Photoreactor Configuration Research Articles

Effect of Photoreactor Design on the Degradation of Thiamethoxam by Pure/Supported Titanium Dioxide

The environmental persistence of thiamethoxam (THX), a commonly used neonicotinoid insecticide, raises concerns about its long-term effects. This study explored the photocatalytic degradation of THX using pure and perlite supported TiO<sub>2</sub> photocatalysts in two distinct UV photoreactor configurations. Our investigation aimed to identify some optimal conditions for efficient THX removal while considering cost-effectiveness and sustainability for potential industrial applications. The results revealed that horizontal UV irradiation (System 1) significantly surpassed vertical irradiation (System 2) in both THX degradation rate and energy efficiency. This highlights the importance of photoreactor design for maximizing light utilization and mass transfer. While pure TiO<sub>2</sub> exhibited superior performance in both systems compared to perlite-supported TiO<sub>2</sub> (PST), the latter demonstrated an intriguing temperature dependence. PST achieved enhanced degradation at higher temperatures, suggesting its potential for industrial applications where waste heat is available. Furthermore, we discovered that low pH conditions substantially boosted THX degradation with PST, opening a promising avenue for optimizing industrial processes and minimizing chemical usage. This finding underscores the crucial role of operational parameters in tailoring photocatalytic performance. In conclusion, this study provided strong evidence for the effectiveness of TiO<sub>2</sub> photocatalysis in degrading THX, a persistent organic pollutant. We emphasized the impact of catalyst support, photoreactor design, and operational parameters, such as temperature and pH, on treatment efficiency. Notably, the enhanced performance of PST at higher temperatures and its responsiveness to low pH conditions suggest its potential for cost-effective and sustainable THX treatment in industrial settings. These findings pave the way for further research and development of optimized photocatalytic systems for mitigating environmental contamination by THX and other persistent organic pollutants.

Modeling and simulation of reactors for methanol production by CO2 reduction: A comparative study

The extensive utilization of fossil fuel energy has caused severe degradation to our environment, therefore the search for new clean efficient energy is the need of the hour. Photocatalytic conversion of CO2 to solar fuels, and artificial photosynthesis, offer a promising solution for the energy crisis and global warming. Improving efficiency in the photo-reduction of CO2 to fuels involves developing highly efficient catalysts and optimizing photoreactor configuration. Photocatalysis is a process in which light radiations having energy equal to or greater than the band gap energy (Ebg) of a semiconductor strikes on its surface and generates electron (e−) hole(h+) pairs. The photogenerated electrons and holes participate in various oxidation and reduction processes to produce final products. This field focuses on harnessing solar energy to drive the conversion of carbon dioxide into hydrocarbon fuels, showcasing significant potential for sustainable energy solutions. The global methanol market was valued at $30.9 billion in 2023 and is projected to reach $38 billion by 2028, growing at 4.2 % CAGR during the forecast period. For determining the feasibility of reactions on a larger scale, simulations must be performed at different conditions for obtaining higher conversion and cost-effective management of the process at the industrial level. So, a simulation of methanol photoreactors using different software was done to examine the kinetics of methanol reactors by employing ASPEN, DWSIM, and MATLAB software for simulating experimental data.

Comprehensive evaluation of a novel pilot-scale UVA-LED photoreactor for water treatment applications: Characterization, catalytic efficiency, energy performance and economic viability

