Jinhong Bi. "Insights into Photocatalytic Degradation Pathways and Mechanism of Tetracycline by an Efficient Z-Scheme NiFe-LDH/CTF-1 Heterojunction." Nanomaterials 12, no. 23 (November 22, 2022): 4111. http://dx.doi.org/10.3390/nano12234111.

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Photocatalysis offers a sustainable approach for recalcitrant organic pollutants degradation, yet it is still challenging to seek robust photocatalysts for application purposes. Herein, a novel NiFe layered double hydroxide (LDH)/covalent triazine framework (CTF-1) Z-scheme heterojunction photocatalyst was rationally designed for antibiotics degradation under visible light irradiation. The NiFe-LDH/CTF-1 nanocomposites were readily obtained via in situ loading of NiFe-LDH on CTF-1 through covalent linking. The abundant coupling interfaces between two semiconductor counterparts lay the foundation for the formation of Z-scheme heterostructure, thereby effectively promoting the transfer of photogenerated electrons, inhibiting the recombination of carriers, as well as conferring the nanocomposites with stronger redox ability. Consequently, the optimal photocatalytic activity of the LDH/CTF heterojunction was significantly boosted for the degradation of a typical antibiotic, tetracycline (TC). Additionally, the photodegradation process and the mineralization of TC were further elucidated. These results envision that the LDH/CTF-1 can be a viable photocatalyst for long-term and sustainable wastewater treatment.

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Sánchez, Marta, Isabel Ruiz, and Manuel Soto. "The Potential of Constructed Wetland Systems and Photodegradation Processes for the Removal of Emerging Contaminants—A Review." Environments 9, no. 9 (September 6, 2022): 116. http://dx.doi.org/10.3390/environments9090116.

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The presence of emerging organic contaminants (EOCs) in the environment is increasing and requires the development of technologies for their effective removal. Therefore, a literature review on the behavior of EOCs during municipal wastewater treatment, both in major treatment systems and particularly in constructed wetlands (CWs), was carried out. The study also reviewed the behavior of EOCs in anaerobic digesters (ADs) and advanced oxidation processes, particularly in TiO2-based photocatalysis, which are being proposed as promising pre- and post-treatments for combination with CW. The following ten compounds were screened: acetaminophen (ACE), ofloxacin (OFL), caffeine (CAF), carbamazepine (CBZ), ketoprofen (KET), ibuprofen (IBU), diclofenac (DCL), clofibric acid (ACB), bisphenol A (BPA), and sotalol (SOT). The degradation pathways of the selected EOCs are largely influenced by their physicochemical and biochemical properties. Sorption and biodegradation are the main elimination mechanisms found in AD and CW treatment systems, where the combination of anaerobic and aerobic environments improves the elimination efficiency of EOCs. However, various contaminants appear recalcitrant. In this sense, in combination with CWs, TiO2-based photocatalysis emerges as a promising post-treatment for advanced EOC removal from wastewater.

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Ruiz-Flores, Alberto, Araceli García, Antonio Pineda, María Brox, Andrés Gersnoviez, and Eduardo Cañete-Carmona. "Low-Cost Photoreactor to Monitor Wastewater Pollutant Decomposition." Sensors 23, no. 2 (January 10, 2023): 775. http://dx.doi.org/10.3390/s23020775.

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Actually, the quality of water is one of the most important indicators of the human environmental impact, the control of which is crucial to avoiding irreversible damage in the future. Nowadays, in parallel to the growth of the chemical industry, new chemical compounds have been developed, such as dyes and medicines. The increasing use of these products has led to the appearance of recalcitrant pollutants in industrial wastewater, and even in the drinking water circuit of our populations. The current work presents a photoreactor prototype that allows the performance of experiments for the decomposition of coloured pollutants using photocatalysis at the laboratory scale. The design of this device included the study of the photometric technique for light emission and the development of a software that allows monitoring the dye degradation process. Open-source hardware platforms, such as Arduino, were used for the monitoring system, which have the advantages of being low-cost platforms. A software application that manages the communication of the reactor with the computer and graphically displays the data read by the sensor was also developed. The results obtained demonstrated that this device can accelerate the photodegradation reaction in addition to monitoring the changes throughout the process.

