Thin-film Reactor Research Articles

Importance of organic- and inorganic-based electro-precipitation on the advanced electro-oxidation efficiency towards reclaimed wastewater treatment in thin-film reactor – Mechanistic and modeling studies

To face the global water crisis with the increase of both water demand and water stress, it is necessary to consider wastewater effluent as a non-conventional water resource. However, before reusing this water, it is compulsory to apply complementary treatment to it so that the water discharge will be in full agreement with the regulations befitting the water reuse purpose. Electrochemical systems have been demonstrated to offer good performance in removing recalcitrant pollutants, but the influence of the matrix of reclaimed wastewater, and particularly the phenomenon of cathodic electro-precipitation has barely been considered until now. Therefore, a detailed mechanistic and modeling study of the influence of cathodic organic- and inorganic-based electro-precipitation on the advanced electro-oxidation efficiency for reclaimed wastewater treatment is newly proposed. For the first time, the predictive model takes into account multi-phenomena such as local cathodic alkalization, cathodic electro-precipitation of CaCO3, Ca3(PO4)2, as well as organic co-precipitation, anodic oxidation of carbonates, and electro-oxidation of organic contents. The results demonstrated that electro-precipitation increased with the use of real reclaimed wastewater compared to the simulated wastewater due to the co-precipitation of organics. Higher current density (16 mA cm−2) led to the anodic oxidation of carbonates, which reduced their ability to be precipitated on the cathode. Tylosin, a representative micropollutant, could be fully degraded using the stipulated thin-film electrochemical reactor. However, chlorinated and nitrogenous by-products accumulated at such a range of currents, and hypochlorous acid occupied a central role in the overall oxidation pathways that have been proposed.

Thin-film fixed-bed reactor for photocatalytic degradation of synthetic food dye Sunset Yellow from contaminated waters and optimisation of process by response surface method

ABSTRACT In recent years, the advanced oxidation processes have been used to treat wastewater containing various dye pollutants through various methods of purification. In this study, the removal of the Sunset Yellow (SY) dye from contaminated water was investigated by UV/TiO2/H2O2 process using a recirculating thin-film fixed-bed reactor (TFFBR). The experiments were designed by the response surface method (RSM) via Minitab software, in such a way that the effects of various parameters on the process are investigated. The effect of different parameters such as reaction time, pH of the solution, initial dye concentration and hydrogen peroxide concentration on the dye removal efficiency has been investigated. According to the results of the screening and optimisation test by the response surface method, the optimal conditions for performing the process were, time of 45 min, pH of 2, hydrogen peroxide concentration of 13.33 mM and initial dye concentration of 10 mg/L. Under optimal conditions, the efficiency of dye removal was more than 97%. Besides, the kinetics of SY dye removal followed the first-order equation.

Continuous-flow synthesis of ultrahigh luminescent perovskite nanocrystals using forced thin film reactor and application for light-emitting diodes

Owing to their excellent optical properties, organolead halide perovskite nanocrystals (PeNCs) have gained significant attention. Considering their industrial contribution, exploring practical production of high-quality PeNCs is of major importance. In this work, we demonstrate continuous-flow synthesis of ultrahigh luminescent PeNCs with high color purity using a forced thin film reactor. We successfully demonstrate the effectiveness of this reactor as a crystal growth environment. The photoluminescence quantum yields were improved to 94% as a result of the unique mixing process. After film formation, this reactor enabled the application for perovskite light-emitting diodes.

Inactivation of E. coli and L. innocua in milk by a thin film UV-C reactor modified with flow guiding elements (FGE)

In this study the suitability of a thin-film reactor (TFR) equipped with special flow guiding elements (FGE) was examined to analyse its capability to inactivate microorganisms in milk. Experiments were carried out with UHT-milk inoculated with Escherichia coli (E. coli), DH5α and Listeria innocua (L. innocua) WS 2258. Furthermore, the inactivation of microorganisms originally occurring in raw milk was investigated. E. coli, DH5α and L. innocua serving as biodosimeter were reduced by 4.58-log and 3.19-log, respectively. In milk, the original microorganisms showed a 4-log reduction. Without FGE the reduction was below 0.13-log. Thus, it can be derived that the efficacy of a UV-C thin-film reactor processing absorptive media like milk can be highly improved using FGE.

