High Decomposition Efficiency Research Articles

Controllable preparation of graphene glass fiber fabric towards mass production and its application in self-adaptive thermal management

Direct synthesis of graphene on nonmetallic substrates via chemical vapor deposition (CVD) has become a frontier research realm targeting transfer-free applications of CVD graphene. However, the stable mass production of graphene with a favorable growth rate and quality remains a grand challenge. Herein, graphene glass fiber fabric (GGFF) was successfully developed through the controllable growth of graphene on non-catalytic glass fiber fabric, employing a synergistic binary-precursor CVD strategy to alleviate the dilemma between growth rate and quality. The binary precursors consisted of acetylene and acetone, where acetylene with high decomposition efficiency fed rapid graphene growth while oxygen-containing acetone was adopted for improving the layer uniformity and quality. Notably, the bifurcating introducing-confluent premixing (BI-CP) system was self-built for the controllable introduction of gas and liquid precursors, enabling the stable production of GGFF. GGFF features solar absorption and infrared emission properties, based on which the self-adaptive dual-mode thermal management film was developed. This film can automatically switch between heating and cooling modes by spontaneously perceiving the temperature, achieving excellent thermal management performances with heating and cooling power of ∼501.2 and ∼108.6 W m−2, respectively. These findings unlock a new strategy for the large-scale batch production of graphene materials and inspire advanced possibilities for further applications.

Block-matching and 3D filtering algorithm in X-ray image with photon counting detector using the improved K-edge subtraction method

Among photon counting detector (PCD)-based technologies, the K-edge subtraction (KES) method has a very high material decomposition efficiency. Yet, since the increase in noise in the X-ray image to which the KES method is applied is inevitable, research on image quality improvement is essential. Here, we modeled a block-matching and 3D filtering (BM3D) algorithm and applied it to PCD-based X-ray images with the improved KES (IKES) method. For PCD modeling, Monte Carlo simulation was used, and a phantom composed of iodine substances with different concentrations was designed. The IKES method was modeled by adding a log term to KES, and the X-ray image used for subtraction was obtained by applying the 3.0 keV range based on the K-edge region of iodine. As a result, the IKES image using the BM3D algorithm showed the lowest normalized noise power spectrum value. In addition, we confirmed that the contrast-to-noise ratio and no-reference-based evaluation results when the BM3D algorithm was applied to the IKES image were improved by 29.36 % and 20.56 %, respectively, compared to the noisy image. In conclusion, we demonstrated that the IKES imaging technique using a PCD-based detector and the BM3D algorithm fusion technique were very efficient for X-ray imaging.

Unraveling the potential of sonochemically achieved DyMnO3/Dy2O3 nanocomposites as highly efficient visible-light-driven photocatalysts in decolorization of organic contamination

In the present day, the widespread presence of lingering contaminants in ecosystems has prompted scientists to develop novel semiconductor nanoarchitectures that assist in photocatalytic reactions mediated by visible light. As a result, we propose to prepare a series of Dy-Mn-O based nano-catalysts using a sonochemical approach utilizing various ionic phases of surfactants as structure-directing agents. In this study, X-ray diffraction (XRD) and Rietveld refinement techniques were used to explore the fundamental effects of surfactants on the compositional-structural features of the materials. In terms of morphological profiles, DyMnO3/Dy2O3 (DM) nanostructures fabricated with Triton X-80 as a structure-directing agent showed the best uniformity with an acceptable size range between 14.14 and 52.35 nm. In the visible-light-driven photocatalytic domain, these nanocomposites provide high responsiveness based on their optical band gap value of 2.0 eV. According to our findings, two individual factors affect dye activity, namely dye type and concentration, which is why a high decomposition efficiency of 78.8% was obtained for 10 ppm Acid violet (AV) using DyMnO3/Dy2O3 nanocomposites after 120 min of exposure to visible light. Furthermore, radical quenching test confirmation confirmed the mechanistic behind the degradation process. This indicates that active species of O2•− and •OH may play a significant role in photocatalysis. As a result of repeated processes over three consecutive cycles, binary DyMnO3/Dy2O3 nanocomposites had an efficiency of 64.4% in removing dyes from the environment, indicating their high stability.

