Design Of Photocatalytic Reactor Research Articles

Fe-doped TiO2/PVDF-HFP electrospun membranes for tetracycline photocatalytic degradation under visible light

Heterogeneous photocatalysis operated under visible light is considered an efficient and ecofriendly method to remove pharmaceuticals from water streams. However, the recovery of the nano-sized catalyst particles limits this technology to small-scale applications. In this study, we prepared Fe-doped P25 TiO2 photocatalysts and immobilized them over PVDF-HFP electrospun membranes for the photocatalytic degradation of Tetracycline antibiotic under visible light. To ensure uniform distribution of the nanoparticles on the fibers, the electrospinning voltage and the weight percentage of TiO2 were varied, and two preparation methods were applied to disperse the catalyst in the polymeric solution. In order to maximize the visible light exposure of the membranes, 3D printed membrane holders with square and circular shapes were designed to immerse the membrane in Tetracycline solution. The results showed that immobilizing P25 catalysts on the fibers of the membranes limited their visible light absorption when the light source was assembled on the top of the aqueous reaction medium. This occurred due to the membrane's opacity limited light penetration, resulting in uneven irradiation throughout its depth. Based on this, a new photocatalytic reactor design was proposed with immersed light illumination source to reduce the distance between the membrane and the light source for improved activation of the P25 particles. In this design, a 3D-printed vertical membrane holder was also included to accommodate a larger membrane surface area and therefore minimize the required spatial area for large industrial applications.

Photodriven Methane Conversion on Transition Metal Oxide Catalyst: Recent Progress and Prospects.

Methane as the main component in natural gas is a promising chemical raw material for synthesizing value-added chemicals, but its harsh chemical conversion process often causes severe energy and environment concerns. Photocatalysis provides an attractive path to active and convert methane into various products under mild conditions with clean and sustainable solar energy, although many challenges remain at present. In this review, recent advances in photocatalytic methane conversion are systematically summarized. As the basis of methane conversion, the activation of methane is first elucidated from the structural basis and activation path of methane molecules. The study is committed to categorizing and elucidating the research progress and the laws of the intricate methane conversion reactions according to the target products, including photocatalytic methane partial oxidation, reforming, coupling, combustion, and functionalization. Advanced photocatalytic reactor designs are also designed to enrich the options and reliability of photocatalytic methane conversion performance evaluation. The challenges and prospects of photocatalytic methane conversion are also discussed, which in turn offers guidelines for methane-conversion-related photocatalyst exploration, reaction mechanism investigation, and advanced photoreactor design.

The design of novel swash plate photocatalytic reactor with PAN/BiInOCl membrane photocatalyst for excellent RhB degradation

The low recovery efficiency and secondary pollution of traditional powder photocatalysts are the main problems restricting the practical application of photocatalysis technology. Therefore, PAN/BiInOCl membrane photocatalysts were prepared by simple electrospinning technology, and the swash plate photocatalytic reactor was designed according to the utilization characteristics of the membrane photocatalyst. By cooperating membrane photocatalyst with the swash plate photocatalytic reactor, the rapid and effective photocatalytic degradation of RhB simulated wastewater by PAN/BiInOCl membrane photocatalyst can be achieved, and the rapid and non-destructive recovery of photocatalysts can be realized. PAN/BiInOCl-3 membrane photocatalyst with the best photocatalytic degradation efficiency can realize the complete degradation of RhB within 30 min and has good stability under the actual sunlight irradiation. Radical trapping experiments confirmed that hydroxyl radicals and holes play a major role in the photocatalytic degradation of RhB. The preparation of PAN/BiInOCl membrane photocatalyst and the design of swash plate photocatalytic reactor lay a theoretical foundation for the design and preparation of efficient membrane photocatalyst and the application of photocatalytic technology in wastewater treatment.

