Photocatalytic Ozonation Process Research Articles

The role of TiO2 and gC3N4 bimetallic catalysts in boosting antibiotic resistance gene removal through photocatalyst assisted peroxone process

Antibiotics are extensively used in human medicine, aquaculture, and animal husbandry, leading to the release of antimicrobial resistance into the environment. This contributes to the rapid spread of antibiotic-resistant genes (ARGs), posing a significant threat to human health and aquatic ecosystems. Conventional wastewater treatment methods often fail to eliminate ARGs, prompting the adoption of advanced oxidation processes (AOPs) to address this growing risk. The study investigates the efficacy of visible light-driven photocatalytic systems utilizing two catalyst types (TiO2-Pd/Cu and g-C3N4-Pd/Cu), with a particular emphasis on their effectiveness in eliminating blaTEM, ermB, qnrS, tetM. intl1, 16 S rDNA and 23 S rDNA through photocatalytic ozonation and peroxone processes. Incorporating O3 into photocatalytic processes significantly enhances target removal efficiency, with the photocatalyst-assisted peroxone process emerging as the most effective AOP. The reemergence of targeted contaminants following treatment highlights the pivotal importance of AOPs and the meticulous selection of catalysts in ensuring sustained treatment efficacy. Furthermore, Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) analysis reveals challenges in eradicating GC-rich bacteria with TiO2 and g-C3N4 processes, while slight differences in Cu/Pd loadings suggest g-C3N4-based ozonation improved antibacterial effectiveness. Terminal Restriction Fragment Length Polymorphism analysis highlights the efficacy of the photocatalyst-assisted peroxone process in treating diverse samples.

Removal of acid red dye 1 from textile wastewater by heterogenous photocatalytic ozonation employing titanium dioxide and iron zeolite

Clean water is a necessity for all life to survive and flourish. However, natural waters are being continuously contaminated due to the release of waste streams in water. Hence, it is important to remove pollutants from wastewater to fulfill human needs. Conventional treatment methods are neither efficient nor economical for wastewaters that especially contain refractory toxic pollutants. This requires novel techniques like Advanced oxidation processes (AOPs), that may successfully degrade persistent micropollutants more efficiently. In this study, an azo dye Acid Red 1 was removed by three AOPs, namely Photocatalytic oxidation, Ozonation and Photocatalytic Ozonation, by employing heterogenous catalysts. TiO2 was used as photocatalyst, whereas Fe-Zeolite has been further added as Ozonation catalyst. The study revealed that photocatalysis degraded only 28% Acid red dye after 15 min, whereas for ozonation, the degradation percentage was 95% in same time. In combined photocatalytic ozonation process using TiO2, 95% degradation was achieved in just 9 min and treatment time further reduced to 5 min when Fe-zeolite was added. Optimization studies for initial concentration, UV intensity and catalyst loading were performed. Finally, rate constants and Electrical Energy per Order (EEO) values were determined for all AOPs, and mechanism was proposed.

Treatability of BPA Containing Wastewater by Catalytic and Photocatalytic Ozone Processes Using n.TiO2

In this study, the treatment of synthetic wastewater containing 10 mg/L Bisphenol A (BPA) has been investigated by the catalytic and photocatalytic ozonation process. n.TiO2 nanocatalysts have been used in catalytic (COP) and photocatalytic (PCOP) ozonation processes. Optimum parameters have been determined as pH 6.32, 1200 mg/L ozone dose, 50 mg/L n.TiO2 catalyst dose and 12.5 min reaction time for COP. Optimum parameters have been found as pH 6.32, 1200 mg/L ozone dose, 50 mg/L n.TiO2 catalyst dose, 18 Watt UV light intensity, and 10 min reaction time for PCOP. The removal efficiencies of BPA have been obtained as 95.51% and 98.09% for COP and PCOP, respectively. Kinetic analyses showed that BPA removal has been carried out Pseudo second order kinetics with R2 values of 99.1 for both processes.