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Mezzina, Lidia, Angelo Nicosia, Fabiana Vento, Guido De Guidi, and Placido Giuseppe Mineo. "Photosensitized Thermoplastic Nano-Photocatalysts Active in the Visible Light Range for Potential Applications Inside Extraterrestrial Facilities." Nanomaterials 12, no. 6 (March 17, 2022): 996. http://dx.doi.org/10.3390/nano12060996.

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Among different depollution methods, photocatalysis activated by solar light is promising for terrestrial outdoor applications. However, its use in underground structures and/or microgravity environments (e.g., extraterrestrial structures) is forbidden. In these cases, there are issues related to the energy emitted from the indoor lighting system because it is not high enough to promote the photocatalytic mechanism. Moreover, microgravity does not allow the recovery of the photocatalytic slurry from the depolluted solution. In this work, the synthesis of a filmable nanocomposite based on semiconductor nanoparticles supported by photosensitized copolyacrylates was performed through a bulk in situ radical copolymerization involving a photosensitizer macromonomer. The macromonomer and the nanocomposites were characterized through UV-Vis, fluorescence and NMR spectroscopies, gel permeation chromatography and thermogravimetric analysis. The photocatalytic activity of the sensitized nanocomposites was studied through photodegradation tests of common dyes and recalcitrant xenobiotic pollutants, employing UV-Vis and visible range (λ > 390 nm) light radiations. The sensitized nanocomposite photocatalytic performances increased about two times that of the unsensitized nanocomposite and that of visible range light radiation alone (>390 nm). The experimental data have shown that these new systems, applied as thin films, have the potential for use in indoor deep underground and extraterrestrial structures.

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Guimarães, Vanessa, Ana R. Teixeira, Marco S. Lucas, and José A. Peres. "Effect of Zr Impregnation on Clay-Based Materials for H2O2-Assisted Photocatalytic Wet Oxidation of Winery Wastewater." Water 12, no. 12 (December 2, 2020): 3387. http://dx.doi.org/10.3390/w12123387.

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UV-activated Zr-doped composites were successfully produced through the impregnation of Zr on the crystal lattice of different clay materials by a one-step route. Fixing the amount of Zr available for dopage (4%), the influence of different supports, submitted to different chemical treatments, on the photocatalytic activity of the resulting Zr-doped pillared clay materials (PILC) was assessed. Both chemical characterization and structural characterization suggest that the immobilization of Zr on montmorillonite and PILC structures occurred through isomorphic substitution between Si and Zr in the tetrahedral sheet of the clay material. This structural change was demonstrated by significant modifications on Si-OH stretching vibrations (1016 cm−1, 1100 cm−1 and 1150 cm−1), and resulted in improved textural properties, with an increase in surface area from 8 m2/g (natural montmorillonite) to 107 m2/g after the pillaring process, and to 118 m2/g after the pillaring and Zr-doping processes ((Zr)Al-Cu-PILC). These materials were tested in the UV-photodegradation of agro-industrial wastewater (AIW), characterized by high concentrations of recalcitrant contaminants. After Zr-dopage on AlCu-PILC heterogeneous catalyst, the total organic carbon (TOC) removals of 8.9% and 10.4% were obtained through adsorption and 77% and 86% by photocatalytic oxidation, at pH 4 and 7, respectively. These results suggest a synergetic effect deriving from the combination of Zr and Cu on the photocatalytic degradation process.

