Slurry Photocatalytic Reactor Research Articles

Enhancing a loosely coupled inductive wireless power transfer system for LED-driven slurry photocatalytic reactors

To improve the irradiation profile in a conventional photocatalytic reactor, an LED-based light emitter energized by the inductive power transmission (IPT) method has been proposed recently. However, technical challenges such as low coupling due to the asymmetrical wireless coupler, dynamic impedance due to multiple receivers and changing magnetic properties in the transmitter core, and ease in upscaling remain to be addressed. This work proposes an IPT system for an LED-based photocatalytic reactor using a toroidal transformer to match the impedance between a modified Helmholtz transmitter coil and a class-E inverter. A finite element magnetic field simulation and analytical calculation of the induced voltage are used to assess the field uniformity inside the coil. The mutual inductance at selected locations within the coil volume and the power transfer efficiency (PTE) are evaluated. The proposed system requires less than 2 W to generate a uniform magnetic field inside a 10.6 L acrylic cylinder with an induced voltage of 13.9 ± 0.95 Vrms along the cylinder’s central axis. The proposed wireless coupler achieves a coupling coefficient of 0.013–0.034 and a PTE of 23.7%, outperforming similar systems with asymmetrical coupler design while offering a versatile solution for integrating IPT technology into wastewater treatment.

Performance of a Solar-Driven Photocatalytic Membrane Reactor for Municipal Wastewater Treatment

The increasing demand for efficient wastewater treatment technologies, driven by global population growth and industrialisation, highlights the necessity for advanced, reliable solutions. This study investigated the efficacy of a slurry photocatalytic membrane reactor (PMR) for the advanced removal of organic pollutants, quantified via chemical oxygen demand (COD), under natural and simulated solar light irradiation. Employing two variants of iron-doped titania as photocatalysts and a polysulfone-based polymeric membrane for the separation process, the investigation showcased COD removal efficiencies ranging from 66–85% under simulated solar light to 52–81% under natural sunlight over a 7 h irradiation period. The overall PMR system demonstrated COD removal efficiencies of 84–95%. The results confirmed the enhanced photocatalytic activity afforded by iron doping and establish solar-powered slurry PMRs as an effective, low-energy, and environmentally friendly alternative for the advanced treatment of municipal wastewater, with the research providing valuable insights into sustainable water management practices.

Upgrade of a slurry photocatalytic membrane reactor based on a vertical filter and an external membrane and testing in the photodegradation of a model pollutant in water

Submerged slurry photocatalytic membrane reactors have been widely investigated in literature to combine photocatalysis and membrane separation in the mineralization of recalcitrant pollutants in wastewaters. However, submerged membranes are only able to retain the photocatalyst particles and not many types of pollutants. An upgraded configuration, based on a vertical filter (able to retain the photocatalyst) and an external nanofiltration (NF) membrane (able to retain pollutants in the photoreaction zone), has been designed, built and tested. To our knowledge, this novel configuration has never been proposed. The proof-of-concept on the working and behavior of the vertical filter in presence of the photocatalyst and the photocatalytic performance of the overall system, in a batch configuration, in the photodegradation of gemfibrozil as a model pollutant are reported. The filter was able to retain the TiO2 particles while ensuring greater flux compared to a submerged membrane (200 vs 40 L m-2 h-1 average values). The external membrane is not exposed to light irradiation, permits the recycle in the photoreactor of the non-photodegraded pollutants and produce a quality of the treated water (permeate) better than a submerged membrane. Some parameters (e.g.: TiO2 amount, pH, light intensity and wavelength, air and oxygen, membrane rejection) that influence the performance of this integrated system (photoreactor, filter and membrane) have been studied and discussed. Indeed, a pH 8.0 (giving 40–50 % rejection of the Fortilife NF membrane) was chosen against pH 9.7 (giving 90 % rejection), to avoid filter plugging. The obtained overall performance (80 % reduction of gemfibrozil concentration) can be further improved by a fine tuning of the various parameters.