Performance evaluation of a solar nano-photocatalytic reactor for wastewater treatment applications: Reaction kinetics, CFD, and scale-up perspectives

The solar-driven photocatalytic process, as a clean and efficient advanced oxidation process (AOP), is widely operated in wastewater treatment applications. In the present work, a solar nano photocatalytic reactor is designed, manufactured, and tested under different operating conditions. The irradiation-dependence reaction kinetics is studied in a batch operation process. A comprehensive computational fluid dynamics (CFD) model taking into account realistic solar flux distribution is developed and validated using experimental data. Finally, the reactor scaling-up analysis for higher treatment capacities is performed with the aim of the design of industrial-scale solar photocatalytic reactors. The research results indicate that when the initial dye concentration is increased from 5 to 175 mg/L, the period required to achieve 95% pollutant removal in 20 L solution and 10 mg/L photocatalyst concentration boosts up to 2.2 times. When the photocatalyst concentration in the solution is increased from 5 to 20 mg/L, the time required to achieve 95% total removal is reduced to 35.7%. For the photocatalyst concentration of 75 mg/L compared to 20 mg/L, the time required for 95% degradation increases up to 16.7%. To treat 90% of the total pollutant in a 50 mg/L dye solution with an initial volume of 5 m3 and using 20 mg/L photocatalyst concentration under 11 h operation with an average solar irradiation intensity of 750.46 W/m2, a solar reactor with a surface area of 50.45 m2 is required, while for 10 m3 wastewater sample and the same conditions and 95% pollutant removal, the collector area is obtained to be 121.36 m2. A horizontal solar reactor compared to its optimal tilt angle can reduce the treatment capacity up to 55%.

Numerical Simulation of Energy and Mass Transfer in a Magnetic Stirring Photocatalytic Reactor

Hydrogen production via photocatalytic water splitting is one of the promising solutions to energy and environmental issues. Understanding the relationship between hydrogen production in suspended photocatalytic reactions and various influencing factors is crucial for expanding the scale of the system. However, the complexity of physical and chemical factors involved in hydrogen production via photocatalytic water splitting makes systematic research of this technology challenging. In recent research, the simulated light source reactor has become a preferred study object due to its strong controllability. This paper presents a comprehensive energy and mass transfer model for the suspended photocatalytic reaction in a magnetically stirred reactor. The mutual impacts between the flow field, radiation field, and reaction field are analyzed. The simulation results show that the rotating speed of the stirring magneton in the reactor has a significant influence on the flow field. The rotation of the stirring magneton generates a vortex in the central axis area of the reactor, with the relationship between the depth of the vortex f(s) and the rotating speed of the magneton s described as f(s) = 0.27e0.0032s. The distribution of radiation within the reactor is influenced by both the incident radiation intensity and the concentration of the catalyst. The relationship between the penetration depth of radiation g(i) and the incident radiation intensity i is described as g(i) = 10.73ln(i) − 49.59. The relationship between the penetration depth of radiation h(c) and the particle concentration c is given as h(c) = −16.38ln(c) + 15.01. The radiation distribution in the reactor has a substantial impact on hydrogen production, which affects the concentration distribution law of hydrogen. The total amounts of hydrogen generated in the reactor are 1.04 × 10−3 mol and 1.35 × 10−3 mol when the reaction times are 1.0 s and 2.0 s, respectively. This study serves as a foundation for the future scaling of the system and offers theoretical guidance for the optimization of the photocatalytic reactor design and operating conditions.

Glass tube-coated TiO2 nanostructure for degradation of methylene blue: an experimental and design of column photocatalytic reactor

This work presents the successfully of TiO2 nanostructure synthesis using manual grinding combined hydrothermal method for photocatalyst. XRD confirmed that TiO2 was arranged by anatase and rutile phase with crystal size of 18.54 nm. Characterization of digital microscope shows the spread of catalyst on the glass tube surface, which can be observed furthermore using interactive 3D surface plot. Band gap energy determination from UV-Vis spectroscopy scanning shows the minimum energy that is required to facilitate electron-hole generated. In 20 min of irradiation, TiO2 existence can completely decompose MB (100%) that can be presented by TiO2 absence. Degradation of MB is higher effective in acidic condition which optimum pH of 5. Using first order reaction, glass tube-coated TiO2 has rate constant of 0.2102 min-1, 1.5 times faster than bare glass tube. This enhancement proves that the designed reactor has good prospect for organic pollutant treatment. Moreover, compared with other reported study, this system provides relatively more effective of MB photodegradation.