On the geometry and material stability of tubular PVDF-TiO2 static mixer membrane contactors for photocatalytic ozonation of micropollutants

The prevention of ozone hotspots in ozonation reactors for wastewater treatment is essential for effective degradation of micropollutants without forming harmful by-products. Membrane contactors can provide a bubble-free ozonation process that is able to decrease by-product formation, e.g., bromate formation in bromide-charged wastewater. Furthermore, the geometry of the reactor influences the distribution of dissolved ozone in a membrane contactor. Turbulence promoters can significantly decrease ozone hotspots and increase ozone mass transfer into wastewater. This work presents a fabrication methodology to produce PVDF-TiO2 helical static mixer membranes using the rotation-in-a-spinneret technology. Static mixer membranes combine the functionality of a membrane contactor and a static mixer in a single component. Furthermore, the PVDF matrix is doped with TiO2 particles as photocatalyst. Thus, we present a membrane-based photocatalytic ozonation process to increase the concentration of hydroxyl radicals for degradation of micropollutants under UV radiation. Static mixer membranes increase the ozone mass transfer coefficient by 70% compared to conventional hollow fiber membranes. Furthermore, the specific photocatalytic degradation rate of methylene blue increases by 50% using static mixer membranes. However, this work also reveals a lack of long-term stability of PVDF-TiO2 membranes in the corrosive environment of photocatalytic ozonation. The molecular weight of PVDF decreases by 11% after use in photocatalytic ozonation resulting in a loss of mechanical stability of the membranes. Similar material concepts are required based on ceramic materials which avoid wetting of the porosity.

Emerging contaminants and pathogenic microorganisms elimination in secondary effluent by graphitic carbon nitride photocatalytic ozonation processes

The complexity of water contaminants, both chemical and biological requires an efficient and feasible treatment alternative. Herein, the photocatalytic ozonation treatment using graphitic carbon nitride catalysts was effectively applied for the elimination of a mixture of targeted chemical contaminants, and both Escherichia coli bacteria and Human polyomavirus JC (JC virus) in real secondary wastewater. The exfoliation treatment was compared in catalysts prepared using urea and melamine as precursors. The physical treatment provided no significant enhancement in the urea-based catalyst, while the improvement in the structure of the melamine-based (36MCN) material and formation of melem heterojunction increased its catalytic properties. In both sets of contaminants, the photocatalytic ozonation systems were superior to photolytic ozonation, especially regarding ozone consumption. The best catalyst, 36MCN, resulted in a decrease of 57.5%, 33.0% and 29.0% in the ozone dose required to eliminate chemical, bacteria and virus contaminants, respectively. The hydroxyl radicals were also shown as a key responsible for the pollutant’s elimination. The higher radical production and decomposition of ozone are possible indications of the better performance of graphitic carbon nitride photocatalytic ozonation, as an efficient tertiary wastewater alternative.

Comparative study of visible-light active BiOI and N,Pd-TiO2 photocatalysts: Catalytic ozonation for dye degradation

The increasing demand for clean water requires the development of simple, cheap, and efficient catalysts systems for water pollution remediation. To develop cheap yet efficient hybrid advanced oxidation processes for degradation of organic pollutants in water requires their systematic comparison under similar conditions to make informed decisions of economically feasible and sustainable systems. Visible light active single BiOI and N, Pd co-doped TiO2 were investigated for photocatalytic ozonation (PCO) for methylene blue (MB) degradation. Metal and non-metal co-doping improved morphology, band structure and active sites on the surface of TiO2 to shift its light absorption into the visible region. The degradation of MB with BiOI PCO and N,Pd-TiO2 PCO was practically similar but showed improvement of the ozonation mineralization efficiency. However, mineralization of MB on BiOI PCO surpassed that of N,Pd-TiO2 PCO due to band structure that influenced generated free radicals during the PCO processes. BiOI PCO system progressed through the existence and involvement of strongly oxidizing and non-selective hydroxyl radicals towards enhanced mineralization of dye and intermediates while N,Pd-TiO2 PCO was steered by the superoxide radical that is selective and had lower mineralization efficiency of formed intermediates despite its high initial degradation efficacy. The work demonstrated cheap and efficient visible light active semiconductors like BiOI as potential candidates for application in photocatalytic ozonation for real applications with matching activities to that of co-doped UV active semiconductors like TiO2. This work advances the use of visible light active semiconductors towards PCO based processes for environmental pollution remediation.