Charactering Catalytic Ignition and Combustion for the Ninety-Percent Hydrogen-Peroxide/Paraffin-Based Hybrid Rocket Engine

The present work performed a combined experimental and numerical investigation of the catalytic ignition and combustion characteristics for a hybrid rocket engine (HRE) using 90% hydrogen peroxide () with a paraffin-based fuel as the propellant system. The variation of the decomposition temperature used as the analytical premise was monitored by a thermocouple and laser absorption spectroscopy based on water absorption. The effects of preheating, the number of silver mesh layers, and the usage count for the catalytic bed on the decomposition characteristics were analyzed. A preheated 60-layer silver catalyst bed provided the best decomposition performance, including the shortest catalytic decomposition delay time and the highest decomposition efficiency. A two-dimensional numerical model was built to determine the effect of decomposition efficiency decay on the HRE combustion characteristics. Variations in the combustion temperature, combustion chamber pressure, and product distribution were compared for decomposition efficiencies ranging from 70 to 100%. As the decomposition efficiency of decreased to 80%, part of the oxidizer was blown out the chamber before participating in the combustion, yielding a significant decline in the combustion performance of the hybrid rocket engine. Static firing tests were also used to determine the catalytic ignition and reignition performance of the HRE. The results showed that the performance of the catalytic bed was stable while the reignition process was rapid without a pressure peak.

Iron oxide/hydroxide–nitrogen doped graphene-like visible-light active photocatalytic layers for antibiotics removal from wastewater

Hybrid layers consisting of Fe oxide, Fe hydroxide, and nitrogen doped graphene-like platelets have been synthesized by an eco-friendly laser-based method for photocatalytic applications. The complex composite layers show high photodecomposition efficiency towards degradation of antibiotic molecules under visible light irradiation. The photodecomposition efficiency was investigated as a function of relative concentrations of base materials, Fe oxide nanoparticles and graphene oxide platelets used for the preparation of target dispersions submitted to laser irradiation. Although reference pure Fe oxide/Fe hydroxide layers have high absorption in the visible spectral region, their photodecomposition efficiency is negligible under the same irradiation conditions. The high photocatalytic decomposition efficiency of the nanohybrid layer, up to 80% of the initial antibiotic molecules was assigned to synergistic effects between the constituent materials, efficient separation of the electron–hole pairs generated by visible light irradiation on the surface of Fe oxide and Fe hydroxide nanoparticles, in the presence of conducting graphene-like platelets. Nitrogen doped graphene-like platelets contribute also to the generation of electron–hole pairs under visible light irradiation, as demonstrated by the photocatalytic activity of pure, reference nitrogen doped graphene-like layers. The results also showed that adsorption processes do not contribute significantly to the removal of antibiotic molecules from the test solutions. The decrease of the antibiotic concentration under visible light irradiation was assigned primarily to photocatalytic decomposition mechanisms.

Ag-decorated CuO NW@TiO2 heterojunction thin film for improved visible light photocatalysis

Herein, Ag-decorated CuO@TiO2 (CuO@TiO2-Ag) semiconductor heterojunctions are prepared using a porous CuO nanowire (NW) matrix for visible light photocatalysis applications. The CuO NW matrix is synthesized by wet-oxidation-based growth on a commercial Cu plate. Conformal coating of TiO2 on the CuO NW surfaces is successively achieved by atomic layer deposition, following which Ag nanoparticles (NPs) are deposited to synthesize a Ag-decorated CuO@TiO2 photocatalyst film. Microstructural and chemical analyses reveal uniform synthesis of a CuO@TiO2 heterojunction as well as a binding energy shift at the interface to form balanced Fermi energy, respectively. The performance of CuO@TiO2-Ag as a visible-light photocatalyst is evaluated under 20-W low-power visible-light LED illumination for the photodegradation of methylene blue. In addition, the effects of the TiO2 layer and the Ag NPs on the decomposition efficiency are investigated. To control the thickness of TiO2 and the dosage of Ag NPs, the photodegradation of CuO@TiO2-Ag is optimized at a rate of 0.0133 min−1, which is approximately 3 and 2.5 times higher than those of a bare CuO@TiO2 heterojunction and Ag-deposited CuO, respectively. The high decomposition efficiency achieved in this study results from the combined effects of the conformal core–shell heterojunction formed by atomic layer deposition and the well-distributed Ag NPs.