Unprecedented reactive electro-mixing reactor: Towards synergy between micro- and macro-reactors?

Over the last century, electrochemistry has contributed to societal progress through the development of electrochemical industrial processes. Since the first battery was proposed by Alessandro Volta in 1799, the vision of the electrochemical cell has not changed significantly: static electrodes (or semi-static in rotating disk and cylinder systems) are immersed in an electrolyte while the solution is either stirred for better homogenization or pumped between or through the electrodes. This work intends to induce a paradigm shift in the design of electrochemical cells that could have tremendous positive impacts on the mechanisms (e.g. transfers), the process efficiency and the scalability of electrochemical processes. It is proposed to set whole thin film electrochemical cells in motion within a stirred tank macro-reactor, with the aim of synergistically combining the properties characteristic of the micro-scale in thin film reactors with those of the macro-reactor.This paper highlights the superiority of the unprecedented “reactive electro-mixing” reactor in water treatment, i.e. 1.32 times higher degradation efficiency and 20 times lower energy requirement than a conventional filter-press cell. It further announces the birth of a new “reactive electro-mixing” sub-discipline that should lead to many other scientific studies and industrial applications.

Synthesis of highly luminescent CH3NH3PbBr3 perovskite nanocrystals via a forced thin film reactor

Highly luminescent CH3NH3PbBr3 perovskite nanocrystals (PeNCs) with a high photoluminescence quantum yield value of 80% are prepared by a forced thin film reactor for continuous production. In this system, the rotating and stationary disks form a confined micro space which demonstrates a unique mixing process through continuous injection of solvents. We found that the unique mixing system leads to colloidal PeNCs with 4 nm–10 nm, which are much smaller than those of a representative T-junction system (15 nm–65 nm). It suggests that a confined micro space is effective for the capping of n-octylamine to the surface of PeNCs, resulting in suppression of the aggregation of the PeNCs and crystal growth. Also, with increasing flow velocity, the optical properties show almost no fluctuation. This system is a promising continuous system to prepare colloidal PeNCs, and can provide a synthetic protocol to be applied for light-emitting diodes as well as various other optoelectronic devices.

Application of a Microreactor to Pharmaceutical Manufacturing: Preparation of Amorphous Curcumin Nanoparticles and Controlling the Crystallinity of Curcumin Nanoparticles by Ultrasonic Treatment

Amorphous nanoparticles of curcumin (ANC) with primary particle sizes of 50 to 100nm were prepared using a forced thin film reactor (FTFR). An ethanolic solution of curcumin and polyvinylpyrrolidone was mixed with purified water in an FTFR to precipitate the curcumin nanoparticles. In order to obtain amorphous particles, the solvent used and the operation conditions of FTFR such as the rotation speed of the disk and the flow rate of solutions were adjusted. According to powder X-ray diffraction (XRD) analysis and Fourier transform infrared spectroscopy (FT-IR), amorphous curcumin nanoparticles were obtained. To control the crystallinity, ultrasonic treatment was carried out on ANC suspended in water or hexane to which a polymer or a surfactant was added to prevent the growth of the particles. Transmission electron microscopy, XRD, and FT-IR analyses indicated that the treatment enabled the transformation of ANC to crystalline form 1 (a fundamental curcumin structure) and then to crystalline form 2 or crystalline form 3 without any change in the size of the primary particles. These findings suggest the possibility of preparing solid particles with a desired particle size and crystallinity.

