Photocatalytic Advanced Oxidation Processes Research Articles

Catalyst-On-Hotspot Nanoarchitecture: Plasmonic Focusing of Light onto Co-Photocatalyst for Efficient Light-To-Chemical Transformation.

Plasmon-mediated catalysis utilizing hybrid photocatalytic ensembles promises effective light-to-chemical transformation, but current approaches suffer from weak electromagnetic field enhancements from polycrystalline and isotropic plasmonic nanoparticles as well as poor utilization of precious co-catalyst. Here, efficient plasmon-mediated catalysis is achieved by introducing a unique catalyst-on-hotspot nanoarchitecture obtained through the strategic positioning of co-photocatalyst onto plasmonic hotspots to concentrate light energy directly at the point-of-reaction. Using environmental remediation as a proof-of-concept application, the catalyst-on-hotspot design (edge-AgOcta@Cu2 O) enhances photocatalytic advanced oxidation processes to achieve superior organic-pollutant degradation at ≈81% albeit having lesser Cu2 O co-photocatalyst than the fully deposited design (full-AgOcta@Cu2 O). Mass-normalized rate constants of edge-AgOcta@Cu2 O reveal up to 20-fold and 3-fold more efficient utilization of Cu2 O and Ag nanoparticles, respectively, compared to full-AgOcta@Cu2 O and standalone catalysts. Moreover, this design also exhibits catalytic performance >4-fold better than emerging hybrid photocatalytic platforms. Mechanistic studies unveil that the light-concentrating effect facilitated by the dense electromagnetic hotspots is crucial to promote the generation and utilization of energetic photocarriers for enhanced catalysis. By enabling the plasmonic focusing of light onto co-photocatalyst at the single-particle level, the unprecedented design offers valuable insights in enhancing light-driven chemical reactions and realizing efficient energy/catalyst utilizations for diverse chemical, environmental, and energy applications.

Deactivation of porphyrin metal-organic framework in advanced oxidation process: Photobleaching and underlying mechanism

Porphyrin metal-organic frameworks (MOFs) are widely used in photocatalytic advanced oxidation processes (AOP). However, the stability and deactivation of MOFs, crucial for reusability, have been understudied compared to their catalytic activity. We investigated photobleaching in porphyrin MOFs PCN-224-M (M= H2, Fe, Co, Cu, Zn) under visible light and H2O2. The MOFs exhibited crystallinity loss, ring-opening cleavage, and linker degradation. Photobleaching resulted from direct redox reactions between porphyrin sites and H2O2. Metal-oxo-porphyrin intermediates played a key role in the "group effect," with different functional groups affecting the photobleaching rate: PCN-224-Fe ≈ PCN-224-Co > PCN-224-H2 > PCN-224-Cu ≈ PCN-224-Zn. This trend related to chelated metal ions' electronic structures and their propensity for metal-oxo intermediate formation, establishing a structure-stability relationship. Our study enhances understanding of deactivation mechanisms in porphyrin MOFs during AOP, aiding the design of resilient and efficient MOF catalysts for environmental applications.

Comparative Study of Organics Removal from Refinery Wastewater by Photocatalytic Fenton Reaction Coupled with Visible Light and Ultraviolet Irradiation

The study investigates photocatalytic advanced oxidation processes using iron-doped zeolite catalysts in heterogeneous Fenton reactions to degrade organic contents as chemical oxygen demand. The research revealed that the heterogenous photocatalytic Fenton process was the most successful treatment method under acidic circumstances and generated a greater rate of chemical oxygen demand degradation in a concise amount of radiation time. Compared to the heterogenous Fenton process with ultraviolet irradiation, it increased oxidation and was affected by catalyst load, power of hydrogen pH, hydrogen peroxide amounts, and temperature. The findings showed that the iron-doped zeolite catalyst, pH, and temperature significantly degraded the chemical oxygen demand. The experiment determined that the optimal conditions were obtained at a catalyst load of 0.07 g, pH of 3, with 20% excess of hydrogen peroxide, 40 °C in 2 hours for the ultraviolet/ iron-doped zeolite/hydrogen peroxide system that gave 99.84 % of the removal of the chemical oxygen demand. The heterogeneous photocatalytic Fenton method accompanied the reactions by hydroxyl radical production, which quickly reached its maximal reduction.