Experimental design, RSM and ANN modeling of tetracycline photocatalytic degradation using LDH@CN

The nano-photocatalyst of Cu-Al-Layered Double Hydroxide@Graphitic Carbon Nitride (LDH@CN NPC) was synthesized via a fast and cheap method, characterized, and applied for photocatalytic degradation of tetracycline (TC) antibiotic, as a model of main concern contaminant degradation under visible ray illumination and different conditions of initial TC concentration, irradiation time, photocatalyst dose and pH. The experimentally obtained results were modelled using the approaches of central composite design (CCD) and artificial neural network (ANN) to achieve a more accurate description of the process behaviour. Free radical trapping experiments verify that the holes and superoxide anion radicals were the main active species. Therefore, the high decomposition efficiency (96 %) where the parameters were 30 mgL−1, 7.18, 90 min, and 0.018 g of the mentioned variables, respectively, is attributed to the boosted in production of oxidants species through Z-scheme electron transfer heterojunction. The LC-Mass technique was also used to detect the intermediates and offer the proper pathway for photodegradation of TC. The favourable performance of this photocatalyst may be a promising step forward for prosperous large scale photodegradation of persistent organic pollutants in wastewater treatment plants. Evaluation of the developed models’ performance using several statistics showed a higher predictive capability of the ANN model. Comparison of photocatalytic performance of LDH@CN NPC with other recently developed counterparts highlighted its potential to be regarded as an alternative in the remediation of these categories of pollutants in water bodies.

Insights into highly effective catalytic persulfate activation on oxygen-functionalized mesoporous carbon for ciprofloxacin degradation.

Nanocarbons have been demonstrated as promising carbon catalysts for substituting metal-based catalysts for the green treatment of wastewater. In this study, oxygen-functionalized mesoporous carbon (OCMK-3) was prepared by wet oxidation and exhibited high catalytic performance against ciprofloxacin (CIP) by activation of persulfate. The effects of environmental parameters (pH, temperature, coexisting ions) and process parameters (temperature, sodium persulfate concentration, catalyst agent dosage, initial concentration) on the removal of CIP were investigated. Compared with the pristine ordered mesoporous carbon (CMK-3), the removal efficiency of CIP by OCMK-3 was increased by 32% under optimal conditions. This rise in activity was attributed to the increase in oxygen-containing functional groups, porosity, and specific surface area of OCMK-3 with improved structural defects and electron transfer efficiency. Furthermore, based on active species scavenging experiments, a dual-pathway mechanism of the radical and nonradical pathways was discovered. The rational degradation pathway of CIP was investigated based on liquid chromatography-mass spectrometry (LC-MS). In addition, the OCMK-3/PS system exhibited high decomposition efficiency in pharmaceutical wastewater treatment. This study provides an in-depth mechanism for the degradation of organic pollutants by carbon-based PS-AOPs and provides theoretical support for further studies.

Energy efficient treatment of indoor volatile organic compounds using a serial dielectric barrier discharge reactor

Volatile organic compounds (VOCs) generated in urban workplaces have been considered as significant air pollutants both indoors and outdoors. In order to reduce those harmful VOCs from urban emission sources, a non-thermal plasma reactor equipped with dielectric barrier discharge (DBD) using alternating current (AC) was investigated with a focus on process design including recirculation. Decomposition efficiency of low concentration VOCs was evaluated in terms of energy yield and conversion selectivity. At 20 ppm, the highest decomposition efficiency (97.3 %) was achieved in the treatment of n-hexane, followed by toluene at 96.6 %, MEK at 91.5 % and acetaldehyde at 90.4 %. A recirculation rate (QR) of 50 % improved the system efficiency, particularly for acetaldehyde (49.47 %–63.86 %) and toluene (79.05 %–95.89 %). It also increased the complete energy yield and the selectivity for carbon monoxide (CO) and carbon dioxide (CO2). By-product ozone concentration decreased significantly with increasing recirculation rate at the same input energy level.