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Ahsan, Hajra, Muhammad Shahid, Muhammad Imran, Faisal Mahmood, Muhammad Hussnain Siddique, Hayssam M. Ali, Muhammad B. K. Niazi, et al. "Photocatalysis and adsorption kinetics of azo dyes by nanoparticles of nickel oxide and copper oxide and their nanocomposite in an aqueous medium." PeerJ 10 (November 14, 2022): e14358. http://dx.doi.org/10.7717/peerj.14358.

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Background Azo dyes are recalcitrant organic pollutants present in textile industry effluents. Conventional treatment methods to remove them come with a range of disadvantages. Nanoparticles and their nanocomposites offer more efficient, less expensive and easy to handle wastewater treatment alternative. Methods In this study, nanoparticles of nickel oxide (NiO-NPs), copper oxide (CuO-NPs) and their nanocomposite (NiO/CuO-NC) were synthesized using co-precipitation method. The functional groups present on the surface of synthesized nanomaterials were verified using Fourier-transform infrared spectroscopy (FTIR). Surface morphology was assessed using scanning electron microscopy (SEM) whereas purity, shape and size of the crystallite were determined using X-ray diffraction (XRD) technique. The potential of these nanomaterials to degrade three dyes i.e., Reactive Red-2 (RR-2), Reactive Black-5 (RB-5) and Orange II sodium salt (OII) azo dyes, was determined in an aqueous medium under visible light (photocatalysis). The photodegradation effectiveness of all nanomaterials was evaluated under different factors like nanomaterial dose (0.02–0.1 g 10 mL−1), concentration of dyes (20–100 mg L−1), and irradiation time (60–120 min). They were also assessed for their potential to adsorb RR-2 and OII dyes. Results Results revealed that at optimum concentration (60 mgL−1) of RR-2, RB-5, and OII dyes, NiO-NPs degraded 90, 82 and 83%, CuO-NPs degraded 49, 34, and 44%, whereas the nanocomposite NiO/CuO-NC degraded 92, 93, and 96% of the said dyes respectively. The nanomaterials were categorized as the efficient degraders of the dyes in the order: NiO/CuO-NC > NiO-NPs > CuO-NPs. The highest degradation potential shown by the nanocomposite was attributed to its large surface area, small particles size, and quick reactions which were proved by advance analytical techniques. The equilibrium and kinetic adsorption of RR-2 and OII on NiO-NPs, CuO-NPs, and NiO/CuO-NC were well explained with Langmuir and Pseudo second order model, respectively (R2 ≥ 0.96). The maximum RR-2 adsorption (103 mg/g) was obtained with NiO/CuO-NC. It is concluded that nanocomposites are more efficient and promising for the dyes degradation from industrial wastewater as compared with dyes adsorption onto individual NPs. Thus, the nanocomposite NiO/CuO-NC can be an excellent candidate for photodegradation as well as the adsorption of the dyes in aqueous media.

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Hussain, Syed M., Tabassum Hussain, Moeen Faryad, Qasim Ali, Shafaqat Ali, Muhammad Rizwan, Abdullah I. Hussain, Madhumita B. Ray, and Shahzad A. S. Chatha. "Emerging Aspects of Photo-catalysts (TiO2 & ZnO) Doped Zeolites and Advanced Oxidation Processes for Degradation of Azo Dyes: A Review." Current Analytical Chemistry 17, no. 1 (December 30, 2020): 82–97. http://dx.doi.org/10.2174/1573411016999200711143225.

