Continuous Flow-through Reactor Research Articles

Solar-driven chloride activation via 3D oxygen-vacancy-rich TiO2 network photoanode for ultrafast and durable purification of saline wastewater

Photoelectrochemical chloride activation (PEC-Cl) is a promising and reagent-free strategy to treat saline organic wastewater by activation of chloride (Cl–) using sunlight. However, the low efficiency and Cl– corrosion of photoelectrode, and the limited mass transfer of pollutant hinder its application. Herein we successfully solve these challenges by developing porous oxygen-vacancy-rich TiO2 nanoneedle arrays (TiO2 NNs-r400) photoanode. Under illumination, the photoinduced holes in TiO2 NNs-r400 oxidize Cl– to reactive species (e.g., HOCl, Cl•, Cl2•− and ClO•), resulting in the degradation rate of tetracycline hydrochloride (HTC, 0.861 min−1) by TiO2 NNs-r400/PEC-Cl system is 2–3 orders of magnitude higher than the state-of-the-art. Experiments and computational analysis indicate that oxygen vacancies (Ovs) on TiO2 NNs-r400 promote the photocarriers separation efficiency and more importantly, facilitate Cl– adsorption with intermediary strength and reduce the energy barriers of Cl– oxidation. Furthermore, we design a continuous flow-through PEC reactor for TiO2 NNs-r400/PEC-Cl technology. The process exhibits 100% HTC degradation (TOC = 60.23%) for over 2000 h flow-through operation, which maintains high activity in the treatment marine aquaculture wastewater with nearly zero energy consumption by directly utilize natural sunlight. In the final effluent, the toxicity of almost all degradation intermediates is decreased, and the formation of total organic chlorine is low (17.2 µg L–1). This work provides insights into Cl– activation on Ov-rich photoanode and strategy for practical application of solar energy in efficient, sustainable and eco-friendly wastewater decontamination.

Electrochemical oxidation of phenol in a PtRu/NbC membrane-based catalytic nanoreactor

Electrochemical oxidation has attracted growing attention to treat organic in wastewater. However, achieving a high reactor efficiency and harmless treatment of the toxic organics is still a significant challenge. In this work, the bimetal Pt and Ru were firstly co-electrodeposited on the surface of nanoporous niobium carbide (NbC) membranes (∼8.3 nm pore size) applying for anode in flow-through reactor for phenol electrochemical oxidation. In a continuous flow-through reactor, the single-pass removals of phenol and chemical oxygen demand (COD) were 99.7 % and 74.2 %, respectively, with a short hydraulic retention time of 342 s, demonstrating rapid phenol degradation that is an order of magnitude shorter than those reported in other studies. This excellent reactor efficiency was ascribed to a large interfacial reaction area providing by the pollutant phase-catalytic membrane-green product phase. We compared the mass transfer of flow-through and flow-by reactor testifying the high efficiency of flow-through reactor. The excellent stability of PtRu/NbC anode enable this reactor to operate 50 h stably. Moreover, the presence of low or non-toxic (catechol and acetic acid) as the residues of phenol degradation resulting from the contribution of synergistic reaction between direct and indirect oxidation process.

Construction of CoTiO3/TiO2/Ti composite catalytic membrane for degradation of tetracycline via peroxymonosulfate activation: Reactive oxygen species and electron transfer pathways

The advanced oxidation processes based on peroxymonosulfate (PMS) has shown great promise for the removal of emerging contaminants in water reuse applications. Constructing cobalt-based composite nanomaterials is an effective strategy to achieve electron transfer and reduce the leaching of cobalt ions. Here, a CoTiO3/TiO2/Ti (CTT) catalytic membrane was fabricated using TiO2 nanotubes as both template and reactant, and then was applied to activate PMS for tetracycline (TC) degradation in a continuous flow-through reactor. The CTT/PMS system showed a remarkable TC degradation efficiency of 96.99%, exhibiting anti-interference performance towards Cl−, HCO3– and humic acid in water (>90.00% degradation efficiency). It has been proved that OH, SO4−, and 1O2 existed in the CTT/PMS system, and the CTT membrane served as a medium for mediating the electron transfer from TC to PMS. Density functional theory calculations indicated that the construction of a composite structure of CoTiO3 and TiO2 successfully enhanced the activation of PMS by the electron transfer from Ti atoms of TiO2 to Co sites. We proposed three potential degradation pathways for TC, followed by toxicity analysis of the intermediate products. After being exposed to an initial TC concentration of 20 mg/L and a membrane flux of 600 LMH for 30 hours, the CTT catalytic membrane exhibited a TC degradation rate exceeding 92.23% and mineralization rate surpassing 64.43%. This work supplied a new approach for fabricating cobalt-based catalytic membrane for PMS activation, with potential applications in water reuse.