Variations in sludge organic composition and dewatering behaviors through visible light driven photocatalysis: In-situ O2 generation

In this research, carbon and nitrogen doped TiO2 nano-particles were successfully synthesized and immobilized onto inner surface of a tubular thin film reactor (TTFR). CO3-NxOy-TiO2 nano-composite thin films (NCTF(s)) were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Characterization results indicated that the CO3-NxOy-TiO2 NCTF has a broad adsorption edge in the visible light region. Decorated TTFR was used to observe the impacts of visible light irradiation on sludge dewatering characteristics and organic structure. In the experiments, H2O2, NaOCl and their various gravimetric combinations were added to the sludge as electron acceptor combination (EAC). Obtained experimental results revealed a photocatalytic synergy between hydrogen peroxide and chlorite molecules. The optimum H2O2 and OCl mixing dosage for photocatalytic and photolytic experiments was determined to be 0.02 g H2O2 g−1 DS and 4 × 10-3 g−1 NaOCl g−1 DS, respectively. The pseudo-first order kinetic constants (kobs) for volatile solids (VS) removal observed in EAC3 (with NCTF), EAC2 (with NCTF) and photolysis were 0.140 min−1, 0.045 min−1 and 0.025 min−1, respectively. The average VS removal rate depending on the applied unit photonic power to unit TTFR area was 218 ± 14 mgVSremoved W−1 h−1 cm−2. Experimental results obtained using different EAC(s) dosage schemes revealed that O2 was the main active specie and HO radicals also contributed to sludge treatment. Naphthalene, pyrene, anthracene and phenanthrene were detected in raw sludge and removed 87 ± 1% by the method.

A comparison between the four Geldart groups on the performance of a gas-phase annular fluidized bed photoreactor for volatile organic compound oxidation.

Heterogeneous photocatalytic oxidation (PCO) is a widely studied alternative for the elimination of volatile organic compounds (VOC) in air. In this context, research on novel photoreactor arrangements to enhance PCO rates is desired. Annular fluidized bed photoreactors (AFBPR) have yielded prominent results when compared to conventional thin film reactors. However, very few works aimed at optimizing AFBPR operation. In this study, TiO2 photocalytic agglomerates were synthesized and segregated in specific size distributions to behave as Geldart groups A, B, C, and D fluidization. The TiO2 agglomerates were characterized by XRD, FTIR spectra, and N2 adsorption. Photocatalyst performances were compared in a 10-mm gapped AFBPR for degrading the model pollutant methyl-ethyl-ketone (MEK), using a 254-nm radiation source. Geldart group C showed to be inadequate for AFBPR operation due to the short operation range between fluidization and elutriation. In all the cases, photocatalytic reaction rates were superior to sole UV photolysis. Group A and group B demonstrated the highest reaction rates. Considerations based on mass transfer suggested that the reasons were enhanced UV distribution within the bed at lower flow rates and superior catalyst surface area at higher flow rates. Results also revealed that groups A, B, and D perform equally per catalyst area within an AFBPR if the fluidization numbers (FN) are high enough.

High yield accelerated reactions in nonvolatile microthin films: chemical derivatization for analysis of single-cell intracellular fluid.

The identification of trace components from biological media can require derivatization under mild conditions for successful analysis by mass spectrometry (MS). When aqueous droplets (ca. 500 nL) containing a sugar and an amine as reagents are allowed to evaporate they may form long-lasting microthin films in which derivatization reactions can occur fast relative to reaction rates in bulk solution. Evidence is presented that these reactions are heterogeneous in nature and comparisons are made with reactions in pastes and in neat reagent mixtures. Moreover, these thin film reactors can be made stable for the long periods of time that may be necessary to give high product yields. The situation is typified by imine formation from reducing sugars which have reaction times of much more than 1 hour provided that small concentrations (e.g. 20 ppm) of nonvolatile solvents are included. After evaporation of almost all the water, the reaction occurs at an approximately constant rate for the first hour. The rate is two orders of magnitude faster than the reaction in the corresponding homogeneous saturated bulk solution. Conversion of the reagent to the Schiff base product is 67% to 96% efficient in these long-lasting thin films, in sharp contrast to the corresponding derivatization efficiencies in the bulk of less than 1%. This method was used to chemically derivatize and thus to identify, using tandem mass spectrometry, 29 reducing sugars in ca. 1 nL of intracellular fluid from a single onion epidermis cell. A formal description of the kinetics of reversible and irreversible second order reactions in thin films is provided. The effects of thermodynamic and kinetic factors are separated and the measured apparent acceleration factor is shown to represent the ratio of intrinsic rate constants for the microthin film reactor relative to the bulk reaction.