Optimal design of novel honeycomb photocatalytic reactors for numerical analysis of formaldehyde degradation by CFD modeling

As an alternative to the investigation of photocatalysts, it is a potential approach to enhance the photocatalytic performance of the novel photocatalytic reactor by optimizing its geometric structure and reaction conditions. In this work, five different honeycomb photocatalytic reactors with a deflector and a porous airflow distribution plate were designed and a numerical simulation was performed based on computational fluid dynamics (CFD). The simulation results showed that a huge vortex appeared near the entrance of the original model and the velocity distribution inside the reactor was non-uniform, whereas these shortcomings could be effectively overcome when using the 45° deflector model (S-4) compared to the other models. Compared to S-1, the photocatalytic conversion rate of formaldehyde for S-4 was boosted by 7.29% at a flow velocity of 0.04 m s−1. In addition, it was found that the photocatalytic conversion rate of formaldehyde increased from 55.45 to 94.73% when the velocity decreased from 0.04 to 0.01 m s−1, and the photocatalytic removal rate of formaldehyde decreased from 94.73 to 70.05% as the relative humidity varied from 20 to 70%. Furthermore, when the irradiance increased from 45 to 265 mW cm−2, the photocatalytic conversion rate of formaldehyde improved by 10.78%. Overall, this work contributes to the design of the novel honeycomb reactor to acquire the optimized construction of the photocatalytic reactor.

Continuous-flow reactor with superior production rate and stability for CO2 reduction using semiconductor photocatalysts

A new semiconductor-based photocatalytic reactor design with optimized pressure and flow rates on both sides of an intermediately placed catalyst enhances mass transport, accelerates CO desorption and prevents photocatalyst deactivation.

3D bionic reactor optimizes photon and mass transfer by expanding reaction space to enhance photocatalytic CO2 reduction

Use of 3D photocatalytic reactor has been widely explored for development of efficient photocatalytic systems. In the present study, a bionic palisade cells BiOBr/Sr2Nb2O7/Al6Si2O13 photocatalytic reactor with high strength was prepared through combination of 3D printing technology and solvothermal method. The carefully designed and optimized bionic palisade cell structure exhibited a periodic porous structure with high surface area. The controllable periodic structure effectively regulated the internal photon transfer and mass transfer. Photon transfer ensured that light is fully scattered within the structure, which improved light utilization. High mass transfer ensured smooth flow of reactant inside the structure, which increased reactant adsorption on the surface of photocatalysts. The interface electric field of the BiOBr/Sr2Nb2O7 p-n heterojunction effectively separated the photogenerated electrons and holes. The BOB/SNO/ASO structure had high photocatalytic CO2 reduction performance under the simulated sunlight. The CO yield for the reaction was 13.68 μmol/g/h, whereas that of CH4 yield was 6.37 μmol/g/h. Therefore, the findings of the present study provide a basis for design and preparation of high-performance 3D photocatalytic reactors.

Recent Advances in Photocatalytic Removal of Microplastics: Mechanisms, Kinetic Degradation, and Reactor Design

Plastic products are used in almost all aspects of our daily life. Due to their low cost, portability, durability, and resistance to degradation, these products are affecting the health of the environment and biota on a global scale. Thus, the removal and mineralization of microplastics is an important challenge in the 21st century. Advanced oxidation processes (AOPs) have recently been identified as a viable treatment technique for tackling recalcitrant organic molecules and polymers. However, information on kinetic degradation mechanisms and photocatalytic reactor design is insufficient. This review discusses the fundamentals of photocatalysis and photo-Fenton processes in addition to the photocatalytic degradation mechanisms. We also introduce different characterization techniques of the major microplastic pollutants such as PE, PP, PVC, PS, PMMA, and PA66. In addition, a detailed overview of the major existing photocatalytic plants and the scaling-up methods of photoreactors are discussed.

Interdependence of Kinetics and Fluid Dynamics in the Design of Photocatalytic Membrane Reactors.