Interaction forces and suspension characteristics in an oscillatory membrane photocatalytic reactor

The effects of the interaction between the hydrodynamic and colloidal forces on the suspension and performance characteristics of a slurry photocatalytic reactor equipped with oscillatory membrane and lateral turbulence promoters are investigated. Aggregation of catalyst particles is influenced by the magnitude of colloidal forces between the particles in relation to the hydrodynamic stresses acting on the aggregate. The interaction of the axial oscillatory shear with the transverse motion of the turbulence promoters (TP) results in generation of vortices and eddies that extended further away from the membrane surface leading to reducing particle aggregation. For the range of oscillatory conditions investigated, the aggregate size remained in the viscous subrange and decreased with increasing the oscillation intensity where an almost three folds decrease in aggregate size was achieved at high oscillation intensities. This resulted in reducing particles settling and deposition on the membrane surface which increased the catalyst specific area and volume fraction in suspension and enhanced both membrane flux and reaction rates. Improvement of the latter is also achieved by the microscale eddies attenuation of the concentration boundary layer surrounding the catalyst particles which results in better mass transfer. Using methylene blue dye (MB) degradation with ZnO photocatalyst under UV illumination as a model photocatalytic reaction, the investigation showed that increasing the oscillation intensity resulted in higher membrane flux and reaction rates that asymptotically approached maximum corresponding to near maximum catalyst suspension. This was estimated based on the magnitude of the eddy forces in the suspension in relation to the sedimentation and permeate drag forces acting on the catalyst particles. Comparison between the results of the present investigation and data from the literature showed satisfactory agreement.

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.

Techno‐Economic Evaluation of Photocatalytic H2S Splitting

This study presents a techno-economic assessment of a process involving conversion of H2S into hydrogen (a valuable clean fuel) and sulfur. A typical sour gas stream in the oil and gas industry was sweetened by scrubbing with aqueous solution of sodium hydroxide, and the dissolved H2S gas was converted using a TiO2 slurry photocatalytic reactor. More details can be found in article number 2100163, Giovanni Palmisano and co-workers.

An engineering approach towards the design of an innovative compact photo-reactor for antibiotic removal in the frame of laboratory and pilot-plant scale

Advanced Oxidation Processes (AOPs), in particular heterogeneous photocatalysis, have been considered as a promising method to remove antibiotics without generating hazardous intermediates. In this work, an innovative compact photoreactor was designed and tested for the degradation of the antibiotic Flumequine. The system consisted of a textile woven from both luminous and photocatalytically active fibers. The luminous fibers consisted of LED-type optical fibers and the photocatalytic fibers consist of textile fibers impregnated with TiO2. This configuration allowed for optimization of contact between the catalyst, the pollutant, and the light source. The surface morphology, elemental composition and optical properties of this photo-active fabric were characterized by SEM-EDX and by irradiance measurements. The effectiveness of the luminous textile was compared with two conventional processes: suspended TiO2, and immobilized TiO2 on cellulosic paper. The specific degradation rate obtained with the light textile was 28 times higher than that observed with slurry photocatalytic reactor and 65 times higher than in the case of TiO2 supported on cellulosic paper. Luminous textile also showed efficient performance in terms of mineralization per Watt consumed with values exceeding 77 and 419 times than those obtained with suspended TiO2 and the cellulose paper, respectively. This new configuration also improved the compactness by 3 times compared to the cellulosic paper system. The Langmuir-Hinshelwood model showed that this optical fibers-based configuration reduced the mass transfer compared to the conventional TiO2 immobilization approaches. Additionally, the extrapolation of this process to pilot scale was successfully performed. The excellent performances in terms of degradation rate, mineralization per Watt consumed, compactness, energy consumption, and reusability make luminous textiles an attractive alternative to conventional photocatalytic reactors’ design for removal of antibiotics in water and wastewater.

Synergic effects on degradation of a mixture of polycyclic aromatic hydrocarbons in a UV slurry photocatalytic membrane reactor and its cost estimation

In this study, batch experiments were conducted to investigate the removals of three polycyclic aromatic hydrocarbons (PAHs) namely phenanthrene (PHE), naphthalene (NAP) and acenaphthene (ANA) as a mixture during photocatalysis (UV-TiO2), membrane separation (MS) and integrated photocatalytic membrane (UV-TiO2 + MS) processes in an indigenously developed integrated photocatalytic membrane reactor (PMR). Synergic effects were observed during the removals of model compounds when they were in the mixture as compared to their removals as a sole compound in aqueous solutions. The mineralization efficiencies in terms of total organic carbon (TOC) removals were also evaluated during UV-TiO2 and UV-TiO2 + MS processes. The degradation of PAHs mixture during photocatalytic degradation followed the pseudo-first order kinetics. Furthermore in this study, the cost estimation of PMR was carried out by calculating the treatment cost for both advanced oxidation process (AOP) system and membrane (MS) process separately. The treatment cost per m3 of effluent containing PAHs in PMR was found to be $ 10.4 to $ 13.6 or ₹ 728 to ₹ 752.