Tocilizumab degradation via photo-catalytic ozonation process from aqueous

Following the advent of the coronavirus pandemic, tocilizumab has emerged as a potentially efficacious therapeutic intervention. The utilization of O3-Heterogeneous photocatalytic process (O3-HPCP) as a hybrid advanced oxidation technique has been employed for the degradation of pollutants. The present study employed a solvothermal technique for the synthesis of the BiOI-MOF composite. The utilization of FTIR, FESEM, EDAX, XRD, UV–vis, BET, TEM, and XPS analysis was employed to confirm the exceptional quality of the catalyst. the study employed an experimental design, subsequently followed by the analysis of collected data in order to forecast the most favorable conditions. The purpose of this study was to investigate the impact of several factors, including reaction time (30–60 min), catalyst dose (0.25–0.5 mg/L), pH levels (4–8), ozone concentration (20–40 mMol/L), and tocilizumab concentration (10–20 mg/L), on the performance of O3-HPCP. The best model was discovered by evaluating the F-value and P-value coefficients, which were found to be 0.0001 and 347.93, respectively. In the given experimental conditions, which include a catalyst dose of 0.46 mg/L, a reaction time of 59 min, a pH of 7.0, and an ozone concentration of 32 mMol/L, the removal efficiencies were found to be 92% for tocilizumab, 79.8% for COD, and 59% for TOC. The obtained R2 value of 0.98 suggests a strong correlation between the observed data and the predicted values, indicating that the reaction rate followed first-order kinetics. The coefficient of synergy for the degradation of tocilizumab was shown to be 1.22. The catalyst exhibited satisfactory outcomes, but with a marginal reduction in efficacy of approximately 3%. The sulfate ion (SO42−) exhibited no influence on process efficiency, whereas the nitrate ion (NO3−) exerted the most significant impact among the anions. The progress of the process was impeded by organic scavengers, with methanol exhibiting the most pronounced influence and sodium azide exerting the least significant impact. The efficacy of pure BiOI and NH2-MIL125 (Ti) was diminished when employed in their pure form state. The energy consumption per unit of degradation, denoted as EEO, was determined to be 161.8 KWh/m3-order.

C vacancy and F decorated g-C3N4 for boosting photocatalytic ozonation of sodium p-perfluorinated nonoxybenzenesulfonate

Photocatalytic ozonation (PCO) was a novel water treatment method, but the low photo-generated electron (e-) utilization and ambiguous ROS formation mechanism restrained its performance. Herein, C vacancy and F co-decorated g-C3N4 (FCN_Cv) was designed to accelerate the PCO performance with sodium p-perfluorinated nonoxybenzenesulfonate (OBS) acting as model pollutant. Comparative characterizations revealed that FCN_Cv remained the inherent structure of g-C3N4 (BCN), and had an enhanced conduction band potential, narrower band gap and longer e- lifetime. FCN_Cv exhibited the greater activity over BCN, with 99.3 % OBS removal in 30 min but only 78.3 % for BCN during PCO process. •OH was the main ROS for degrading OBS. The greater •OH yield was obtained by FCN_Cv PCO process because of the increase of e- utilization. On one hand, the two electrons reduction of O2 into H2O2 on FCN_Cv was accelerated, which triggered the peroxone reaction between photogenerated-H2O2 and O3. On the other hand, the direct one electron reduction of O3 by e- also accounted for •OH generation. 17 kinds of intermediates were detected and the OBS degradation routes were inferred, which was involved with hydroxylation, C-O cleavage and aromatic ring opening reactions. Overall, this study demonstrated the feasibility of decorating F element and C vacancy on g-C3N4 in enhancing e- utilization and •OH generation during PCO process as well as deepened the understanding of fate of OBS in PCO process.