Photocatalytic membrane reactors (PMRs) are a promising technology for wastewater reclamation. The principles of PMRs are based on photocatalytic degradation and membrane rejection, the different processes occurring simultaneously. Coupled photocatalysis and membrane filtration has made PMRs suitable for application in the removal of emerging contaminants (ECs), such as diclofenac, carbamazepine, ibuprofen, lincomycin, diphenhydramine, rhodamine, and tamoxifen, from wastewater, while reducing the likelihood of byproducts being present in the permeate stream. The viability of PMRs depends on the hypotheses used during design and the kinetic properties of the systems. The choice of design models and the assumptions made in their application can have an impact on reactor design outcomes. A design’s resilience is due to the development of a mathematical model that links material and mass balances to various sub-models, including the fluid dynamic model, the radiation emission model, the radiation absorption model, and the kinetic model. Hence, this review addresses the discrepancies with traditional kinetic models, fluid flow dynamics, and radiation emission and absorption, all of which have an impact on upscaling and reactor design. Computational and analytical descriptions of how to develop a PMR system with high throughput, performance, and energy efficiency are provided. The potential solutions are classified according to the catalyst, fluid dynamics, thickness, geometry, and light source used. Two main PMR types are comprehensively described, and a discussion of various influential factors relating to PMRs was used as a premise for developing an ideal reactor. The aim of this work was to resolve potential divergences that occur during PMRs design as most real reactors do not conform to the idealized fluid dynamics. Lastly, the application of PMRs is evaluated, not only in relation to the removal of endocrine-disrupting compounds (EDCs) from wastewater, but also in dye, oil, heavy metals, and pesticide removal.

Glass coated-nanostructure semiconductor TiO2/RGO/MoS2 for dye removal and disinfection of wastewater: Design and construction of a novel fixed-bed photocatalytic reactor

In the field of applied semiconductor, TiO2/RGO/MoS2 nanocomposite as a high performance photocatalyst has been synthesized. Prepared semiconductor has been coated on borosilicate glass rods with a facile one pot process and imbedded in the photoreactor chamber. Fabrication and presentation of an appropriate photoreactor for effective wastewater treatment has been developed. In this photoreactor continuous air by producing bubbles provides an effective mixing of the target solution. The performance of the designated system has been examined by investing the photocatalytic degradation of rhodamine B (RhB) and was more than 95% dye removal. Electrochemical investigation (Mott-Schottky, Nyquist and Bode plots) showed that long electron lifetime of TiO2/RGO/MoS2 is the main reason for high photoactivity of this nanocomposite. Optimization of the different parameters such as influence of bubbling and light intensity of the photoreactor, the initial pH and the initial concentration of RhB on the photocatalytic performance have been also studied. TOC of the reaction were conducted which showed good mineralization. The photocatalyst powder was characterized by BET, BJH, SEM, EDX, FT-IR, XRD, EIS, and ICP-OES. Low leaching has been confirmed by ICP investigation. Photocatalytic treatment of liquorice factory wastewater in several concentrations has been also studied. Disinfection capability of TiO2/RGO/MoS2, in designated system for liquorice factory wastewater has been investigated. This system is so effective to eliminate harmful microorganisms. Total coliform for liquorice factory wastewater with a 21000 MPN/100 before treatment reached to zero MPN/100 after treatment in optimum reaction conditions.

Photocatalytic reactor design and its application in real wastewater treatment using TiO2 coated on the stainless-steel mesh.

The application of wastewater treatment using TiO2 coated on the stainless-steel mesh is promising for disintegrating organic pollutants in wastewater. This research successfully coated TiO2 particles on stainless-steel mesh for the photocatalyst process by using the dip-coating method. This method was selected due to its simplicity and low cost, as well as its extensive application prospects in wastewater treatment. The photocatalytic oxidation of real wastewater treatment was developed and designed for a photo-reactor in terms of flow rate (varied on 2.0-4.0 L/min) and light distance (varied on 5.0-15.0cm), whereas the preparation of the material process was investigated in terms of TiO2 catalyst dosage (varied on 1.0-3.0g) and layers of coating (varied on 1 to 3 layers). Experiments were employed to degrade organic wastewater from methylene blue (MB) for a prelim experiment and real wastewater effluent testing for the application. The optimized TiO2 dosage was 2.0g with 2 layers of coating coated on the stainless-steel mesh. The designed photo-reactor was optimized with a flow rate of 2.0 L/min and a light distance of 10.0cm to treat the organic pollutants in raw domestic wastewater effluent on photocatalytic activity. MB successfully degraded about 96% in 3h under UV-C irradiation after adsorption equilibrium was completed (3h), whereas the efficiency of BOD removal was 89% under UV-C irradiation in 4h. Therefore, TiO2 (2.0g) coated on stainless-steel mesh with 2 layers of the coating prepared by dip-coating is a potentially effective alternative for real wastewater treatment.