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.

Feasibility study of acenaphthene degradation in a novel slurry UV photocatalytic membrane reactor: Effect of operating parameters and optimization using response surface modeling

The study focusses on the removal of acenaphthene (ANA) in an indigenously developed UV-TiO2 slurry photocatalytic membrane reactor (PMR). The various operating variables such as pH (3.0–9.0), TiO2 dosage (0.1-0.9 g/L) and initial ANA concentration (1000−3000 μg/L) on removals of ANA and total organic carbon (TOC) were investigated. The experimental results of the integrated photocatalytic membrane process (UV-TiO2 + MS) during the batch study showed ANA and TOC removals of 95.3% and 93.8 % and 93.8 % respectively while the individual processes; photocatalytic process (UV-TiO2) (ANA-80.1 % and TOC-57.6 %) and UF membrane separation (MS) (ANA-51.1 %) exhibited low removal rates with the same experimental conditions. The photocatalytic degradation of ANA followed pseudo-first-order kinetics and the obtained experimental data were analyzed with Response Surface Methodology (RSM) using Design-Expert software. This study also identified the various intermediates that were generated during the photocatalytic membrane treatment of ANA. The ANA and TOC removals were also monitored during continuous process and the highest ANA and TOC removals of 95.1 % and 93.2 % respectively were noticed after 560 min of the reactor run during UV- TiO2 + MS process. Similarly, the highest removals of 80 % ANA and 57.3 % TOC were observed during UV-TiO2 process on the continuous mode of experiments.

Investigation of Naphthalene Removal from Aqueous Solutions in an Integrated Slurry Photocatalytic Membrane Reactor: Effect of Operating Parameters, Identification of Intermediates, and Response Surface Approach

A laboratory scale indigenous integrated slurry photocatalytic membrane reactor (PMR), coupling TiO2/UV-C photocatalysis and ultrafiltration (UF) membrane process was evaluated for the removal of naphthalene (NAP)—one of the low molecular weight polycyclic aromatic hydrocarbons (PAHs), frequently detected in municipal and industrial wastewaters. The different operational parameters such as initial NAP concentration (5–25 mg/L), catalyst dosage (0.1–0.9 g/L), and feed solution pH (3–9) were investigated for NAP and total organic carbon (TOC) removal. The experimental results obtained from the batch study of the integrated process showed 92.8% and 90.2% of NAP and TOC removals while the individual processes; UV-TiO2 (76.8% NAP and 56.4% TOC removals) and UF membrane separation process (49.1% NAP removal) exhibited low removal rates for the same experimental conditions. The NAP and TOC removals obtained during continuous flow studies were 93.1% and 91.4% at 180 min and thereafter remained constant up to 560 min of reactor running time. This study also includes the identification of intermediates that are formed after 30 min of operation of PMR. The photocatalytic degradation of NAP followed pseudo-first-order kinetics and the obtained experimental data were analyzed with response surface methodology (RSM) using design expert software.

Investigation of phenanthrene degradation in a slurry photocatalytic membrane reactor: Influence of operating variables and data validation

Investigation of phenanthrene degradation in a slurry photocatalytic membrane reactor: Influence of operating variables and data validation

Photocatalytic Degradation of Aqueous Phenanthrene in a Slurry Photocatalytic Reactor:Optimization and Modelling

Photocatalytic Degradation of Aqueous Phenanthrene in a Slurry Photocatalytic Reactor:Optimization and Modelling

Performance of an indigenous integrated slurry photocatalytic membrane reactor (PMR) on the removal of aqueous phenanthrene (PHE).