Magnetically separable MnFeCoNiCu-based high entropy alloy nanoparticles for photocatalytic oxidation of antibiotic cocktails in different aqueous matrices

Destroying persistent organic pollutants via photocatalytic advanced oxidation processes is critical for sustainable water management. In spite of the tremendous progress in developing highly effective and durable photocatalysts in recent decades, inferior optical absorption and rapid charge recombination considerably restrict their application on a commercial scale. In order to address these issues, herein we have constructed MnFeCoNiCu-based high entropy alloy (HEA) nanoparticles (NPs), through a facile and straightforward procedure, and showcase its superiority over conventional photocatalysts in degrading some typical antibiotics (viz., sulfamethoxazole, SMX; ofloxacin, OFX; and ciprofloxacin, CFX). The equimolar HEA-NPs feature n-type semiconducting properties, improved light trapping ability, and reduced charge recombination. Consequently, a high degradation of 95 %, 94 %, and 89 % for SMX, OFX, and CFX, respectively, can be achieved in the presence of MnFeCoNiCu NPs under visible light illumination, without any serious risks of secondary contamination. In order to better evaluate the photocatalytic performance of MnFeCoNiCu NPs, particularly from a practical perspective, the removal of antibiotic pollutants from multicomponent systems is also investigated. The average treatment efficiency for a ternary mixture of SMX, OFX, and CFX in different aqueous matrices decreases in the order of deionized water (∼82 %) < tap water (∼86 %) < river water (∼78 %) < hospital wastewater (∼60 %) < domestic wastewater (∼57 %) < pharmaceutical industry wastewater (∼47 %). Further, the expended HEA-NPs can be conveniently recovered from the reaction system by applying an external magnetic field, allowing recurrent usage, without any substantial alteration in their microstructure and performance. These demonstrations of satisfactory photocatalytic activity under a diverse spread of realistic environmental conditions, excellent durability, and inexpensive retrieval endorse the application potential of MnFeCoNiCu NPs in decentralized water treatment systems.

Fenton and photo-assisted advanced oxidative degradation of ionic liquids: a review.

Ionic liquids (ILs) are the class of materials which are purely ionic in nature and liquid at room temperature. Their remarkable properties like very low vapour pressure, non-inflammable and high heat resistance are responsible for their use as a very appealing solvent in a variety of industrial applications in place of regular organic solvents. Because ILs are water soluble to a certain extent, the industrial wastewater effluents are found to contaminate with their traces. The non-biodegradability of ILs attracts the attention of the researchers for their removal or degradation from wastewater. Numbers of methods are available for the treatment of wastewater. However, it is very crucial to use the most efficient method for the degradation of ILs. Advanced oxidation process (AOP) is one of the most important techniques for the treatment of ILs in wastewater which have been investigated during last decades. This review paper covers the cost-effective Fenton, photochemical and photocatalytic AOPs and their combination that could be applied for the degradation of ILs from the wastewater. Theoretical explanations of these AOPs along with experimental conditions and kinetics of degradation or removal of ILs from water and wastewater have been reported and compared. Finally, future perspectives of IL degradation are presented.

Induced defect and ZnO nano-flower formation by N, N, dimethylformamide solvent for natural sunlight responsive floating photocatalytic advanced oxidation process

The increasing disposal of dyes and face-mask propel to hunt for a solution to fight water pollution while assisting sustainability. This research overcomes the key challenges associated with implementing photocatalytic water treatment by using natural sunlight active photocatalyst, changing slurry system, eliminating the use of external triggering sources, and reusing face-mask fabric coated with ZnO to act as a floating photocatalyst. Unique morphological structures-cauliflower, hydrangea, and petals-likes are obtained with the variation in synthesis medium (Diethylene glycol (DEG), N, N-dimethyl formamide (DMF), H2O) and methods (precipitation, solvothermal) which are found to be dependent on the solvent properties. With the use of DMF having a higher dielectric constant and formation of dimethyl amine via hydrolysis, it influences in forming petals and flower-like morphologies, unlike DEG solvent. The ZnO-coated face-mask fabric is used as the floating photocatalyst under natural sunlight observing comparable 91% degradation efficiency in 100 min with that of 99% efficiency in the UV light-illuminated slurry system. The formation of petals-like structures, defects from the liberation of DMF molecules from the ZnO surface by calcination, larger pore sizes and pore volumes provided a synergistic effect on enhancing the degradation efficiency in these cases.