Degradation of m-cresol over iron loaded carbon nanotube microfibrous composite: Kinetic optimization and deactivation study

Degradation of organic pollutant through catalytic wet peroxide oxidation (CWPO) is becoming more and more important in modern industry. As a commonly used organic synthetic material, excessive discharge of m-cresol may lead to severe damage of the environment and become a potential threat to human health. In this study, m-cresol was degraded over novel iron loaded carbon nanotube microfibrous composite (Fe-CNT-MF) catalyst packed fixed bed reactor. The kinetic parameters were first optimized, and then the deactivation mechanism of catalyst was also studied. The optimization model showed that total organic carbon (TOC) conversion of m-cresol degradation can reach about 70% under optimum conditions. Then the catalyst deactivation test was conducted with four consecutive runs (32 h in total). Fe-CNT-MF performed high m-cresol and TOC conversions (99% and 40%, respectively) as well as high H2O2 decomposition efficiency (100%) with no iron leaching. Besides, the effect of co-existing organic pollutants on m-cresol degradation was investigated with presence of 4-Ethylphenol and 2,5-dimethylphenol. Fe-CNT-MF exhibited good catalytic activity in multi-pollutant wastewater with 99% conversion for all pollutants. Finally, deactivation analysis results showed that the deactivation mechanism of Fe-CNT-MF included carbon deposition, surface property change and additional oxygen functionalities. A regeneration study was proceeded to further confirm the suggested mechanism, indicating that Fe-CNT-MF has a good regenerability.

Nonthermal plasma catalysis for toluene decomposition over BaTiO3-based catalysts by Ce doping at A-sites: The role of surface-reactive oxygen species

The insights on the primary surface-reactive oxygen species and their relation with lattice defects is essential for designing catalysts for plasma-catalytic reactions. Herein, a series of Ba1−xCexTiO3 perovskite catalysts with high specific surface areas (68.6–85.6 m2 g−1) were prepared by a facile in-situ Ce-doping strategy and investigated to catalytically decompose toluene. Combining the catalysts with a nonthermal plasma produced a significant synergy effect. The highest decomposition efficiency (100%), COx selectivity (98.1%), CO2 selectivity (63.9%), and the lowest O3 production (0 ppm) were obtained when BC4T (Ce/Ti molar ratio = 4:100) was packed in a coaxial dielectric barrier discharge reactor at a specific input energy of 508.8 J L−1. The H2-TPR, temperature-programmed Raman spectra, EPR and OSC results suggested that superoxides (•O2−) were the primary reactive oxygen species and were reversibly generated on the perovskite surface. Molecular O2 was adsorbed and activated at the active sites (Ti3+-VO) via an electron transfer process to form •O2−. Surface-adsorbed •O2− had a greater effect on the heterogeneous surface plasma reactions than the dielectric constant, and enhanced the toluene decomposition and intermediate oxidation. A possible reaction path of toluene decomposition was also proposed.

Decomposition of indoor VOC pollutants using non-thermal plasma with gas recycling

Volatile organic compounds in the indoor environment of small businesses (painting workshops, hair salons, nail shops, printing shops, laundries etc.) may result in adverse health effects for both workers and customers. Similarly, VOCs identified in these small businesses are included in the list of ozone precursors that harm the environment. We used a non-thermal plasma reactor with gas recycling to study the decomposition of dilute concentrations of VOCs in air. The non-thermal plasma reactor was a surface dielectric barrier discharge (surface DBD) type, and the target gases were methyl ethyl ketone, toluene and n-hexane at concentrations of 20, 50 and 100 ppmv. Highest decomposition efficiency (97%) was achieved by treating n-hexane at 20 ppmv. Gas recycling had an almost negligible effect during pollutant treatment at varying recycling rates (0-50%). Increasing the input energy resulted in higher decomposition efficiency, but had an inverse effect on the energy yield of the system. Concentrations of CO2 and ozone increased linearly with the increase of energy input in the system. Consumption of ozone for other applications, such as water treatment or coupling the DBD system with an appropriate catalyst, may address this concern.

Kinetics and reaction pathway of Aroclor 1254 removal by novel bimetallic catalysts supported on activated carbon

Bimetallic catalysts supported on activated carbon (AC) with high metal loadings were prepared by an ion-exchange method. AC-supported Ni-Cu, Ni-Zn and Ni-Pd bimetallic catalysts were used to decompose Aroclor 1254, which is one of the most commonly used commercial mix of polychlorinated biphenyls. Characterization by scanning electron microscopy and energy-dispersive X-ray analysis showed that the metals were uniformly distributed on the surfaces and inside the catalysts. The efficiencies of Aroclor 1254 decomposition were measured at different reaction temperatures and times. With increasing temperature, the catalytic activities increased and the activation energies of the reactions decreased, resulting in higher decomposition efficiencies. At 300 °C in a nitrogen atmosphere, Aroclor 1254 decomposition efficiencies of 99.3%, 99.4% and 99.5% were achieved for reactions with Ni-Cu/C, Ni-Zn/C and Ni-Pd/C, respectively. The kinetics and pathway of the decomposition reaction were discussed, and we concluded that the reactivity of the chlorine atoms located on the benzene rings followed the order para-position > meta-position > ortho-position. The PCBs were dechlorinated stepwise to form the final biphenyl product. The design concept and synthetic strategy developed in this study are of great significance in the disposal of chlorinated organic compounds, for use with the existing adsorption technology of AC.