Experimental and Numerical Study of the Hydrodynamics of a Thin Film Reactor (TFR) for the Decarboxylation of Anacardic Acid

Abstract A newly designed laboratory scale thin film reactor (TFR) was tested for the decarboxylation of anacardic acid in Cashew Nut Shell Liquid (CNSL) and to investigate the fluid flow behaviour under the influence of temperature since the fluid properties like viscosity and density have strong dependence on temperature. The CNSL containing 60–65 % anacardic acid was decarboxylated to produce cardanol and CO2 at wall temperatures ranging between 393 K and 433 K, respectively. The characteristics of the CNSL, essentially a non-Newtonian fluid, was analysed at different temperatures and its rheological behaviour was studied using the well-known power law model. It was observed that CNSL follows a pseudoplastic behaviour and its viscosity, along with the liquid residence time, was found to decrease till 413 K, while a further increase in temperature resulted in product degradation due to charring, accompanied by an increase in viscosity and residence time. Using measured values for the viscosity, the film thickness was calculated for each wall temperature within the 393–433 K temperature range, showing an increase of the film thickness with temperature and viscosity. Computational Fluid Dynamics (CFD) studies were carried out for the first time for this reactor configuration, using the volume of fluid (VOF) model for the reactive flow. The results obtained from these simulations were in concurrence with the experimental outcomes: velocity profiles along the length of the reactor show its highest values at a wall temperature of 413 K, while lower velocity values were observed when the temperatures were lower or greater than 413 K.

Experimental study of the effects of showerhead configuration on large-area silicon-nitride thin film by plasma-enhanced chemical vapor deposition

Showerhead is a typical and important part in a vertical plasma-enhanced chemical vapor deposition (PECVD) reactor. A contrast experiment with the same recipe but different showerhead configurations was carried out, where the effects of the blocked area, position and drilling depth of the arrayed holes on the full-wafer deposition rate and the ratio of nitrogen to silicon of the silicon-nitride thin film were examined. The results of the blocking-hole scheme demonstrate that: the deposition rate is higher under the blocked region; the gradients of the deposition rate in the edge-opened configurations are larger than those in the center-opened configurations; the tendency of the ratio of nitrogen to silicon goes up towards to the centroid in the edge-opened configurations. The results of the drilling-hole scheme show a similar characteristic, however, the gradients are much smoother than those in the blocking-hole scheme. These results indicate that it is a feasible way to globally or locally refine the qualities of the large-area thin film through tailoring or varying the drilling depth of the arrayed holes on the showerhead face plate. This paper contributes to the structural design for the large-area silicon-nitride thin-film PECVD rector with vertical showerhead, and can also be referred to the other large-area thin-film reactor with multi-hole arrayed showerhead.

Effect of copper on the growth and photochemical properties of lanthanum manganite film electrode

This study demonstrates that p-type copper-doped lanthanum manganite (LaMnO3) film on aluminum plate substrate is a stable and efficient photo-absorber for hydrogen collection from water. Compared to using photocatalyst powder, thin-film reactor is a convenient method for industrial applications as no further filtration process is required. The copper-doped LaMnO3 semiconductor films were readily deposited on aluminum plate substrates via sol-gel approach as well as spin-coating technology using photoelectrochemical cathodic current under AM 1.5G illumination (100mW/cm2). The influences of copper loading on LaMnO3 films in terms of surface and internal pore structure, morphology, optical and photoelectrochemical properties were comprehensively investigated. The bandgap energy and carrier density of the copper-doped LaMnO3 films were found to range between 2.670–2.677eV and 4.80×1015–6.18×1015cm−3, respectively. The flat band potentials of these films lied in the range of −0.424 to +0.067V vs. Ag/AgCl electrode (or −0.217 to +0.232V vs. NHE) based on the Mott-Schottky measurements. When the molar ratio of copper in the reaction solution was higher than 0.6, the copper-doped LaMnO3 film possessed the characteristics of a p-type semiconductor and yielded the best photo-performance when compared to n-type semiconductor films.