Light-assisted catalytic ozonation for efficient degradation of ciprofloxacin using NiO/MoS2 nanocomposite

In this study, the hydrothermal method was used to prepare NiO/MoS2 nanocomposite which was employed for the first time in the photocatalytic ozonation (PCO) process to degrade ciprofloxacin antibiotic. The synthesized nanocatalyst was analyzed with various characterization techniques. Response surface methodology (RSM) was utilized to conduct the statistical analysis and optimization of the influential parameters in the degradation process. The maximum efficiency for ciprofloxacin removal (100%) was attained at pH = 5.8, by employing 0.37 g L-1 of the NiO/MoS2 nanocatalyst, an ozone (O3) flow rate of 0.2 g L-1h−1 and duration of 12 min. The results indicated a significant synergistic effect in the analyzed system, which supports the proposal that utilizing the photocatalyst and ozone together through the PCO process is a more efficient method. Also, according to the kinetic analysis data, the PCO process conformed to obey the pseudo-first-order model. Furthermore, the nanocatalyst exhibited a high level of recyclability and stability, retaining 85.44% efficiency after undergoing five successive photocatalytic ozonation cycles. In conclusion, the obtained results confirm that the O3/Vis/NiO/MoS2 system is a promising approach for the treatment of wastewaters containing emerging pharmaceutical contaminants.

Efficient treatment of surfactant containing wastewater by photocatalytic ozonation with BiPO4 nanorods

In this study, monoclinic BiPO4 nanorods were fabricated by one-pot solvothermal method. Its catalytic capability in photocatalytic ozonation process was tested by degradation and mineralization of sodium dodecyl benzene sulfonate (SDBS) solution. The results demonstrated that the TOC removal rate was dramatically improved to 90.0% at 75 min for UV/O3/BiPO4 process, which was 4.9 and 3.8 times more than that of UV/BiPO4 and O3. Moreover, the pseudo-first-order kinetic constant (0.337 min−1) and mineralization rate (90.0%) for SDBS degradation using BiPO4 in UV/O3 process were 1.6 and 1.3 times as great as that of conventional TiO2 photocatalyst (0.206 min−1, 67.3%). The influence of BiPO4 dosage, O3 concentration initial pH and coexisted ions on SDBS degradation in UV/O3/BiPO4 process were also investigated. The outcome of quenching studies illustrated both ·OH and h+ contributed prominently to SDBS degradation in UV/O3/BiPO4 process, implying that high valence band position of BiPO4 could promote the synergism between photocatalysis and ozonation. The degradation pathway of SBDS was proposed by combination of intermediates analysis and DFT calculation. Real carwash wastewater was chosen as typical surfactant containing wastewater to explore the practical application of UV/O3/BiPO4 technology. During 30 min, COD and LAS removal efficiency reached 59.7% and 70.6%, respectively. The quality indices of effluent could meet the requirements for reuse of carwash water in Water Quality Standard for Urban Miscellaneous Use in China. Energy consumption in the process was calculated as 13.9 kW h m−3, which was about 3.6 and 2.2 times less than that of UV/BiPO4 and O3 process, respectively. The results suggest that UV/O3/BiPO4 system has an application potential for surfactant containing wastewater treatment or recycle.

Advance oxidation processes of Rhodamine B under O3/UV using spent bleaching earth-ZnO composite: Performance in kinetics

Spent bleaching earth and ZnO composite (SBE/ZnO) was prepared as the catalyst for the advanced oxidation processes (AOPs) of rhodamine B (RB) under O3/UV. The photocatalytic ozonation process of RB was conducted at an ozone flow rate of 1 L/min by adjusting the variation of initial RB concentration, catalyst dosage, and reaction time. The RB removal efficiency of 96.7% was reached within 36 min at optimal operational conditions (initial concentration of 100 mg/L and catalyst dosage of 1.5 g). The kinetical analysis at this condition showed that the photocatalytic ozonation process of RB followed a pseudo-first-order reaction with a rate constant of 0.0975 min-1. Meanwhile, the effect of operational variables was evaluated using response surface methodology (RSM) and resulted in an optimized model for RB Removal following equation: RB Removal = 84.95 - 6.24A + 5.81B + 22.45C + 3.07AB + 13.14AC - 6.72BC + 0.1174A2 + 7.86B2 - 8.90C2, where A is the initial concentration of RB, B is catalyst dose and C is reaction time, with a high coefficient of determination R2 = 0.9432.