A comprehensive assessment was conducted on a novel pilot plant employing a tubular photo-reactor configuration integrated with UVA-LED technology for advanced municipal wastewater treatment applications. The plant consists of eight UVA-LED strips (150 LEDs/strip, 348–400 nm with peak emission at 370 nm) achieving a maximum irradiance of 28.1 W/m2 at 100 % power of the LED, symmetrically distributed across two borosilicate tubes. The iron concentration (0.025–0.100 mM) and UVA-LED irradiance (1.4–28.1 W/m2) combined effect on the photo-Fenton process efficiency was thoroughly examined in synthetic tap water and synthetic municipal wastewater treatment plant (MWWTP) secondary effluent using sulfamethoxazole as model microcontaminant. In general, an LED intensity threshold from which process efficiency reaches a plateau maximum value was found. The determination of the electrical energy per order (EEO) showed higher energy efficiencies as LED intensity decreases, iron concentration increases, and the water matrix is simpler. The lowest EEO obtained was 0.009 kWh/m3·order for 0.10 mM iron concentration in synthetic MWWTP secondary effluent at 5 % LED intensity. The economic study revealed that the weight of operating costs is more significant than the weight of investment costs, regardless of the selected operating conditions. Working with an iron concentration of 0.10 mM helps reduce the total costs, while operating either under excess LED intensity or insufficient LED intensity negatively impacts the total treatment cost. The lowest treatment cost (0.19 €/m3) was obtained with 0.10 mM iron concentration at only 10 % LED intensity. A comparison with the same process driven by natural solar radiation in a raceway pond reactor demonstrated the feasibility of the novel photo-reactor design in terms of treatment cost.

UV-induced simultaneous oxidation/reduction of cefixime and chromium

This study explores a novel approach utilizing a UV-based photo-removal process to simultaneously eliminate organic (Cefixime-CFX) and inorganic (chromium) pollutants from wastewater. The photoreactor's configuration, segregating wastewater inlets and outlets, facilitates efficient removal. The study investigates the effect of various parameters such as pH, CFX:Cr molar ratio, and kinetic models on the removal efficiency.Analytical methods involve high-performance liquid chromatography for CFX concentration determination and atomic absorption for chromium measurement. Results showed that higher pH levels favored enhanced photo-removal of both compounds, with pH 9 displaying optimal removal efficiencies of 100 % for CFX and 46.7 % for chromium. The CFX/Cr molar ratio of 20:1 exhibited superior removal rates, achieving approximately 100 % CFX and 82.3 % chromium removal within 25 min. Additionally, kinetic analyses indicated the importance of pH in accelerating organic breakdown and subsequent production of reducing and oxidizing species, facilitating chromium precipitation. Effluent toxicology tests using the Kirby & Bauer method indicate a significant reduction in toxicity over time, suggesting the suitability of the effluent for discharge into the environment. Additionally, sludge analysis through FTIR identifies various chromate species produced during the photo-removal process, contributing to a comprehensive understanding of sludge composition. The investigation demonstrates that the UV-based photo-removal process efficiently removes both organic and inorganic pollutants while minimizing energy consumption and avoiding the formation of hazardous secondary intermediates. This study provides insights into a sustainable and effective method for wastewater treatment, with potential applications in environmental protection and pollution control.

A Brief Review of Photocatalytic Reactors Used for Persistent Pesticides Degradation

Pesticide pollution is a major issue, given their intensive use in the 20th century, which led to their accumulation in the environment. At the international level, strict regulations are imposed on the use of pesticides, simultaneously with the increasing interest of researchers from all over the world to find methods of neutralizing them. Photocatalytic degradation is an intensively studied method to be applied for the degradation of pesticides, especially through the use of solar energy. The mechanisms of photocatalysis are studied and implemented in pilot and semi-pilot installations on experimental platforms, in order to be able to make this method more efficient and to identify the equipment that can achieve the photodegradation of pesticides with the highest possible yields. This paper proposes a brief review of the impact of pesticides on the environment and some techniques for their degradation, with the main emphasis on different photoreactor configurations, using slurry or immobilized photocatalysts. This review highlights the efforts of researchers to harmonize the main elements of photocatalysis: choice of the photocatalyst, and the way of photocatalyst integration within photoreaction configuration, in order to make the transfer of momentum, mass, and energy as efficient as possible for optimal excitation of the photocatalyst.