Plasmonic photocatalytic reactor design: Use of multilayered films for improved organic degradation rates in a recirculating flow reactor

Plasmonic photocatalysis was investigated by examining both the arrangement of the photocatalyst and plasmonic components, and the structure and composition of the plasmonic phase. Pd was epitaxially grown on to 50nm Ag nanocubes. The Ag:Pd ratio was optimized to blue-shift the plasmonic absorption peak to match the bandgap of TiO2 (∼405nm). A∼5nm Pd coating on the Ag nanocubes (Ag:Pd=9:1) led to the observation of the Ag nanocube’s plasmonic feature. The arrangement of the photocatalyst components was tested for degradation of model organics in a slurry and a recirculating thin film photoreactor. The results demonstrated that both the arrangement of the components and the structure and composition of the plasmonic material influenced the conversion. The TiO2/Ag composite catalysts yielded slight improvement (in thin film reactor) or had a negative effect (slurry reactor) compared to TiO2 which was attributed to scattering light away from the semiconductor photocatalyst and/or covering some active sites. The addition of the Pd shell on the Ag nanocube yielded improved performance compared to the TiO2/Ag composite catalysts, likely due to electron trapping. A factor of 2 enhancement in rate and apparent quantum yield compared to TiO2 was achieved for the Ag NC layer underneath the TiO2 layer and was attributed to light scattering of absorbed photons. The addition of the Pd shell to the Ag nanocube still provided enhancement compared to TiO2, but was lesser compared to Ag layer due to lower scattering efficiency. The results of this study provide insights for plasmonic photocatalytic reactor design. Best utilization of plasmonic enhancement to photocatalysis is indicated via a layered design of the plasmonic and photocatalytic phases.

Sono-photo-degradation of carbamazepine in a thin falling film reactor: Operation costs in pilot plant

The photo-Fenton degradation of carbamazepine (CBZ) assisted with ultrasound radiation (US/UV/H2O2/Fe) was tested in a lab thin film reactor allowing high TOC removals (89% in 35min). The synergism between the UV process and the sonolytic one was quantified as 55.2%.To test the applicability of this reactor for industrial purposes, the sono-photo-degradation of CBZ was also tested in a thin film pilot plant reactor and compared with a 28L UV-C conventional pilot plant and with a solar Collector Parabolic Compound (CPC). At a pilot plant scale, a US/UV/H2O2/Fe process reaching 60% of mineralization would cost 2.1 and 3.8€/m3 for the conventional and thin film plant respectively. The use of ultrasound (US) produces an extra generation of hydroxyl radicals, thus increasing the mineralization rate.In the solar process, electric consumption accounts for a maximum of 33% of total costs. Thus, for a TOC removal of 80%, the cost of this treatment is about 1.36€/m3. However, the efficiency of the solar installation decreases in cloudy days and cannot be used during night, so that a limited flow rate can be treated.

Determination of optimum extinction wavelength for paracetamol removal through energy efficient thin film reactor

Abstract Paracetamol (PAM) mineralization through nano-composite thin film (TF) based photocatalytic system was investigated under variable operational conditions. The experiments were conducted using a non-stirred flow through coated tubular quartz reactor (TQR). Elimination of energy demand arising from stirring and aeration through the developed TF reactor configuration was also among the main research interests. Ag-doped Si-TiO 2 TFs were grown on Si-decorated inner surface of the TQR using sol-gel dip coating technique. The fabricated TF was characterized by SEM-EDS, TEM, AFM, XPS and UV vis spectroscopy methods. TF-based PAM mineralization kinetics were observed for both UV vis and UV wavelengths using pure, Si-Ti and Ag-doped Si-TiO 2 TF(s). The direct and indirect optical ban gap energies (BGE) for the Ag doped Si-TiO 2 TF were estimated to be 2.56 eV and 2.86 eV respectively. While no visible light activity was observed for pure TiO 2 TF, Ag-doped Si-TiO 2 TF exhibited significant PAM degradation activity for λ > 400 nm with a k obs value of 2.1 ± 0.1 10 −3 min −1 . In addition to known phenolic and carboxylated intermediates, UV vis spectroscopy, HPLC–MS and UPLC–MS/MS measurements indicated α-cyano-4-hydroxicinnamic acid (αPHC) formation as a result of photo-addition reactions under UV C irradiation. Experimental results also indicated that αPHC blocks h + /e − formation completely. Paracetamol could be degraded economically under UV B irradiation through the fabricated TF reactor without stirring, aeration or adding external electron acceptors.