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Background: Azo dyes are recognized as non-decomposable and recalcitrant compounds and can be depleted into more dangerous secondary products in anaerobic environments. In the current scenario, different water treatment strategies, including adsorption, photocatalysis, and advanced oxidation processes based practices, are facing different limitations. Method: A literature survey was accomplished by searching the scientific data from different search engines, including Scopus, PubMed, Science Direct, Springer, Taylor and Francis, Google Scholar, Blackwell-Synergy, Wiley-Interscience and Research-Gate, etc. This article has been compiled after intensively reviewing about 231 research papers, reviews, and book chapters in the fields of industrial effluents, hazardous materials, and water treatment strategies with their advantages and limitations. Results: Molecular oxygen and other active species, such as O2•−, HO2•, H2O2, and •OH, play a significant role in the degradation of dyes in AOPs and photocatalyst utilizes sunlight energy and accelerates some chemical reactions depending upon the activation energies. Different reaction parameters, including calcination temperature, pH, initial dye concentration, and catalyst dosage, have a significant impact on photocatalytic degradation performance. Characterization of degradation processes of dye-stuffs could be carried out by the state-of-the-art analytical techniques i.e. UV-Visible spectroscopy, powdered XRD, FTIR (ATR), EDX-SEM, BET, and differential pulse voltammetry. GC-MS and LC-MS investigation of photodegradation by-products and intermediates could provide identification and possible degradation pathway for target dye molecules. This review covers research related to photocatalytic degradation of azo dyes by TiO2 and ZnO, widely used photocatalysts, and various combinations of zeolites. Conclusion: It can be concluded that the combination of nano-sorbents (Fly Ash Zeolites) and photocatalysts not only enhances the degradation but also effectively removes toxic dye molecules and their by-products. The review explains the suitability of synergic applications of catalysts (TiO2, ZnO) and catalytic bed (zeolites) for different industrial effluents and waste water treatment at a significant pace towards green technology.

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Rontani, J. F., B. Charriere, A. Forest, S. Heussner, F. Vaultier, M. Petit, N. Delsaut, L. Fortier, and R. Sempéré. "Intense photooxidative degradation of planktonic and bacterial lipids in sinking particles collected with sediment traps across the Canadian Beaufort Shelf (Arctic Ocean)." Biogeosciences Discussions 9, no. 6 (June 26, 2012): 7743–81. http://dx.doi.org/10.5194/bgd-9-7743-2012.

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Abstract. The lipid content of seven samples of sinking particles collected with sediment traps moored at ~100 m depth in summer and fall across the Canadian Beaufort Shelf (Arctic Ocean) was investigated. Our main goal was to quantify and characterize the biotic and abiotic degradation processes that acted on sinking material during these periods. Diatoms, which dominated the phytoplanktonic assemblage in every trap sample, appeared to be remarkably sensitive to Type II (i.e. involving singlet oxygen) photodegradation processes in summer, but seemed to be relatively unaffected by biotic degradation at the same time. Hence, the relative recalcitrance of phytodetritus towards biodegradation processes during the Arctic midnight sun period was attributed to the strong photodegradation state of heterotrophic bacteria, which likely resulted from the efficient transfer of singlet oxygen from photodegraded phytoplanktonic cells to attached bacteria. In addition, the detection in trap samples of photoproducts specific to wax ester components found in herbivorous copepods demonstrated that zooplanktonic faecal material exported out of the euphotic zone in summer were as well affected by Type II photodegradation processes. By contrast, sinking particles collected during the autumn were not influenced by any light-driven stress. Further chemical analyses showed that photodegraded sinking particles contained an important amount of intact hydroperoxides, which could then induce a strong oxidative stress in underlying sediments.

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Rontani, J. F., B. Charriere, A. Forest, S. Heussner, F. Vaultier, M. Petit, N. Delsaut, L. Fortier, and R. Sempéré. "Intense photooxidative degradation of planktonic and bacterial lipids in sinking particles collected with sediment traps across the Canadian Beaufort Shelf (Arctic Ocean)." Biogeosciences 9, no. 11 (November 23, 2012): 4787–802. http://dx.doi.org/10.5194/bg-9-4787-2012.