Performance of a C-containing Cu-based photocatalyst for the degradation of tartrazine: Comparison of performance in a slurry and CPC photoreactor under artificial and natural solar light

A carbon-containing Cu-based material (Cu@C) was used as photocatalyst for the degradation of a commonly food-industry azo-dye (tartrazine, also called Y5), under solar light at laboratory and pilot scale photoreactors. Important performance parameters such as dark adsorption capacity, catalyst́s loading and initial concentration of the dye were first optimized in a slurry photoreactor at laboratory scale under artificial solar light following the kinetics of degradation of the dye. Afterwards, the photocatalytic activity was investigated at pilot scale in a compound parabolic collector (CPC) photoreactor operating for 10 h of irradiation. The degradation of tartrazine is among the highest values reported for alternative metal oxide semiconductors, in both photoreactor configurations. Catalytic data revealed a 3 times faster degradation kinetics of tartrazine in the CPC photoreactor under natural solar light than in the slurry reactor under artificial solar light. This behavior indicates that a moderate photon flux in the CPC is more adequate to operate with the prepared photocatalyst, as it minimizes the recombination of charge carriers in the catalyst. This is important, since most of the photocatalytic tests designed to evaluate the activity of novel materials are frequently carried out under simulated solar light and disregard the impact of photon flux in outdoor conditions.

Scalable Photocatalyst Panels for Photoreforming of Plastic, Biomass and Mixed Waste in Flow.

Solar-driven reforming uses sunlight and a photocatalyst to generate H2 fuel from waste at ambient temperature and pressure. However, it faces practical scaling challenges such as photocatalyst dispersion and recyclability, competing light absorption by the waste solution, slow reaction rates and low conversion yields. Here, the immobilisation of a noble-metal-free carbon nitride/nickel phosphide (CNx |Ni2 P) photocatalyst on textured glass is shown to overcome several of these limitations. The 1 cm2 CNx |Ni2 P panels photoreform plastic, biomass, food and mixed waste into H2 and organic molecules with rates comparable to those of photocatalyst slurries. Furthermore, the panels enable facile photocatalyst recycling and novel photoreactor configurations that prevent parasitic light absorption, thereby promoting H2 production from turbid waste solutions. Scalability is further verified by preparing 25 cm2 CNx |Ni2 P panels for use in a custom-designed flow reactor to generate up to 21 μmolH m-2 h-1 under "real-world" (seawater, low sunlight) conditions. The application of inexpensive and readily scalable CNx |Ni2 P panels to photoreforming of a variety of real waste streams provides a crucial step towards the practical deployment of this technology.

Photoproduction of hydrogen in microreactors: Catalytic coating or slurry configuration?

A quartz microreactor containing 28 microchannels of 500 μm width and 105 mm length has been used to photoproduce hydrogen from liquid water-ethanol using an Au/TiO2 photocatalyst and UV light. The photomicroreactor has been tested in two flow configurations: (i) as a catalytic wall photoreactor by coating the microchannels with the photocatalyst, and (ii) as a slurry photoreactor by dispersing the photocatalyst in the liquid mixture of water-ethanol. The catalytic wall photoreactor configuration shows superior performance, with hydrogen yields more than three times higher than those obtained with the best slurry configuration under the same operation conditions.

A MATLAB-Based Application for Modeling and Simulation of Solar Slurry Photocatalytic Reactors for Environmental Applications

Because of the complexity caused by photochemical reactions and radiation transport, accomplishing photoreactor modeling usually poses a barrier for young researchers or research works that focus on experimental developments, although it may be a crucial tool for reducing experimental efforts and carrying out a more comprehensive analysis of the results. This work presents PHOTOREAC, an open-access application developed in the graphical user interface of Matlab, which allows a user-friendly evaluation of the solar photoreactors operation. The app includes several solar photoreactor configurations and kinetics models as well as two variants of a radiation absorption-scattering model. Moreover, PHOTOREAC incorporates a database of 26 of experimental solar photodegradation datasets with a variety of operational conditions (model pollutants, photocatalyst concentrations, initial pollutant concentrations); additionally, users can introduce their new experimental data. The implementation of PHOTOREAC is presented using three example cases of solar photoreactor operation in which the impact of the operational parameters is explored, kinetic constants are estimated according to experimental data, and comparisons are made between the available models. Finally, the impact of the application on young researchers’ projects in photocatalysis at the University of Cartagena was investigated. PHOTOREAC is available upon request from Professor Miguel Mueses.