English

Activated Carbon prepared from Sugarcane Bagasse(SC) was selected as the suitable adsorbent for CO2 sequestration and an experimental analysis was carried out to study the effectiveness of adsorption of the vehicular exhaust on the adsorbent. The adsorbent was prepared by slow pyrolysis of Sugarcane Bagasse at 600oC. Because of the increasing level of greenhouse gases in the atmosphere due to our dependence on fossil fuels, the need to create a cost efficient,reusable material with a high CO2 adsorption capacityhas become necessity. In this paper the FTIR analysis of the SC600oC was carried out. The vehicular exhaust was injected into a thin film reactor after H2S removal. The effectiveness of adsorption was tested at an emission testing centre while removal of H2S was tested by simple qualitative analysis.

CFD Simulation of UV Disinfection Reactor for Applesauce with a Low UV Absorption Coefficient

In this study, a Computational Fluid Dynamics (CFD) model was developed to evaluate ultraviolet disinfection applesauce reactor. To simulate UV reactors, three sets of equations, including hydrodynamics, radiation and species mass conservation were solved simultaneously. The Realizable k-e turbulence model and the discrete ordinate method were used to find the UV radiation profile through the reactor. Using the Chick-Watson kinetic model and the Eulerian framework, inactivation of applesauce microorganisms was simulated in the UV reactor. Simulation results for water disinfection in the UV reactor were evaluated by the reported experimental data. Simulation was extended for non-Newtonian fluid such as applesauce. Results show that the UV reactor is less effective in eliminating microorganisms from applesauce than from water because applesauce has a higher UV absorption rate. In order to achieve higher disinfection of the UV reactor for non-Newtonian fluids with high absorption, this study examined different parameters and makes suggestions for appropriate reactor design. Different designs for disinfection reactor were studied, due to higher UV absorption coefficient of applesauce, CFD simulations show that the inactivation of microorganisms in applesauce is less than water, consequently thin film or small radius reactors are appropriate design.

The Profile Error Feedback Optimization for the Design of a Showerhead System Controlling Gas Flow Uniformity in a Thin-Film Reactor

The design of a vector showerhead in a vertical reactor involves thousands of holes on the showerhead face plate and mass transport in the reactor, and the design variables and objective are always spatial related continuous characteristic, so the discretized sequence of the design variables has too many degrees of freedom that the needed sampling points of a design of experiment or heuristic algorithm methods are hardly acceptable. In order to solve this problem, a profile error feedback (PEF) optimization method was proposed. This method employed a loop-iteration-approximation mode, and started from a guessed initial model, and then fed back the profile error of design objective, according to a weight function, to continually adjusted the design variable sequence to make the gas flow uniformity in the new model continually approximate the perfect one. The optimization case of a vector showerhead system shown that the non-uniformity of the gas flow was reduced from 0.36% to 0.03% under a typical process condition.

Dual electrodes degradation of Amaranth using a thin-film photocatalytic reactor with dual slant-placed electrodes

A dual slant-placed electrodes thin-film photocatalytic (PC) reactor was proposed and successfully applied to degrade Amaranth. In this PC reactor, both the TiO2/Ti photoanode and the Cu cathode are slant-placed in the reaction chamber, and aqueous thin-film formed on the surface of both electrodes as wastewater flowed over them. The degradation efficiency was significantly improved as a result of additional degradation at the cathode. When the TiO2 photocatalyst was irradiated with UV light, photogenerated electrons were spontaneously transferred from the anode to the cathode, driven by the electric field self-generated between the TiO2/Ti anode and the Cu cathode, based on the principle of establishing a Schottky barrier. On the Cu cathode surface, the transferred photoelectrons either reacted with dissolved oxygen to form H2O2, which then oxidized the dye, resulting in indirect oxidation decolourization, or reacted with the dye, resulting in direct reduction decolourization. The colour removal efficiency of the cathode was about half that of the photoanode. These processes together with direct oxidation of the photogenerated holes on the photoanode gave dual electrode degradation of the dye, and the degradation efficiency was significantly improved.