Synthesis and Performance of Photocatalysts for Photocatalytic Hydrogen Production: Future Perspectives

Photocatalysis for “green” hydrogen production is a technology of increasing importance that has been studied using both TiO2–based and heterojunction composite-based semiconductors. Different irradiation sources and reactor units can be considered for the enhancement of photocatalysis. Current approaches also consider the use of electron/hole scavengers, organic species, such as ethanol, that are “available” in agricultural waste, in communities around the world. Alternatively, organic pollutants present in wastewaters can be used as organic scavengers, reducing health and environmental concerns for plants, animals, and humans. Thus, photocatalysis may help reduce the carbon footprint of energy production by generating H2, a friendly energy carrier, and by minimizing water contamination. This review discusses the most up-to-date and important information on photocatalysis for hydrogen production, providing a critical evaluation of: (1) The synthesis and characterization of semiconductor materials; (2) The design of photocatalytic reactors; (3) The reaction engineering of photocatalysis; (4) Photocatalysis energy efficiencies; and (5) The future opportunities for photocatalysis using artificial intelligence. Overall, this review describes the state-of-the-art of TiO2–based and heterojunction composite-based semiconductors that produce H2 from aqueous systems, demonstrating the viability of photocatalysis for “green” hydrogen production.

Modelling and simulation of a photocatalytic reactor at high TiO2 concentrations

AbstractThis work presents a model of an annular batch slurry photocatalytic reactor using titanium dioxide at high concentrations and pH close to 7. The model considers the effects of the agglomeration of catalyst particles that take place when the reactor operates close to neutral pH. It also includes the adsorption/desorption equilibrium of the contaminant on the catalyst during 1 h in darkness, followed by the photochemical reaction under UV irradiation. The reactor was modelled by a system of differential equations solved using the Micro‐Cap 12 program. This powerful software package numerically solves the differential equations as an equivalent network, providing a convenient graphical interface for model programming and plotting of results. The model was validated with measurements at several catalyst concentrations from 1–2.5 g/L. Aeroxide P25, supplied by Evonik, was used as catalyst, with UV irradiation at a wavelength of 254 nm. Orange II, a widely used azo dye, was chosen as the model contaminant. The model results were in satisfactory agreement with the experimental data. Simulations were carried out with different initial conditions, to analyze the influence of the system variables on the performance of the reactor. In this way, the optimal design criteria at high catalyst concentrations were found. The mathematical model is simple and robust and can be applied in a straightforward way to the design and scaling of photocatalytic reactors. It is also particularly attractive for educational purposes.

Toward Scaling-Up Photocatalytic Process for Multiphase Environmental Applications

Recently, we have witnessed a booming development of composites and multi-dopant metal oxides to be employed as novel photocatalysts. Yet the practical application of photocatalysis for environmental purposes is still elusive. Concerns about the unknown fate and toxicity of nanoparticles, unsatisfactory performance in real conditions, mass transfer limitations and durability issues have so far discouraged investments in full-scale applications of photocatalysis. Herein, we provide a critical overview of the main challenges that are limiting large-scale application of photocatalysis in air and water/wastewater purification. We then discuss the main approaches reported in the literature to tackle these shortcomings, such as the design of photocatalytic reactors that retain the photocatalyst, the study of degradation of micropollutants in different water matrices, and the development of gas-phase reactors with optimized contact time and irradiation. Furthermore, we provide a critical analysis of research–practice gaps such as treatment of real water and air samples, degradation of pollutants with actual environmental concentrations, photocatalyst deactivation, and cost and environmental life-cycle assessment.