Main parameters influencing the design of photocatalytic reactors for wastewater treatment: a mini review

AbstractThe research in the heterogeneous photocatalysis to remove different types of pollutants in liquid phase has notably increased in the last years. The main objectives of the research dealing with photocatalysis were: (i) to shift the photoactivity of catalysts in the visible light range or to increase the degradation rate; (ii) the use of the artificial light sources (low pressure lamp, high pressure lamp, LEDs, and optical fibers) and solar light; (iii) photocatalysts recovering and deactivation; (iv) photoreactor configuration; (v) photodegradation of contaminants of emerging concern; and (vi) verification of induced effects from the photocatalytic treatment, such as the induction of bacterial resistance. Here, one of the main problems in the practical application of photocatalysis, which is the photoreactors scale‐up, is addressed with the use of mathematical modeling. In this perspective, this mini review reports a literature exam of the main parameters that are important to take into account for the design and the development of photoreactors for wastewater treatment, and through the use of computational fluid dynamics models (CFD). © 2020 Society of Chemical Industry

High-radiance LED-driven fluidized bed photoreactor for the complete oxidation of n-hexane in air

This work presents a highly efficient photo-reactor configuration for VOC abatement. It consists of a fluidized bed made of commercial, easy to fluidize, transparent borosilicate glass beads coated with commercial TiO2 nanoparticles (0.15–2.3 wt% loadings). Herein, we demonstrate that the use of high-radiance/low consumption UV-LEDs as irradiation sources with a deeper light penetration under fluidizing conditions facilitates the photocatalytic response to achieve the complete oxidation of VOCs. The role of different parameters such as catalyst loading and irradiation power have been thoroughly studied and evaluated to maximize the full combustion of n-hexane. Under the high radiance (up to 2200 mW/cm2) conditions used the bed heats significantly (up to 190 °C), although this did not have an effect on the conversions reached, which depended solely on the wavelength and power used. The productivity of the photoreactor tested and the space velocity used were around 5.25 × 10−2 mol/g·h and 12000 h−1 respectively.

Sunfuels from CO2 exhaust emissions: Insights into the role of photoreactor configuration by the study in laboratory and industrial environment

Direct photoconversion of CO2 from exhaust emissions into fuels and chemicals is one of the most ambitious challenges to a greater and more effective use of the solar source. Through an extensive and systematic evaluation of CO2 photoreduction process, both in aqueous media and in gas-vapour stream for over 120 h, this work addresses the role of the photoreactor configuration on the CO2 reduction efficiency, leading the study from laboratory to industrial environment, probably for the very first time. Therefore, the performance of a continuously stirred “semi-batch” (SB) photoreactor, a packed-bed (PB) photoreactor and a multi-tubular (MT) photoreactor has been compared in term of efficiency, products distribution and available energy. The results of the photocatalytic tests demonstrate a strong influence of process conditions on the photocatalyst performance and on the reaction path. The packed-bed (PB) configuration reports a maximum “apparent quantum efficiency” of about 6.0% and a net thermal energy of 0.3 kW h/m2 generated in 120 h.

Optimization of heterogeneous photoelectrocatalysis on nanotubular TiO2 electrodes: Reactor configuration and kinetic modelling

Photoelectrocatalytic degradation of target molecules on nanotubular titanium dioxide (TiO2) immobilized on meshed conductive substrate was assessed by measuring the photoelectrochemical response (i.e., generated photocurrent) as indicator of TiO2 performance. Furthermore, a simple and reliable methodology for degradation modelling and laboratory reactor optimization has been proposed and validated. Nanotubular TiO2 was grown by anodic oxidation of Ti wire meshes and characterized by ESEM and XRD. Immobilized TiO2 on Ti wire mesh was used as photo-anode under UV irradiation (254 nm) and subjected to electrical polarization. The photocurrent was monitored in a three-electrode cell, by varying polarization voltage, TiO2 electrode relative positioning to the UV source (distance), and concentration of a model azo dye compound (Reactive Red 243, RR243). Photoelectrochemical response was modelled as a function of operating parameters and guidelines for photoreactor configuration were identified. Optimized batch photoreactor configuration (1.8 L) was used for degrading a 25 mg L−1 RR243 aqueous solution, achieving 90% decolorization in 45 min and 60% mineralization in 100 min. Decolorization kinetics were effectively described by means of a modified Langmuir-Hinshelwood model based on experimentally measured photocurrents, accounting for the dynamic behaviour of the process due to the change in solution transmittance over time determined by the degradation of target compounds.