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Abstract. The lipid content of seven samples of sinking particles collected with sediment traps moored at ~ 100 m depth in summer and fall across the Canadian Beaufort Shelf (Arctic Ocean) was investigated. Our main goal was to quantify and characterize the biotic and abiotic degradation processes that acted on sinking material during these periods. Diatoms, which dominated the phytoplanktonic assemblage in every trap sample, appeared to be remarkably sensitive to Type II (i.e. involving singlet oxygen) photodegradation processes in summer, but seemed to be relatively unaffected by biotic degradation at the same time. Hence, the relative recalcitrance of phytodetritus towards biodegradation processes during the Arctic midnight sun period was attributed to the strong photodegradation state of heterotrophic bacteria, which likely resulted from the efficient transfer of singlet oxygen from photodegraded phytoplanktonic cells to attached bacteria. In addition, the detection in trap samples of photoproducts specific to wax ester components found in herbivorous copepods demonstrated that zooplanktonic faecal material exported out of the euphotic zone in summer were affected by Type II photodegradation processes as well. By contrast, sinking particles collected during the autumn were not influenced by any light-driven stress. Further chemical analyses showed that photodegraded sinking particles contained an important amount of intact hydroperoxides, which could then induce a strong oxidative stress in underlying sediments.

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Su, Shouhua, Juan Wang, Chao Li, Jinfeng Yuan, Zhicheng Pan, and Mingwang Pan. "Short-Branched Fluorinated Polyurethane Coating Exhibiting Good Comprehensive Performance and Potential UV Degradation in Leather Waterproofing Modification." Coatings 11, no. 4 (March 30, 2021): 395. http://dx.doi.org/10.3390/coatings11040395.

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In the current leather market, waterproof leather occupies a large proportion, where waterproofness has become one of the important standards for leather selection. However, the most advanced fluorine-containing waterproofing agents on the market always have long chains of over eight carbons (C8), whose use has been restricted due to their bioaccumulation and recalcitrance in natural environment. Consequently, creating waterproof materials characterized by their environmentally friendly qualities and high performance is of great significance. Herein, we report a novel strategy for preparation of the fluorinated polyurethanes containing short branched fluorocarbon chains, and apply it in leather waterproofing. Because the fluorine-containing chain segments are enriched on the coating surface, the waterproof agent coating shows good hydrophobicity, low water absorption, high wear resistance and potential photodegradation of performances. Additionally, the water and oil proof performances of the coating are comparable to that of the marketed C8 waterproofing agent. Its solvent-resistant and antifouling performances are also outstanding. Therefore, the coating can meet the property requirements for daily use and has broad application prospects.

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Tawfik, Ahmed, Mohamed Gar Alalm, Hanem M. Awad, Muhammad Islam, Muhammad Abdul Qyyum, Ala’a H. Al-Muhtaseb, Ahmed I. Osman, and Moonyong Lee. "Solar photo-oxidation of recalcitrant industrial wastewater: a review." Environmental Chemistry Letters, February 19, 2022. http://dx.doi.org/10.1007/s10311-022-01390-4.

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AbstractConventional methods to clean wastewater actually lead to incomplete treatments, calling for advanced technologies to degrade recalcitrant pollutants. Herein we review solar photo-oxidation to degrade the recalcitrant contaminants in industrial wastewater, with focus on photocatalysts, reactor design and the photo-Fenton process. We discuss limitations due to low visible-light absorption, catalyst collection and reusability, and production of toxic by-products. Photodegradation of refractory organics by solar light is controlled by pH, photocatalyst composition and bandgap, pollutant properties and concentration, irradiation type and intensity, catalyst loading, and the water matrix.

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Pretali, Luca, Elisa Fasani, and Michela Sturini. "Current advances on the photocatalytic degradation of fluoroquinolones: photoreaction mechanism and environmental application." Photochemical & Photobiological Sciences, April 13, 2022. http://dx.doi.org/10.1007/s43630-022-00217-z.