Microwave-Assisted Photocatalytic Degradation of Organic Pollutants via CNTs/TiO2

Introducing microwave fields into photocatalytic technology is a promising strategy to suppress the recombination of photogenerated charge carriers. Here, a series of microwave-absorbing photocatalysts, xCNTs/TiO2, were prepared by combining titanium dioxide (TiO2) with carbon nanotubes (CNTs) using a typical alcoholic thermal method to study the promotion of microwave-generated thermal and athermal effects on the photocatalytic oxidation process. As good carriers that are capable of absorbing microwaves and conducting electrons, CNTs can form hot spots and defects under the action of the thermal effect from microwaves to capture electrons generated on the surface of TiO2 and enhance the separation efficiency of photogenerated electrons (e−) and holes (h+). Excluding the influence of the reaction temperature, the athermal effect of the microwave field had a polarizing effect on the catalyst, which improved the light absorption rate of the catalyst. Moreover, microwave radiation also promoted the activation of oxygen molecules and hydroxyl groups on the catalyst surface to generate more reactive oxygen radicals. According to the mechanism analysis, the microwave effect significantly improved the photocatalytic advanced oxidation process, which lays a solid theoretical foundation for practical application.

Accelerated activation of H2O2 and persulfate by Sm-doped ZnO@highly-defective layered yttria nanocomposite under visible-light irradiation for dyeing wastewater treatment: Comprehensive dominance of oxygen vacancies in photocatalytic advanced oxidation processes

Herein, innovative visible-light-driven nano-photocatalysts for accelerated-activation of H2O2 and persulfate (PS) are explored towards degradation of ionic-dyes from wastewater. Highly-defective yttria-layers (D-Y2O3) are customized and used for stabilization of ZnO and Sm-doped ZnO (Sm-ZnO) nanoparticles. Comparing to ZnO@D-Y2O3, Sm-ZnO@D-Y2O3 nanocomposite possesses advanced surface-area and porosity with significant surface-heterogeneity, elevated negatively-charged nanoparticles (ζav = −36.3 mV), large populations of oxygen vacancies, and enhanced visible-light absorptivity. PS-activation over visible-light-driven Sm-ZnO@D-Y2O3 photocatalyst (Sm-ZnO@D-Y2O3/PS/Vis) displays superior degradation efficiency (~100 %) of isosulfan-blue, Bismarck-brown, and methylene-blue dyes within 10 min, near-complete mineralization performance, and great cyclability. Such excellent photodegradability results from (i) synergistic combination of nanocomposite-PS-visible light, yielding highly-developed synergy-index values (SI = 3–20), (ii) abundant generation of reactive-oxidizing-species (SO4•-/h+/•OH synergistic ratio 1:1.8:1.9), and (iii) facilitated transference of photoexcited-electrons across oxygen vacancies in yttria-moiety, prohibiting electron-hole pairs recombination. Hence, Sm-ZnO@D-Y2O3/PS/Vis system is an extraordinarily candidate for complete destruction of organic-pollutants via newly photocatalytic-mechanism, whatever it treats it degrades.

Rapid Degradation of Rhodamine B through Visible-Photocatalytic Advanced Oxidation Using Self-Degradable Natural Perylene Quinone Derivatives-Hypocrellins.

Hypocrellins (HYPs) are natural perylene quinone derivatives from Ascomycota fungi. Based on the excellent photosensitization properties of HYPs, this work proposed a photocatalytic advanced oxidation process (PAOP) that uses HYPs to degrade rhodamine B (RhB) as a model organic pollutant. A synergistic activity of HYPs and H2O2 (0.18 mM of HYPs, 0.33% w/v of H2O2) was suggested, resulting in a yield of 82.4% for RhB degradation after 60 min under visible light irradiation at 470–475 nm. The principle of pseudo-first-order kinetics was used to describe the decomposition reaction with a calculated constant (k) of 0.02899 min−1 (R2 = 0.983). Light-induced self-degradation of HYPs could be activated under alkaline (pH > 7) conditions, promising HYPs as an advanced property to alleviate the current dilemma of secondary pollution by synthetic photocatalysts in the remediation of emerging organic pollutants.