Recent advances in photocatalysis for environmental applications

Advanced Oxidation technologies (AOTs) are gaining attention as an effective waste water treatment methodology capable of degrading diverse spectrum of recalcitrant organic contaminants and microbes. Undoubtedly, photocatalysis is a promising AOT to alleviate the problem of water pollution. Despite recent research into other photocatalysts (e.g. ZnO, ZnS, Semiconductor-Graphene composites, perovskites, MoS2, WO3 and Fe2O3), titanium dioxide (TiO2) remains the most popular photocatalyst due to its low cost, nontoxicity and high oxidising ability. Moreover, titania photocatalysts can easily be immobilized on various surfaces and be scaled up for large scale water treatment. The current review aims to highlight recent advancements in photocatalytic AOTs with main emphasis on TiO2 photocatalysis. This review also discusses the use of TiO2 photocatalysis for water and waste treatment, treating contaminants of emerging concern (CECs), pesticides, endocrine disrupters (EDs) and bacteria using both UV and visible light irradiations. It was concluded that with efficient photoreactor configuration and further studies on the photocatalyst regeneration, TiO2 photocatalysis is a viable option for the reclamation of agricultural/irrigational waste water. Novel doped photocatalysts such as ZnS-CuS-CdS, carbon spheres/CdS, g-C3N4-Au-CdS, ZnS-WS2-CdS, C3N4-CdS and Pd-Cr2O3-CdS have also been discussed. Finally, the advances in the actively studied metal organic framework based photocatalysts that are emerging as effective alternate for metal oxide based photocatalysts is also discussed in detail.

An innovative static mixer photoreactor: Proof of concept

An innovative application for the NETmix® reactor is validated in the present work, namely the homogeneous photo-Fenton treatment of natural waters contaminated with organic pollutants using solar light. Three antibiotics presenting high bacterial resistance (ciprofloxacin, sulfamethoxazole and trimethoprim) were selected as model pollutants. The influence of Reynolds number (Re=38–400) on the pollutants degradation was studied in continuous flow, and the flow rate and pH optimized (i.e., 500mLmin−1 and pH of 2.8, respectively). Under recirculation flow, the effect of different operating conditions on the degradation of the mixture of three antibiotics was then studied by changing the hydrogen peroxide (0–2.5mM) and iron (II) sulfate (0–4mgFeL−1) concentrations. Results establish high degradation rates using, 2.5mM H2O2, 2mgL−1Fe2+, pH of 2.8, 262Wm−2 irradiance and Re=300. Complete conversion of the antibiotics was achieved, demonstrating the potential application of the NETmix® technology as an efficient photoreactor configuration.

Supported Photocatalyst for Removal of Emerging Contaminants from Wastewater in a Continuous Packed-Bed Photoreactor Configuration

Water pollution from emerging contaminants (ECs) or emerging pollutants is an important environmental problem. Heterogeneous photocatalytic treatment, as advanced oxidation treatment of wastewater effluents, has been proposed to solve this problem. In this paper, a heterogeneous photocatalytic process was studied for emergent contaminants removal using paracetamol as a model contaminant molecule. TiO2 photocatalytic activity was evaluated using two photocatalytic reactor configurations: Photocatalyst solid suspension in wastewater in a stirred photoreactor and TiO2 supported on glass spheres (TGS) configuring a packed bed photoreactor. The surface morphology and texture of the TGS were monitored by scanning electron microscope (SEM). The influence of photocatalyst amount and wastewater pH were evaluated in the stirred photoreactor and the influence of wastewater flowrate was tested in the packed bed photoreactor, in order to obtain the optimal operation conditions. Moreover, results obtained were compared with those obtained from photolysis and adsorption studies, using the optimal operation conditions. Good photocatalytic activities have been observed and leads to the conclusion that the heterogeneous photocatalytic system in a packed bed is an effective method for removal of emerging pollutants.