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AbstractHeterogeneous photocatalysis is one of the most studied and promising techniques for degradation of contaminants of emerging concern, especially pharmaceuticals, and it represents a potential application in wastewater treatment of recalcitrant pollutants, such as fluoroquinolones, which are almost not abated by standard WWTPs. Although photodegradation partially contributes to alleviate their accumulation into the aquatic systems, heterogeneous photocatalysis assures complete sequestration and mineralization of FQs and their photoproducts and offers many advantages with respect to the other advanced oxidation processes (AOPs). The present brief review summarizes the most recent studies regarding the development and application of novel photocatalytic materials to the removal of FQs from contaminated waters. The collected data are arranged relating the mechanistic aspects to specific catalysts’ properties, such as adsorption capacity, easy recovery, and reusability, especially under actual conditions. Graphical abstract

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Sun, Zhirong, Zhuowei Cheng, Pengfei Luo, Jianmeng Chen, Jianming Yu, Dongzhi Chen, and Peng Zhao. "Cyclohexane removal and UV post-control of bioaerosols in a combination of UV pretreatment and biotrickling filtration." Frontiers in Environmental Science 10 (September 28, 2022). http://dx.doi.org/10.3389/fenvs.2022.1010980.

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Biofiltration of hydrophobic and recalcitrant volatile organic compounds faces challenges, and the bioaerosols sourced from the biofiltration might cause secondary pollution. In this study, the combination of ultraviolet photodegradation and biotrickling filtration (UV-BTF) was designed to treat gaseous cyclohexane, and UV post-treatment (post-UV) was further utilized for the bioaerosol emissions management. Results showed that the combined UV-BTF permitted faster biofilm formation and had better removal efficiencies (REs) than the single biotrickling filter (BTF). The maximum elimination capacity (EC) of UV-BTF and single BTF was 4.4 and 1.32 g m−3 h−1, respectively. Carbon balance for the bioreactor showed that both BTF and UV-BTF could convert more than 50% of the initial cyclohexane into microbial biomass. High-throughput sequencing analysis showed that UV-BTF had a richer and more diverse microbial community compared with the single one. The post-UV had a good inactivation effect on the bioaerosols. Not solely the concentrations additionally the particle sizes of the bioaerosols from the post-UV became lower and smaller than those from the single BTF. Microbial analysis showed that UV had a greater impact on the species and quantity of both bacteria and fungi, but mainly on the number of bacteria. Such results suggested that UV could be used as the pretreatment for the enhancement of hydrophobic and recalcitrant VOCs removal in the subsequent biopurification, and also as the post-treatment for the inactivation of some harmful bioaerosols.

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De Souza, Danilo Rodrigues, Marcelo Galdino, and Letícia da Silva Lima. "Determination of the Heterogeneous Photodegradation Velocity Constant of Sodium Diclofenac with the Evaluation of Residual Toxicity in Artemia salina." Orbital: The Electronic Journal of Chemistry, December 27, 2022, 221–27. http://dx.doi.org/10.17807/orbital.v14i4.17652.

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With population growth and increasing urbanization, pollution of aquatic matrices has become frequent, with many studies focused on emerging contaminants as they are recalcitrant and bioaccumulative substances. With the deficiency in conventional water and sewage treatments, this work seeks alternatives for the mitigation of these pollutants, proposing the role of heterogeneous photocatalysis in the degradation of drugs, in this case, sodium diclofenac (SDF). Photocatalytic tests were performed using a bench system. The samples obtained were quantified using a colorimetric method with the aid of a UV-Vis spectrophotometer. The main observation was intense and rapid degradation of the drug in the first 10 min, indicating a reduction in the concentration of 71.05%. For the periods of 0-10 min and 10-60 min, two photodegradation regimes were estimated, with the first regime having an apparent rate constant of 0.12394 min-1 and the second of 0.01601 min-1. Toxicity bioassays were performed with the aid of Artemia salina, determining a 50% lethal concentration of 4.45 x 10-4 molL-1. When performing a new photocatalysis to determine the toxicity of the waste generated it was possible to observe a significant decrease in toxicity in the first 30 min, reaching a total reduction in 120 min.

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Journal articles on the topic 'Recalcitrant photodegradation'

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