Promotion of sulfameter degradation by coupling persulfate and photocatalytic advanced oxidation processes with Fe-doped MOFs

• Heterogeneous advanced oxidation and photocatalysis were coupled for degradation of sulfameter. • The absorption wavelength of UiO-66 material was extended to the visible region by Fe doping. • Fe-UiO-66 has a large specific surface area, which provides more active sites for the degradation reaction. • Photogenerated electron from photocatalysis processes can activate PS to generate SO 4 −• radicals. • Fe-UiO-66 can effectively improve the combination of photocatalytic technology and persulfate advanced oxidation technology. The metal–organic framework (MOF) UiO-66 was successfully doped with Fe via a facile solvothermal method. Fe-UiO-66 exhibited excellent solar photodegradation performance for sulfonamide antibiotics in water. The degradation rate of sulfameter by Fe-UiO-66 was 89.9% within 300 min under visible light, which confirmed the energy-saving and environmentally friendly properties of the material. Fe doping effectively improved the catalytic activity and reaction efficiency of Fe-UiO-66 by coupling photocatalysis with persulfate-based advanced oxidation. The favorable photocatalytic performance was mainly due to the introduction of Fe, which caused UiO-66 to extend into the solar range. In addition, quenching analysis confirmed that SO 4 2− and O 2 − free radicals played a more prominent role than OH and h + . Furthermore, sulfonamide antibiotics were successfully degraded under sunlight. Thus, Fe-based materials have substantial potential for the removal of antibiotic pollutants from wastewater.

Cu-MOF for effectively organic pollutants degradation and E. coli inactivation via catalytic activation of peroxymonosulfate

BackgroundThe Fenton-like reaction is a highly potential advanced oxidation process. The photo-Fenton-like reaction formed by the combination of photocatalytic advanced oxidation process, which combines their advantages, breaks the original Fenton-like reaction rate bottleneck. MethodsIn this study, an ultra-thin MOF (Cu-TCPP(BA)-MOF) with porphyrin as the ligand and copper as the metal node was synthesized via a simple one-pot method for the first time. Significant FindingsIt activates Peroxymonosulfate (PMS) under visible light to degrade 10 mg/L Rhodamine B which can be completely degraded within 40 min. The pseudo-first-order rate constant of RhB is 0.9011 min−1, being 5 folds larger than this for CuO as catalysts. ESR analysis shows that Cu-TCPP(BA)-MOF/PMS/vis system produces a large amount of non-radical 1O2. Also under visible light, with E. coli concentration of 107cfu/mL, it can be completely inactivated within 50 min. Dilution spreading plate method and Fluorescence spectroscopy confirmed the complete death of bacteria. In terms of mechanism, the ultra-thin MOF provides a large number of Cu2+ active sites. Under visible light, the cycle between Cu2+ and Cu+ is accelerated and the pathways that produce reactive oxygen species (ROS) is changed, thereby improving the performance of contaminant treatment and sterilization.

Photocatalytic Advanced Oxidation Processes for Neutralizing Free Cyanide in Gold Processing Effluents in Arequipa, Southern Peru

Cyanide (CN−) from gold processing effluents must be removed to protect human health and the environment. Reducing the use of chemical reagents is desirable for small centralized and decentralized facilities. In this work, we aimed to optimize the use of ultraviolet (UV) radiation coupled with hydrogen peroxide (H2O2) to enhance the rate and extent of CN− removal in synthetic and actual gold processing effluents, from one centralized and one decentralized facility in southern Peru. Bench-scale studies conducted using H2O2 and ambient UV showed no significant effects on CN− destruction; however, experiments with higher UV intensity and H2O2 accelerated free CN− degradation. When a 1:1 stoichiometric ratio of CN−:H2O2 was tested, the highly concentrated effluent (1 g CN−/L) had a slower pseudo first-order rate constant (k = 0.0066 min−1) and took ~5 h longer to reach 99% destruction, compared with the low concentration effluent (100 mg CN−/L; k = 0.0306 min−1). Lastly, a TiO2 photocatalyst with low stoichiometric CN−:H2O2 ratios (1:0.1 and 1:0.2), in a compound parabolic solar concentrator, was tested to investigate the degradation of a high concentration effluent (1.28 g CN−/L). These results show a significant improvement to degradation rate within a 20 min period, advancing treatment options for mineral processing facilities.

Comparative photocatalytic dye and drug degradation study using efficient visible light-induced silver phosphate nanoparticles.