In this study, a slurry photocatalytic membrane reactor (PMR) was developed and evaluated for the degradation of aqueous phenanthrene (PHE). During continuous process with a hydraulic retention time (HRT) of 140 min, the maximum PHE degradation and total organic carbon (TOC) removal efficiencies were found to be 97% and 79%, respectively. The reuse and recovery potential of TiO2 was studied with continuous recycling. The major intermediates during photodegradation of PHE were found to be phenanthrenequinone, phenanthenol and fluorine. This study also includes an investigation of membrane fouling caused by hydrophilic nano TiO2. The cake layer observed on the membrane surface was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive spectroscopy (EDS). In addition, the effect of operating parameters such as pH and permeate flux on membrane fouling were also investigated. Low permeate flux and alkaline conditions reduced membrane fouling.

Degradation Efficiency of Textile and Wood Processing Industry Wastewater by Photocatalytic Process Using In Situ Ultrafiltration Membrane

The hybrid membrane photocatalytic reactor (MPR) in this study was constructed by submerging a flat polyethersulfone membrane module into a ZnO or TiO2 slurry photocatalytic reactor for raw wastewater treatment. The short and long term MPR performance was investigated for the degradation of textile and wood processing industry wastewater. The different operational parameters such as the catalyst type, catalyst loading, initial wastewater concentration, light type, and semiconductor powder type affecting the performance of the reactor were initially evaluated using a batch system without a membrane module. After the optimization of the operating conditions, the long term studies were performed by the MPR. Nearly 100% color and 30–55% chemical oxygen demand (COD) removal could be reached at a hydraulic retention time of 6 h for both wastewater effluents. Moreover, reverse osmosis experiments were applied on MPR ultrafiltration effluent for further COD removal and up to 88% COD removal efficiency could be obtained. The color and organic matter degradation efficiency showed that the catalyst can be reused effectively in MPR. In this hybrid design, the membrane module served also as a separator which is very advantageous in keeping catalyst powder in suspension during the operation. The results indicated that the effluent water can be used as process water in the industry.

Study on particle and photonic flux distributions in a magnetically stirred photocatalytic reactor

When dispersed in water, nanoscale photocatalysts can aggregate into microscale secondary particles due to their high surface energy. The interaction between the incident photons and the aggregated particles is expected to be significantly changed due to their comparable length scales. Hydrodynamics of the particles after aggregation and the resultant photonic flux distributions in slurry photocatalytic reactors are therefore essential. The magnetically stirred photocatalytic reactor is compact and simple for fabrication, and therefore can be readily employed in lab-scale photocatalytic tests. However, studies toward its optimization are rare. In our study, the photocatalyst distribution was simulated using a Eulerian–Lagrangian approach, while the evolution of free liquid surface led by magnetic stirring was modeled by volume of fluid method. Subsequently, based on the photocatalyst distribution, the photonic flux distribution was obtained through a mean free path-based Monte Carlo method. Outcomes suggest that at a stirring speed of 900 rpm, the 10 μm particles can be well suspended, and a moderate free liquid surface will also be present. Moreover, under sufficient stirring, larger catalyst particles are more likely to be densely distributed in the outer region, which contributes to an increase in the overall photonic absorption even higher than the one with evenly distributed photocatalysts.

CFD simulation of a pilot scale slurry photocatalytic reactor and design of multiple-lamp reactors

The hydrodynamics behaviour and radiation transport occurring inside a pilot-scale slurry photocatalytic reactor (treating real shower water) with large diameter was investigated using computational fluid dynamics (CFD). The multiphase flow system was solved using a granular Eulerian model while the solution of the radiative transport equation (RTE) was solved using the finite volume based discrete ordinate model (DOM). Multiphase simulation showed recirculation zones caused by the high slurry inlet velocity. Due to the rapid attenuation of light occurring radially within the reactor, regions of varying reaction orders exist, i.e., half order reaction close to the lamp and first order reaction further from the lamp, as the incident radiation goes below a certain value. A rate equation relating pollutant degradation to the rate occurring in the half and first order reaction regions (in terms of local volumetric rate of energy absorption – LVREA) was proposed. Using a value of 225Wm−2 as the minimum incident light intensity at which half order reactions take place, a Pearson correlation of 0.88 between simulated and experimental data indicated that the proposed model satisfactorily described the experimental observations. Next, simulations performed with a system of multiple lamps (2 and 4 lamps) at different geometrical arrangements (i.e. with the lamps separated by the distance Xlamp) showed that within the range of catalyst concentration investigated, the maximum potential increases in reaction rate was 56% and 123% when using 2 and 4 lamps (at optimum lamp arrangement) respectively, as compared to using one lamp. The increase in reaction rate occurred due to the maximisation of incident radiation contours at which first order reactions take place. The optimum lamp separation was dependent on the catalyst concentration in the wastewater and decreased with increasing catalyst concentration.