Design and optimisation of a low-cost titanium dioxide-coated stainless steel mesh photocatalytic water treatment reactor

Photocatalysis has been extensively studied in recent years for environmental wastewater treatment applications. Although promising, it has yet to be globally adopted, as it faces many challenges; namely cost, complexity and efficiency. This present work focuses on the optimisation of a bespoke photocatalytic water treatment reactor. Contrary to other studies, the reactor was exclusively built from inexpensive and readily available consumer market parts, to facilitate a widespread adoption of this water treatment method. Photocatalytic TiO2 was synthesised and immobilised on stainless steel woven mesh in a one-step process, via reactive pulsed DC magnetron sputtering. A two-levels augmented screening design template was used to optimise the performance of the bespoke photocatalytic reactor, consisting of 20 experimental runs. Five independent variables were studied, UV light intensity, number of TiO2-coated mesh layers, coating thickness, water flowrate and initial dye concentration. Methylene blue dye solution was used as a model pollutant and the removal percentage after 5 h was used as a response. A linear regression model was built from the experimental results and revealed that all first-order terms, with the exception of flowrate, were significant contributors to the model pollutant removal. Increasing the coating thickness and the number of TiO2-coated mesh layers did improve the removal rate of methylene blue. These benefits cancelled each other when both variables were at their highest levels, due to a decreased light permeability through the mesh. ANOVA, lack-of-fit, and R2 analysis confirmed the significance of the linear regression model. Optimised conditions were identified, leading to the removal of more than 90% of the model pollutant after 5 h of UV-A illumination. The calculated pseudo-first-order constant was as high as 14.5 × 10−5 s−1, while the quantum yield was estimated to be 4.22 × 10−6 molecules/photons and the figure of merit was calculated at 1.14. This substrate/catalyst combination proved to be effective at degrading methylene blue, with no evident performance degradation after 10 repeated cycles, equivalent to 360 h of consecutive use. This present work demonstrates that it is possible to build an efficient photocatalytic reactor from inexpensive computer enthusiast parts, combined with a highly scalable and industry friendly photocatalyst production technique.

Computer Simulations of Photocatalytic Reactors

Photocatalysis has been considered future technology for green energy conversion and environmental purification, including carbon dioxide reduction, water splitting, air/water treatment, and antimicrobial purposes. Although various photocatalysts with high activity and stability have already been found, the commercialization of photocatalytic processes seems to be slow; it is thought that the difficulty in scaling up photocatalytic processes might be responsible. Research on the design of photocatalytic reactors using computer simulations has been recently intensive. The computer simulations involve various methods of hydrodynamics, radiation, and mass transport analysis, including the Monte Carlo method, the approximation approach–P1 model, and computational fluid dynamics as a complex simulation tool. This review presents all of these models, which might be efficiently used for the scaling-up of photocatalytic reactors. The challenging aspects and perspectives of computer simulation are also addressed for the future development of applied photocatalysis.

Photocatalytic Inactivation as a Method of Elimination of E. coli from Drinking Water

The presence of microorganisms, specifically the Escherichia coli, in drinking water is of global concern. This is mainly due to the health implications of these pathogens. Several conventional methods have been developed for their removal; however, this pathogen is still found in most drinking water. In the continuous quest for a more effective removal approach, photocatalysis has been considered as an alternative method for the elimination of pathogens including E. coli from water. Photocatalysis has many advantages compared to the conventional methods. It offers the advantage of non-toxicity and utilizes the energy from sunlight, thereby making it a completely green route. Since most photocatalysts could only be active in the ultraviolet region of the solar spectrum, which is less than 5% of the entire spectrum, the challenge associated with photocatalysis is the design of a system for the effective harvest and complete utilization of the solar energy for the photocatalytic process. In this review, different photocatalysts for effective inactivation of E. coli and the mechanism involved in the process were reviewed. Various strategies that have been adopted in order to modulate the band gap energy of these photocatalysts have been explored. In addition, different methods of estimating and detecting E. coli in drinking water were presented. Furthermore, different photocatalytic reactor designs for photocatalytic inactivation of E. coli were examined. Finally, the kinetics of E. coli inactivation was discussed.

Advances in engineered design and performance of photocatalytic membrane reactor for polluted water treatment

Advances in engineered design and performance of photocatalytic membrane reactor for polluted water treatment