The industrialization, growing population, and human activities (e.g., liquid waste of households, industrial units, and agricultural lands) are the main causes to contaminate fresh water sources. To overcome this issue, many techniques have been applied for water purification and chemical oxidation is one of the effective ways to treat the wastewater called as advanced oxidation process (AOPs). In the present study, synthesized silver phosphate nanoparticles were employed as catalysts in the photocatalytic advanced oxidation process for the degradation of various dyes (RhB, MB, MO, and OG) and drug (SMZ). The photocatalyst was characterized through different analytical tools, e.g., PXRD, FTIR, UV-Vis DRS, DLS, FESEM, and HRTEM. The chemical behavior or interaction of dye molecule with catalyst surface has also been explored to understand the mechanism of photodegradation reaction. All the organic dyes and drugs showed pseudo first-order rate kinetics and it was found that RhB dye and SMZ drug degraded so fast by the photocatalyst. The maximum observed photodegradation rate was 0.0744 min-1 for SMZ drug and 0.0532 min-1 for RhB dye, respectively. The minimum dye degradation was observed ~ 0.0036 min-1 for OG, which is ~ 15 times lesser than the degradation rate of RhB dye. From the comparative dye degradation study, it was found that the photodegradation efficiency of organic pollutants depends on the surface charge of the photocatalyst. The role of photogenerated reactive species (holes, superoxides, and hydroxyl free radicals) was also studied using different types of scavengers which helped to understand the photochemical reactions and mechanism by photocatalyst. The real sample analysis of textile effluent was also performed using the best photocatalyst in the presence of light.

Photocatalytic Advanced Oxidation Processes for Water Treatment: Recent Advances and Perspective.

Nowadays, an ever-increasing variety of organic contaminants in water has caused hazards to the ecological environment and human health. Many of them are persistent and non-biodegradable. Various techniques have been studied for sewage treatment, including biological, physical and chemical methods. Photocatalytic advanced oxidation processes (AOPs) have received increasing attention due to their fast reaction rates and strong oxidation capability, low cost compared with the non-photolytic AOPs. This review is dedicated to summarizing up-to-date research progress in photocatalytic AOPs, such as Fenton or Fenton-like reaction, ozonation and sulfate radical-based advanced oxidation processes. Mechanisms and activation processes are discussed. Then, the paper summarizes photocatalytic materials and modification strategies, including defect chemistry, morphology control, heterostructure design, noble metal deposition. The future perspectives and challenges are also discussed.

Feasibility study of UV assisted different heterogenous photo-catalytic methods for degradation of 2-nitrophenol in aqueous phase

In the present investigation, degradation of 2-nitrophenol (2-NP) in water was studied in laboratory-scale photo-reactor using different photocatalytic advanced oxidation processes (viz·H2O2/UV, Fe2+/H2O2/UV, Fe3+/H2O2/UV and TiO2/H2O2/UV). Parametric studies on these systems were carried out to determine the most favorable pH and stoichiometric oxidant/substrate ratio. This study revealed that the Fe3+/H2O2/UV photo-Fenton process is more competent and 100% COD could be removed within 75 min. of the reaction time. The substrate and oxidant (H2O2) concentration decay profiles signifies first order reaction.

Synergistic effect of TiO2 photocatalytic advanced oxidation processes in the treatment of refinery effluents

Different types of photolytic and photocatalytic advanced oxidation processes (AOPs) were used for treatment of refinery effluents from bitumen production. The treatment efficiency was evaluated by analyzing chemical oxygen demand (COD), biological oxygen demand (BOD5), volatile organic compounds (VOCs) and sulfide ions concentration. The studies revealed a synergistic effect of application of external oxidants (O3, H2O2, O3/H2O2) with TiO2 and UV applied for improved COD and BOD5 reduction as well as the degradation of the VOCs present in the effluents. Among studied processes a photocatalytic process combined with peroxone (TiO2/UV/O3/H2O2) was the optimal and the most economical technology. It allows to reduce 38 and 32% of COD and BOD5 respectively and degrade 84% of total VOCs in 280 min of treatment. At this conditions the reduced COD exceeds over 30% a theoretical value based on the dose of oxidants, which proves the importance of photocatalysis in the developed technology. The sulfide ions were completely depleted in all experiments in the first 30 min of treatment. The addition of TiO2 in the AOPs technology revealed a decrease in the process cost using less amount of chemicals achieving similar treatment efficiency when comparing with photolytic and non-catalytic technologies. The application of these technologies can be conducted in two alternative scenarios; whether to deplete the sulfides ions concentration or to maximize the treatment efficiency. In both options, the technologies studied are promising as a pre-treatment before other types of AOPs effective at neutral/acidic pH values or before a biological treatment stage. Further studies should be developed, by scaling up the process to a pilot scale in a real case scenario to check the possibility of its implementation in the industrial practice.