Solar-based photocatalytic ozonation employing novel S-scheme ZnO/Cu2O/CuO/carbon xerogel photocatalyst: effect of pH, salinity, turbidity, and temperature on salicylic acid degradation.

This paper proposes the study of a solar-based photocatalytic ozonation process for the degradation of salicylic acid (SA) using a novel S-scheme ZnO/Cu2O/CuO/carbon xerogel photocatalyst. The incorporation of CuO and Cu2O aims to enhance charge mobility through the formation of p-n heterojunctions with ZnO, whereas the carbon xerogel (XC) was selected due to its eco-friendly nature, capacity to stabilize S-scheme heterojunctions as a solid-state electron mediator, and ability to function as a reducing agent under high temperatures. The characterization of the composites demonstrates that the presence of the XC during the calcination step led to the reduction of a fraction of the CuO into Cu2O, forming a ternary semiconductor heterojunction system. In terms of photocatalysis, the XC/ZnO-CuxO 5% composite achieved the best efficiency for salicylic acid degradation, mainly due to the stabilization of the S-scheme charge transfer pathway between the ZnO/CuO/Cu2O semiconductors by the XC. The total organic carbon (TOC) removal during heterogeneous photocatalysis was 80% for the solar-based process and 68% for the visible light process, after 300 min. The solar-based photocatalytic ozonation process was highly successful regarding the degradation of SA, achieving a 75% increase in the apparent reaction rate constant when compared to heterogeneous photocatalysis. Furthermore, a 78% TOC removal was achieved after 150 min, which is half the time required by the heterogeneous photocatalysis to obtain the same result. Temperature, salinity, and turbidity had major effects on the efficiency of the photocatalytic ozonation process; the system's pH did not cause any major performance variation, which holds relevance for industrial applications.

Enhancing Ibuprofen and 4-Isobutylacetophenone degradation: Exploiting the potential of Nb2O5 sol-gel catalysts in photocatalysis, catalytic ozonation, and photocatalytic ozonation

This study describes the synthesis of Nb2O5 by three sol-gel methods to be used as a catalyst in photocatalysis, catalytic ozonation and the synergistic effects of the two processes, photocatalytic ozonation in bath reactions for the degradation of ibuprofen and its degradation products, 4- Isobutylacetophenone and oxalic acid. The catalysts were prepared in three temperature ranges: non-calcined, calcined at 873 K and 1173 K, and were characterized using different techniques. The results demonstrate that the catalyst synthesized through Sol-gel Method 3 and heat-treated at 873 K achieved the highest pollutant removal in photocatalytic tests (92% with 95% TOC reduction) over 300 min of reaction, and in the catalytic ozonation tests (100% with 62% TOC reduction) over 30 min of reaction, due to the combination of the properties presented in the characterization analyzes. Thus, this catalyst was employed in photocatalytic ozonation reactions and demonstrated the capability to degrade 100% of ibuprofen in 12 min without 4-IBAP formation, resulting in a 98% reduction in TOC over 30 min of reaction. In addition, the photostability outcomes of this catalyst demonstrated no significant reduction in catalytic activity during the photocatalytic and catalytic ozonation processes and comparable results to P25. The toxicity tests validated the TOC results, showing an 8% effect vs. 90% of ibuprofen starting solution, and 43% effect vs. 95% of 4-IBAP starting solution.

Photocatalytic-ozonation process in oxytetracycline degradation in aqueous solution: composite characterization, optimization, energy consumption, and by-products