Lamp emission and quartz sleeve modelling in slurry photocatalytic reactors

Modelling of incident radiation intensity in a reaction medium or at catalyst surface is a necessity for kinetics modelling of pollutant degradation in photocatalytic reactors. In slurry photoreactors, the incident radiation within the reacting medium is calculated via the radiative transport equation (RTE) which considers the absorption and scattering of light due to the catalyst particles. As a result, a proper lamp emission model is required so as to obtain boundary conditions of the incident radiation entering the reacting medium. In this paper, we examine the validity of line, surface and volumetric source models at describing the incident radiation around a UV lamp. We then examine the effects of different lamp length to lamp radius ratios (2L/rlamp) and lamp ageing on the lamp emission model, with respect to the more descriptive and accurate volume source model. Finally, computational fluid dynamics (CFD) simulations are performed to determine the effect of light reflection, refraction and absorption at the air–quartz–water interfaces on incident radiation entering the reaction medium, for three quartz tube radius to lamp radius ratios (rquartz/rlamp) and two typical quartz tube thicknesses. The results obtained in this study are conveniently presented in dimensionless form and could be used as correction factors in the setting up of the radiation boundary condition in the modelling of cylindrical slurry photocatalytic reactors.

Degradation of Thiacloprid by ZnO in a Laminar Falling Film Slurry Photocatalytic Reactor

The possibility of the use of the laminar falling film slurry type photoreactor was examined in conjunction with ZnO as a photocatalyst for the removal of thiacloprid (TCL) from Calypso 480–SC commercial formulation by UV radiation. The degradation kinetics were monitored by HPLC–DAD, while the disappearance of the nitrile group, i.e. TCL and intermediates containing this group, was followed by FTIR. The study of TCL removal under different operating conditions indicated that 2 g/L of ZnO was an optimal catalyst loading, and the optimal pH was 6.8. In the investigated range of initial concentrations of TCL (0.05–0.38 mM), the photocatalytic degradation in the first stage of the reaction followed approximately a pseudo-first-order kinetics. The increase of UV-light intensity resulted in a linear increase in the rate of TCL degradation. The figure-of-merit electrical energy per order was employed to estimate the electrical energy consumption. Because the efficiency of TCL photodegradation in the natural thermal water was about two times lower than in distilled water, the investigation encompassed the influence of the thermal water components, i.e. different inorganic ions and humic acid, on the rate of TCL degradation.

Bubbles scatter light, yet that does not hurt the performance of bubbly slurry photocatalytic reactors

This paper provides a simple guideline to quantify at what gas fraction and bubble diameter bubbles start having a considerable effect on the performance of a bubbly slurry photocatalytic reactor. The local rate of photon absorption, responsible for local photoreaction rate, is affected in the presence of bubbles, as bubbles scatter the photons in all directions. Here, we consider a simple 1D description of a photoreactor, and implement a bidirectional scattering model for photocatalytic particles and bubbles to set up photon balances in the photoreactor. Both low and high light intensities are considered, with a linear and square root dependence of reaction rate on the local volumetric rate of photon absorption, respectively. The photon balances, coupled with component balances, lead to a closed-form expression for the critical gas fraction that causes a 5% deviation in the photoreaction rate, when compared to an ungassed reactor with the same amount of catalyst per unit reactor volume. We further show that in typical bubbly slurry photoreactors, with gas fractions smaller than 20% and bubble sizes of about 3mm, the effect of bubbles on the rate of photon absorption and photoreaction is negligible. Moreover, the overall efficiencies are calculated at different gas fractions and bubble diameters. Other operational aspects of three-phase photoreactors are calculated and briefly discussed. The general conclusion is that the distribution of light inside a photoreactor is hardly affected by the presence of bubbles.