Lanthanum orthovanadate/bismuth oxybromide heterojunction for enhanced photocatalytic air purification and mechanism exploration

In this work, Lanthanum orthovanadate (LaVO4)/bismuth oxybromide (BiOBr) hybridized heterojunction was fabricated through a facile hydrothermal method for enhancing separation and transferring efficiency of photogenerated charge carriers in photocatalytic advanced oxidation process. The photoelectrochemical data demonstrate that the introduction of LaVO4 not only improves the solar energy harvesting efficiency due to decreasing of bandgap energies from 2.71 eV to 2.17 eV, but also reduces the transfer resistance of charge carriers in the hybridized system. Furthermore, the LaVO4/BiOBr heterojunctions exhibit enhanced photocatalytic degradation for gaseous air pollutants under visible light irradiation in comparison with bare LaVO4 and BiOBr. Among them, 3% LaVO4/BiOBr displays the best photocatalytic performance and degradation conversions of acetone and toluene achieve to 95.4% for 3 h and 87.1% for 4 h, respectively, which are 2.6 and 5.3 times higher than that of pristine BiOBr sample, respectively. Moreover, the OH and O2− were identified as the main radicals during the photo-degradation process. Based on the results of in-situ infrared spectra, a series of intermediates at different oxidation stages, including alcohols, aldehydes, and acids are captured, strongly supporting the proposed photoactive mechanism at gas/solid interface, which is beneficial for understanding the whole reaction process and pursuing new path to eliminating indoor air pollution.

Application of ZnO-Ag-Nd nanocomposite as a new synthesized nanophotocatalyst for the degradation of organic compounds: kinetic, thermodynamic and economic study.

In the present research, a zinc oxide (ZnO)-silver (Ag)-neodymium (Nd) nanocomposite was synthesized via the combustion method for the degradation of dyes as organic pollutants. The synthesized nanophotocatalyst was characterized using X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy techniques. The process of organic pollutant (Acid Red 18) removal was carried out in a semi-batch photoreactor equipped with an ultraviolet lamp. Also, the influence of key operational parameters such as pH, temperature, initial concentration of solution, and nanophotocatalyst dosage was investigated to evaluate kinetic and thermodynamic properties. Under optimum process conditions (pH = 6.21, dosage of nanophotocatalyst = 0.08 g/l, and low initial concentration of the solution), degradation of pollutant was monitored by measuring the total organic carbon of the solution. Finally, an economic study showed that the photocatalytic advanced oxidation process is an viable treatment method for low concentrations of organic pollutants.

Catalytic and Photocatalytic Processes for the Abatement of N-Containing Pollutants from Wastewater. Part 2: Organic Pollutants

Several N-containing organic compounds of anthropic origin, namely dyes, pesticides/herbicides and pharmaceuticals, are responsible of water pollution, due to their high solubility in water and low adsorption in soil, leading to a high mobility in the aquifer. Besides pesticides and dyes, widely recognized as water pollutants, environmental contamination by pharmaceuticals is an emerging issue, since both drugs and their metabolites may act as water pollutants, and most of water potabilization plants do not treat them. Removal of such species by physico-chemical methods (adsorption and coagulation; sedimentation; filtration; use of membranes and chlorination) suffers from several drawbacks, including high operating costs, and formation of secondary pollutants that are then released in the environment. Nonetheless, currently employed biological methods do not allow removing nonbiodegradable pollutants. Advanced oxidation processes (AOPs), which imply the in situ production of highly reactive species (i.e., H2O2, OH, O− 2 , O3 under relatively mild experimental conditions, allow the degradation (and eventual mineralization to CO2 and H2O) of refractory organics into readily biodegradable compounds and may be used either before or after biological treatments. This review addresses the most common catalytic and photocatalytic AOPs that can be adopted for the removal of some N-containing compounds of different origin and nature.

Comparative analysis of UV-C/H2O2 and UV-A/TiO2 processes for the degradation of diclofenac in water

The study investigates the treatment of diclofenac (DCF), a pharmaceutical included in the first watch list of the European Water Framework Directive as a new potential priority substance in water. Since the conventional wastewater treatment technologies do not efficiently remove DCF, advanced treatment technologies capable of its complete removal or destruction of its biological activity, need to be evaluated and eventually employed. For that purpose, typical representatives of photooxidative and photocatalytic advanced oxidation processes were applied. The effectiveness of UV-C/H2O2 and UV-A/TiO2 were compared regarding DCF conversion and mineralization kinetics, water quality parameters for assessing biodegradability and toxicity. In spite of similar biodegradability profiles, the obtained results indicate different DCF degradation pathways, which are reflected in different profiles of toxicity towards Vibrio fischeri. The observed DCF conversion and mineralization kinetics revealed the benefits of UV-C/H2O2 process. However, lower toxicity favored the application of photocatalytic over photooxidative treatment for DCF removal.