Synthesis and Characterization of ZnS Quantum Dots on MnS2 Nanoparticles for Photo-assisted Electrochemical Degradation of Drug Compound

Herein, ZnS quantum dots on MnS2 (ZnS/MnS2) nanoparticles. Was prepared via the facile and simple method. The ZnS/MnS2 nanocomposites were characterized into attained optical, morphological, structural, and surface attributes using different analytical routs. The average crystallite size of MnS2 and ZnS/MnS2 nanocomposites are 27.2 and 14.8 nm via calculated from Scherrer’s equation. Subsequent, the photo-catalytic and -electrochemical attributes of synthesized ZnS/MnS2 nanocomposites were as well as presented. The ZnS/MnS2 nanocomposites electrode represented a potential influence on the decomposition of acetaminophen, which was higher than that of MnS2 nanoparticles electrode. The high amount of ZnS QDs in MnS2 samples has a high decomposition efficiency of acetaminophen due to the conduction band position and valence band position of ZnS QDs are higher than that of MnS2. Influencing major factors on the decomposition of acetaminophen were evaluated and the removal of acetaminophen was performed at pH:3, 60 mA cm− 2, and 0.1 M NaCl concentration. The prepared electrode represented great stability and indicated the highest possible for treatment technology of wastewater. Comparison of the performances of the photo-assisted electrochemical (PAEC) electrochemical (EC) and photo-catalytic indicated that the hybrid process (PAEC) has high efficiency for acetaminophen degradation.

Sparse decomposition method based on time–frequency spectrum segmentation for fault signals in rotating machinery

The impulse signal in large rotating machinery with damage fault is sparse, weak, coupled, and even nonperiodic in intermittent operation. To extract this complex signal is a key topic in machinery fault diagnosis. Sparse decomposition (SD) has excellent adaptability in describing arbitrary complex signals based on over-complete dictionary. However, the pursuit speed of best atom is a serious drawback. To alleviate this, a method of sparse decomposition based on time–frequency spectrum segmentation (SD-TFSS) is introduced. Generalized S transform (GST) provides the capability to show the distribution of vibration signals, but the resolution is susceptible to noise, multiresolution generalized S-transform (MGST) is developed to generate multiresolution time–frequency spectrums. Then, spectrums fusion with an appropriate threshold is adopted to acquire multiresolution binary spectrums and produce an optimal binary spectrum. From this optimal binary spectrum, all the connectivity areas are extracted and marked by spectrum segmentation. Thus, an optimal library can be constructed by selecting the optimal atoms of every connectivity area, and the signal can be expressed with this library. We conduct simulations and experiments demonstrating that the proposed method performs well with lower pursuit complexity, higher decomposition efficiency, and better approximation precision.

Strong piezo-electro-chemical effect of piezoelectric BaTiO3 nanofibers for vibration-catalysis

The piezo-electro-chemical effect, a phenomenon of vibration exciting chemical reaction, is hopeful for application in vibration-catalysis. In this work, BaTiO3 nanofibers were synthesized through an electrospinning method combined with a conventional sol-gel process. The piezo-electro-chemical effect of BaTiO3 nanofibers is realized through utilizing the product of piezoelectric effect and electro-chemical redox effect. BaTiO3 nanofibers behave a high vibration-catalytic decomposition efficiency of 97.5% for Rhodamine B dye within 60 min vibration. The piezo-electro-chemical intermediate product OH was observed in the vibration-catalytic process. The piezo-electro-chemical effect of BaTiO3 nanofibers is potential in utilizing vibration energy for dye wastewater treatment.