Low-cost and large mass producible phenolic resin for water disinfection and antibacterial coating under weak visible light LED or sunlight irradiation

In present study, we for the first time discovered the photocatalytic water disinfection and antibacterial ability of phenolic-formaldehyde (PR) resins irradiated by LED lamp or natural sunlight in various application modes. The novel narrow band-gap, low-cost and large mass easily producible resin photocatalysts exhibit advanced and stable Escherichia coli (E. coli) inactivation performance, which is better than some well-known metal and non-metal based visible light photocatalysts under the identical condition. We have provided a proof-of-concept demonstration of its practical application feasibility for water purification in both immobilized plastic bag and continuous flow-through reactor under weak LED lamp or natural sunlight irradiation. Furthermore, the PR resin coating film exhibits remarkable E. coli deactivation property under weak LED lamp irradiation. This work provides a new approach for developing resin-based products with antibacterial function or solar water purification products for practical use.

Photocatalytic inactivation of airborne bacteria in a polyurethane foam reactor loaded with a hybrid of MXene and anatase TiO2 exposing {0 0 1} facets

A hybrid of TiO2 exposing {001} facets and monolayer Ti3C2Tx nanosheet (MXene) was synthesized, characterized and used as a photocatalyst in this study. The introduction of MXene (3.4 wt%) helped to reduce the recombination of photo-induced electrons and holes, and thus enhanced the photocatalytic activity by 30%. A continuous flow-through reactor loaded with the as-prepared photocatalyst coated onto polyurethane foam was developed to inactivate airborne bacteria. The photocatalytic inactivation efficiency of airborne Escherichia coli (E. coli) achieved 3.4 lg order under ultraviolet (UV) irradiation at 254 (UV254), which was superior to that using UV254-only treatment with 2.5 lg order under the same operating condition (95% relative humidity and retention time of 4.27 s). The effect of humidity and bacteria species on inactivation performance was also investigated. The thick cell membrane could protect bacteria from photocatalytic oxidation while high humidity increased the photocatalytic inactivation efficiency by generating more reactive oxygen species. The phenomena of photo reactivation and dark repair of airborne E. coli using UV254-only treatment was observed. However, no reactivation occurred after UV photocatalytic inactivation, and even a continuous decline under visible light. These results suggested a different inactivation mechanism between UV irradiation and UV photocatalysis that the former inactivated bacteria by damaging their DNA, whereas photocatalysis physically damaged their cell structure.

Electrochemical degradation of herbicide diuron on flow-through electrochemical reactor and CFD hydrodynamics simulation

An energy-efficient continuous flow-through electrochemical reactor (FT-ER) equipped with PbO2 filter anodes is designed and employed for electrochemical elimination towards herbicide diuron in the aquatic environment. Boosting performances, including substantially higher electrochemical mineralization kinetics and lower energy consumption, could be realized on the FT-ER compared with the traditional flow-by model. The effect of current density and flow rate on the degradation efficiency is also investigated. The glorious degradation kinetics could be ascribed to the large electrochemical surface area, strong generation power of reactive oxidants, and enhanced mass transfer process derived from the filter structure. Furthermore, we establish the computational fluid dynamics simulation to elucidate the dynamic flow behavior of the electrolyte, including fluid velocity and turbulent intensity distribution. The profound influence of FT-ER for the herbicide diuron removal stems from the homogenization of electrolyte flux and turbulence promoter of the filter structure. Finally, the continuous flow-through configuration exhibits excellent elimination performances, uniform fluid dynamics together with good stability. The filter anodes present a promising option for electrochemical treatment towards diverse organic pollutants in the aquatic environment and would be benefit to the evolution of cost-efficient electrochemical treatment techniques and reactors.

Pd@COF-QA: a phase transfer composite catalyst for aqueous Suzuki–Miyaura coupling reaction

A COF-based phase transfer catalyst and its continuous flow-through reactor was prepared. The obtained Pd@COF-QA can highly promote the Suzuki–Miyaura coupling reaction in water under mild conditions even at gram scale level.