In this research, we synthesized BiOI/NH2-MIL125(Ti) via solvo-thermal method to investigation of oxytetracycline (OTC) degradation in photocatalytic-ozonation process. The results of the XRD, FESEM, EDAX, FTIR, UV–Vis, TEM, XPS, and BET analyzes indicated that the catalyst BiOI/MOF was synthesized with excellent quality. Design of experiment (DOE), ANOVA statistical analysis, interaction of parameters and predicated optimum condition was done based on CCD. The effect of catalyst dose (0.25–0.5 mg/l), pH (4–8), reaction time (30–60 min) and O3 concentration (20–40 mN) at 10 mg/l of OTC on PCO/O3 process was optimized. Based on P-value and F-value coefficients (0.0001, 450.3 respectively) the model of OTC (F-value = 2451.04) and (P-value = 0.0001) coefficients, the model of COD removal was quadratic model. Under optimum condition pH 8.0, CD = 0.34 mg/l, RT = 56 min and O3 concentration = 28.7 mN, 96.2 and 77.2% of OTC and COD removed, respectively. The reduction of TOC was 64.2% in optimal conditions, which is less than the reduction of COD and OTC. The kinetics of reaction followed pseudo-first-order kinetic (R2 = 0.99). Synergistic effect coefficient was 1.31 that indicated ozonation, presence of catalyst and photolysis had a synergistic effect on OTC removal. The stability and reusability of the catalyst in six consecutive operating steps was acceptable and 7% efficiency decreased only. Cations (Mg2+, and Ca2+), SO42− had no influence on performing the process, but other anions, organic scavengers, and nitrogen gas, had an inhibitory effect. Finally, the OTC degradation probably pathway includes direct and indirect oxidation that decarboxylation, hydroxylation, demethylation and were the main mechanism in OTC degradation.

Uncommonly efficient degradation performance of photocatalytic ozonation towards tetracycline over synthesizing 3-D g-C3N4 nanosheet based on Si-O-Co framework

3D g-C3N4/Co-MCM-48 was successfully prepared by constructing mesoporous Si-O-Co framework as the template for loading g-C3N4 nanosheet. Excellent synergistic effect and stability in photocatalytic ozonation of tetracycline (TET) were observed owe to the ordered and unique catalyst structure. The results indicated that g-C3N4/Co-MCM-48 possessed better catalytic performance for TET degradation and had an apparent advantage compared with bulk g-C3N4. The highly dispersed Co atoms in the framework acted as reaction centers of ozonation and promoted separation of photo-induced carriers, which further improved the synergistic effect and produced abundant reactive oxygen species (ROSs). Meanwhile, the increase of specific surface area provided sufficient active sites for catalysis. The degradation rate of TET by simulated solar light/g-C3N4/Co-MCM-48/O3 was close to 100% within 8 min, and both the kinetic constant and synergy index of TET degradation were 7.8 and 4.9 times as much as that of simulated solar light/g-C3N4/O3. Effects of various initial pH and Co contents on the TET degradation were studied. In addition, g-C3N4/Co-MCM-48 revealed good stability in photocatalytic ozonation process by cycling for four times, and the pathway of TET degradation was also proposed in this study. It was suggested that g-C3N4/Co-MCM-48 was an excellent catalyst for the practical application of photocatalytic ozonation.

Application of plant-based coagulant with a novel MnO2.MoS2 nanocatalyst in coagulation/photocatalytic ozonation process for wastewater treatment

ABSTRACT In this work, Lallemantia royleana seed mucilage (LRSM) was applied as a plant based coagulant in the initial stage of an integrated method for dye degradation. Photocatalytic ozonation (PCO) process was used under visible-light irradiation in the post-treatment stage. MnO2.MoS2 heterostructure nanocomposite was fabricated by hydrothermal synthesis and applied for the first time in PCO to mineralize Acid Blue 113 dye. The synthesized nanocatalyst was characterized by FT-IR, XRD, FE-SEM, TEM, DRS and BET. Characterization of the nanocatalyst showed that the composite consisted MoS2 with a sheet-like structure and MnO2 in the form of nanoparticles with different sizes in the range of 15–30 nm. By using the response surface methodology (RSM) approach, the best operational condition in the coagulation-flocculation (CF) stage has been acquired at pH 5.0, LRSM dose of 220 mg/L within 27 min. By applying the PCO process, complete decolorization has been attained using 11 mg of the catalyst and 0.2 g/L.h ozone dosage within 9 min. The use of LRSM along with MnO2.MoS2 nanocatalyst in the CF/PCO combined process for treating real wastewater samples indicates that the proposed technique is highly efficient and can be effectively employed to treat dye-containing industrial effluents.

Synergistic effect of exposed facets and surface defects of ZnO nanomaterials for photocatalytic ozonation of organic pollutants

The exposed facets and surface defects of ZnO significantly influenced the production of reactive oxidation species in the photocatalytic ozonation process.