Influence of the Photoreactor Configuration and of Different Light Sources in the Photocatalytic Treatment of Highly Polluted Wastewater

Abstract In this study, a highly polluted wastewater from tannery industry is treated by photocatalysis using home-made N-doped TiO2 as catalyst. The doping by nitrogen of titania particles leads to a reduction in the absorption threshold from 3.2 to 2.5 eV, permitting the absorption of radiation characterized by a wavelength in the visible spectrum.Experiments were carried out by using different light sources, in particular white LEDs, blue LEDs, and UV lamps, with the aim to evaluate the process efficiency at different operating conditions. The obtained performances were compared with those using an undoped commercial TiO2 catalyst (Degussa P25).Moreover, a simplified mathematical model capable to correlate the power input of the used light sources, the geometrical properties of the reactor, and emitting sources spectra with the performances of the photocatalytic reaction was developed.

Nano-ferrites for water splitting: unprecedented high photocatalytic hydrogen production under visible light

In the present investigation, hydrogen production via water splitting by nano-ferrites was studied using ethanol as the sacrificial donor and Pt as co-catalyst. Nano-ferrite is emerging as a promising photocatalyst with a hydrogen evolution rate of 8.275 μmol h(-1) and a hydrogen yield of 8275 μmol h(-1) g(-1) under visible light compared to 0.0046 μmol h(-1) for commercial iron oxide (tested under similar experimental conditions). Nano-ferrites were tested in three different photoreactor configurations. The rate of hydrogen evolution by nano-ferrite was significantly influenced by the photoreactor configuration. Altering the reactor configuration led to sevenfold (59.55 μmol h(-1)) increase in the hydrogen evolution rate. Nano-ferrites have shown remarkable stability in hydrogen production up to 30 h and the cumulative hydrogen evolution rate was observed to be 98.79 μmol h(-1). The hydrogen yield was seen to be influenced by several factors like photocatalyst dose, illumination intensity, irradiation time, sacrificial donor and presence of co-catalyst. These were then investigated in detail. It was evident from the experimental data that nano-ferrites under optimized reaction conditions and photoreactor configuration could lead to remarkable hydrogen evolution activity under visible light. Temperature had a significant role in enhancing the hydrogen yield.

A methodology for modeling photocatalytic reactors for indoor pollution control using previously estimated kinetic parameters

A methodology for modeling photocatalytic reactors for their application in indoor air pollution control is carried out. The methodology implies, firstly, the determination of intrinsic reaction kinetics for the removal of formaldehyde. This is achieved by means of a simple geometry, continuous reactor operating under kinetic control regime and steady state. The kinetic parameters were estimated from experimental data by means of a nonlinear optimization algorithm.The second step was the application of the obtained kinetic parameters to a very different photoreactor configuration. In this case, the reactor is a corrugated wall type using nanosize TiO2 as catalyst irradiated by UV lamps that provided a spatially uniform radiation field. The radiative transfer within the reactor was modeled through a superficial emission model for the lamps, the ray tracing method and the computation of view factors. The velocity and concentration fields were evaluated by means of a commercial CFD tool (Fluent 12) where the radiation model was introduced externally. The results of the model were compared experimentally in a corrugated wall, bench scale reactor constructed in the laboratory. The overall pollutant conversion showed good agreement between model predictions and experiments, with a root mean square error less than 4%.

CFD Analysis of the Radiation Distribution in a New Immobilized Catalyst Bubble Column Externally Illuminated Photoreactor

A new externally irradiated photoreactor configuration combining the excellent mass transfer characteristics of a bubble column operation with the separation power of an immobilized catalyst on quartz plates has been investigated using computational fluid dynamics (CFD) simulation. The radiative transport equation (RTE) in conjunction with the Navier-Stokes equations were solved to obtain the light incident radiative flux and the light absorbed by the immobilized titania as a function of the gas superficial velocity, the angle of inclination, and the separating distance between the plates. The model employed water and air as the fluid phases and the results indicated that gas bubbling considerably increased the incident radiation in the gas-liquid mixture enhancing the radiative flux and the absorbed radiation on the titania-coated plates. The CFD results pave the way for the optimization of a solar photocatalytic reactor for the degradation of organic pollutants.