Integration of aerobic granulation and UV/H2O2 processes in a continuous flow system for the degradation of sulfolane in contaminated water

Aerobic granulation and UV/H2O2 in a continuous flow-through reactor can effectively degrade emerging contaminates, such as sulfolane.

A new continuous flow-through structured reactor for the photodegradation of aqueous contaminants

A flow-through photo reactor with a stainless steel mesh-supported ZnO catalytic disc has been designed in this work. The preparation method of the catalyst includes the use of Triton™ X-100 and methylene blue (MB) in order to enhance the homogeneity of the ZnO and its adhesion to the mesh. The catalysts exhibit a high surface area (∼100 m2/g). The photocatalytic reaction is restricted to the most external non-polar edges of the ZnO nanosheets due to the low pH of the MB solution and to the fact that the polar surfaces are hydrophobic. Despite this, the performance of the flowthrough reactor is superior to that of other micro fluidic systems. The catalyst undergoes a slight deactivation during the reaction, though the activity can be restored, without causing any structural changes, by passing water through the catalyst under UV irradiation. The loss of ZnO through photocorrosion is low, especially when compared to the loss experienced by the same catalyst prepared without using methylene blue.

Preparation and characterization of phosphotungstic acid/PVA nanofiber composite catalytic membranes via electrospinning for biodiesel production

A nanofiber composite catalytic membrane for biodiesel production was prepared from phosphotungstic acid (PWA)/poly(vinyl alcohol) (PVA) via electrospinning on a substrate of non-woven fabric. The effects on the nanofiber structure and catalytic performance by PVA concentration and PWA content were studied, respectively. SEM images showed that the surface of PWA/PVA nanofibers was smooth and homogeneous with an average fiber diameter of 157.2nm when PVA concentration was 12wt% and PWA content was 20wt%. FTIR analysis indicated that there existed the interaction between PWA and PVA in the nanofibers. DSC and TG analysis revealed that PWA/PVA nanofiber had a good thermal stability. The nanofiber membrane had a higher activity and better site accessibility than that of commercially ion-exchange resin (NKC-9) because both reaction rate constant (2.647min−1) and effectiveness factor (0.92min−1) of nanofiber membrane were higher than that of NKC-9. The stability test of nanofiber membrane suggested that the conversion could remain stable for 10days in a continuous flow-through reactor for biodiesel production.

Electrochemical recycling of gold nanofibrous membrane as an enzyme immobilizing carrier

A gold nanofibrous membrane was shown to be an enzyme-immobilizing carrier that can be recycled on-site in a continuous flow-through reactor using a simple electrochemical treatment. The membrane was prepared by electrospinning a polyacrylonitrile/gold salt solution, followed by electroless gold plating. Laccase, used as a model enzyme, was immobilized on the gold membrane surface by a combination of formation of amino-terminated self-assembled monolayers and glutaraldehyde treatment. Enzyme desorption at neutral pH was confirmed by a 98% decrease in enzymatic activity, based on oxidation of a 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) substrate, after electrochemical treatment for desorption, and surface characterization using X-ray photoelectron spectroscopy. The enzymatic activity after re-immobilization on the membrane was restored to 90%, and decreased to 1.0% after redesorption. These results showed that recycling of the gold nanofibrous membrane as an enzyme-immobilizing carrier was possible. The laccase-immobilized membrane was used in a flow-through reactor; the activities of the immobilized and re-immobilized enzymes on the membrane were 62.7% and 58.5% of the respective initial activities after operation for 7d.

Kinetics of Oxygen Delignification of High-Kappa Pulp in a Continuous Flow-Through Reactor

The delignification kinetics and delignification/carbohydrates degradation selectivity of oxygen delignification (O-delignification) of a high kappa number (HKn) pine kraft pulp (kappa 65) were stu...

Obtaining jet fuel components by decarboxylation of crude oil acids in the presence of nanosized titanium dioxide

Crude oil acids, isolated from high-acid crude oil, were decarboxylated in a continuous flow-through reactor in the presence of nanosized titanium dioxide. We studied the effect of the reaction temperature on the acid number of the product and the acid conversion. The product obtained, with low acidity and high calorific value and representing a mixture of naphthenic hydrocarbons, is proposed as a component of jet fuels.