Efficient Dye Removal Using Fe3O4.MnO2.MoS2 Nanocomposite in Optimized Photocatalytic Ozonation Process

ABSTRACT In this study, Fe3O4.MnO2.MoS2 nanocatalyst has been fabricated for the first time and applied in the photocatalytic ozonation (PCO) process. The efficiency of this ternary heterostructure nanocomposite was evaluated in the removal of Acid Blue 113 (AB113) dye with 100 mg.L−1 concentration utilizing response surface methodology (RSM). The optimal condition of the process was attained at pH = 3, using 2 mg of the nanocatalyst and 300 mg.L−1 ozone dosage applied over 20 min. High efficiency of AB113 removal (99%) was observed at the optimal condition. In addition, the performance of the synthesized catalyst in the PCO process was investigated in the treatment of a real textile effluent sample. The PCO has been found to be more efficient than the individual photocatalysis and catalytic ozonation methods due to the synergistic effect between the two oxidation systems. The results proved that Fe3O4.MnO2.MoS2 can be used as a highly efficient catalyst in the PCO process.

Carbon nitride photoactivation evaluation and degradation of a mixture of parabens by ozone assistance

Graphitic carbon nitride was investigated as an efficient and cheap catalyst for the degradation of a mixture of parabens through photo-aided processes. The ozone and g-C3N4 system was explored to obtain lacking necessary information regarding this combination for the proposed contaminants. The influence of key parameters was investigated to better understand the behavior of system and optimize it. Ultraviolet-A radiation promoted a more efficient activation of g-C3N4 compared to visible light. The photocatalytic ozonation process achieved higher parabens degradation rates and lower ozone consumption than the single technologies, reducing its overall cost. Basic and neutral conditions (pH = 7–11) promoted a better interaction between catalysts and contaminants, and radicals' formation. A catalyst concentration of 500 mg L−1 and parabens concentration of 1 mg L−1 resulted in >95 % removal of the three parabens within 15 min and with a lower transferred ozone dose required. Toxicity towards Allivibrio fischeri bacteria demonstrated a significant decrease in its luminescence inhibition after photocatalytic ozonation treatment, resulting in a non-toxic solution.

Degradation of cefadroxil by photoelectrocatalytic ozonation under visible-light irradiation and single processes

Here, we investigate the degradation of 20 mg L-1 Cefadroxil (CFX) in water using photoelectrocatalytic ozonation (PECO), and compared against its individual processes. A carbon nitrogen-codoped titanium dioxide (CN-TiO2) anode is synthesized using ethylene glycol and ethylenediamine as carbon and nitrogen source, respectively. The X-ray diffraction (XRD) and Scanning Electronic Microscopy (SEM) analysis conducted to this material indicate a crystalline phase anatase with irregular morphology formed on the electrode surface; while the diffuse reflectance spectroscopy (DRS) shows a shift in the photoanode absorbance towards the visible region, unlike undoped TiO2 structure. This behavior results from the inclusion of Carbon and Nitrogen species on the CN-TiO2 electrode in weight percentages of 14.5 and 1.61 wt%, respectively, according to Energy Dispersive Spectroscopy (EDS) analysis. The Cefadroxil (CFX) abatement is monitored UV–Vis spectroscopy, high-performance liquid chromatography (HPLC), and total organic carbon (TOC). All techniques reveal that the highest CFX removal occurs with PECO (Photoelectrocatalytic Ozonation) process, decreasing TOC by 57.6% (96% degradation by HPLC) after 90 min of treatment. The main by-products formed from oxidation with the PECO, PCO (Photocatalytic Ozonation) and O3 (Ozonation) systems were acid species presumably corresponding to short chain carboxylic acids. Finally, the germination of lettuce sativa is carried out in water contaminated with the drug, and compared with water treated by PECO and PCO processes, showing that PECO process improves germination by 23.5% on the contaminated sample and 7.4% on the sample treated with PCO. These findings confirm that synergism of oxidation techniques could be a tractable way to resolve the problems related to recalcitrant compounds contained in wastewater.