Co-Mn layered double hydroxide as an effective heterogeneous catalyst for degradation of organic dyes by activation of peroxymonosulfate

In this study, Co-Mn layered double hydroxide (Co-Mn LDH) was synthesized, characterized, and tested as heterogeneous catalyst to activate peroxymonosulfate (PMS) for degradation of organic dyes. The results of characterization showed that Co-Mn LDH had high purity, uniform morphology and large specific surface area (49.9379 m2/g). The degradation experiments demonstrated that five different dyes with the concentration of 50 mg/L could be decomposed completely within 240 s using only 0.025 g/L of Co-Mn LDH and 0.1 g/L of PMS. Moreover, Co-Mn LDH/PMS system presented the highest decomposition efficiency for acid orange G (AOG) compared with other related materials under the same condition. Further investigation found that Co-Mn LDH/PMS system had an excellent adaptability in a wide pH range (from 3 to 10), and the best efficiency was achieved when the solution was natural (pH = 6.87). The mineralization of AOG was assessed by Total Organic Carbon (TOC), and 52.2% of TOC was removed. Meanwhile, the good reusability and high stability of Co-Mn LDH were demonstrated by recycle tests and ion-leaching tests. The catalytic mechanism was explored through quenching tests as well as X-ray photoelectron spectroscopy (XPS) analysis. Finally, all of the results suggested that Co-Mn LDH/PMS system with high stability and decomposition efficiency was suitable for the remediation of organic dyes in wastewater.

Experimental Study on In-Situ Decomposition of VOCs Using Microwave-Induced Metal Discharge

In recent years, haze has become a critical environmental issue. As a crucial precursor of haze, volatile organic compounds (VOCs) have become a major research focus. In this study, microwave-induced metal discharge was developed for VOC decomposition. Toluene was used as the VOC model compound. Four types of metal strips were investigated for their decomposition efficiency of toluene using a microwave-induced metal discharge process. All discharges, regardless of the metal type, achieved a high decomposition efficiency of toluene [> 60% (mol/mol)]. In addition, the effects of reaction conditions such as metal strip weight, gas flow rate, microwave power, and gas initial concentration were studied to investigate the decomposition efficiency. The reaction conditions were optimized following a multi-factor orthogonal experiment. The weight of the metal strips and gas flow rate had greater impacts on the decomposition efficiency, whereas the microwave power had a moderate impact. The major reaction products were CO2, CO, O3 and H2O. Both hydroxyl radicals and active oxygen atoms were very important for toluene oxidation. This study offers an important reference for the development of new technology to support the decomposition of VOCs.

Enhanced activation process of persulfate by mesoporous carbon for degradation of aqueous organic pollutants: Electron transfer mechanism

Metal-free catalysis for green degradation of aqueous organic pollutants has caused extensive concern in recent years. In this study, hexagonally-ordered mesoporous carbon (CMK-3) was applied to activate persulfate (PS) for the degradation of 2,4-dichlorophenol (2,4-DCP) with superior removal rate of 90% in 20 min. The high catalytic efficiency was probably ascribed to the accelerated electron transfer resulting from the large adsorption capacity of CMK-3. It was found that specific surface areas (SSA), defective sites and functional groups on the activator were highly related to its catalytic efficiency and passivation. Compared to other nanocarbons, CMK-3 had better reusability due to its ordered mesoporous structure with large SSA and high defective degrees. For the first time, a two-pathway mechanism was proposed for metal-free activation process of PS, indicating that radical and non-radical oxidation worked together in PS activation for complete 2,4-DCP decomposition, and non-radical pathway played a dominant role while radical pathway was critical in accelerating the reaction. OH, SO4− and O2− all took part in the radical oxidation process, in which the contribution of OH was dominant. Besides, high decomposition efficiency was also achieved in pharmaceutical wastewater treatment by the CMK-3/PS system. This research proposed a new electron transfer mechanism for metal-free activation process of PS, which can provide a theoretical support for further studies.

Microwave Discharge Electrodeless Lamps (MDELs). Part XI. Photolytic, Chemical Oxidation, and Photocatalytic Treatment of Aqueous Urea Solution with a Novel MDEL Photoreactor.

Decomposition of urea in aqueous solution was carried out using a microwave discharge electrodeless lamp (MDEL) consisting of two photoreactors with a triple tube structure that generate vacuum-UV/UV light and reactive oxygen species (ROS) using microwaves (MW) as an energy source. The rate of decomposition of urea was highest under acidic conditions (pH 4) compared with those at pH 7 and 10. When used in combination with dispersed TiO2, a photocatalyst, high decomposition efficiency was achieved with less power consumption. Moreover, decomposition efficiency more than two times higher than that of ozone oxidation and sodium hypochlorite oxidation could be realized.