Development of a high performance electrochemical cofactor regeneration module and its application to the continuous reduction of FAD

Abstract Technical reactor limitations and low productivities have been shown to limit the implementation of electroenzymatic syntheses beyond lab-scale. One possible solution is a continuous flow-through reactor based on electrochemical plate and 6 frame filter press cells, as proposed in this study. With the aim of maximizing electroenzymatic productivities, the developed reactor set-up allows high electrochemical cofactor regeneration rates using porous, three-dimensional reticulated vitreous carbon electrodes with exceptionally large surface areas up to 19,685 m2 m−3. This system provides increased mass transfer rates and flavin adeninedinucleotide (FAD) was reduced at rates up to 93 mM h−1. The electrochemical FAD reduction was coupled to the styrene monooxygenase (StyA) catalyzed (S)-epoxidation of styrene. Electroenzymatic productivities increased with FAD reduction rates up to 1.3 mM h−1. This set-up now set the stage for efficient in vitro FAD regeneration and allows a broad electrochemical application of flavin dependent enzymes as biocatalysts.

A novel arsenic removal process for water using cupric oxide nanoparticles

Recent studies suggest that the cupric oxide (CuO) nanoparticles effectively adsorb aqueous arsenic species under a wide range of water chemistries. However, to develop CuO nanotechnology to a field application level, further studies are necessary. Batch adsorption kinetic experiments were conducted to determine the time course of uptake of arsenic by CuO nanoparticles. A reactor with CuO nanoparticles was developed to conduct continuous flow-through experiments to filter arsenic from groundwater samples. Groundwater samples spiked with 100μg/L of arsenic were passed through (1L/h) the flow-through reactor. Samples from the flow-through reactor were collected at a regular interval and analyzed for arsenic and other chemical components (e.g., pH, major and trace elements). The CuO nanoparticles adsorbed with arsenic were regenerated with a sodium hydroxide (NaOH) solution and tested again in the flow-through reactor. Three natural groundwater samples with above 10μg/L of arsenic were also tested with the flow-through reactor. The arsenic adsorption process by CuO nanoparticles was kinetically rapid and followed the pseudo-second-order rate. The continuous flow-through reactor with CuO nanoparticles was effective in filtering arsenic from spiked or natural groundwater. The regenerated CuO nanoparticles were also effective in filtering arsenic from groundwater. Arsenic mass balance data from regeneration studies suggested that 99% of input arsenic concentration was recovered. The CuO nanoparticle treatment did not show any discernible effects on the chemical quality of groundwater samples. Results of this study suggest that CuO nanoparticles show potential for developing a simple process for field applications to remove arsenic from water.

Direct flue gas CO2 mineralization using activated serpentine: Exploring the reaction kinetics by experiments and population balance modelling

Abstract Avoiding CO 2 emissions to the atmosphere by its safe and permanent storage is required for all options within the CCS framework. Only mineral carbonation allows for a sequestration process, where the carbon is rapidly converted to its chemically most stable form, a carbonate. So far, most researchers looking into mineral carbonation focused on routes that involve an aqueous medium, where carbonation takes place under an atmosphere of pure CO 2 , either in a single or multi-step process. We have started to investigate a novel approach to aqueous mineral carbonation where the costly capture step is avoided by the direct mineralization of flue gas CO 2 at the point source. For the present study, we have built a set-up to perform mineralization experiments under a variety of conditions in both batch or flow-through mode. The residence times of the reactor solution and gas phase involved can be freely adjusted: The design allows for flowing both the feed solution and the flue gas continuously through an autoclave that contains a sample of activated serpentine. The use of online ion chromatography and in-situ Raman spectroscopy allows monitoring magnesium concentration as well as the solids and dissolved phases throughout an experimental run. A population balance equation model has been developed and its solution was coupled with the continuous flow-through reactor model. The experimental data serves as input to the model in order to regress reaction rates under a variety of operating conditions. A precise knowledge of the dissolution and precipitation kinetics is required for the optimal design and scale-up of the mineralization process. Moreover, the ultimate particle size distribution is of key importance for mineralization product processing and product applications.

A device that converts aqueous ammonia into nitrogen gas

A photoelectrocatalytic oxidation (PECO) 3 3 Nonstandard abbreviations used in text: PECO: Photoelectrocatalytic oxidation. device was developed for converting aqueous ammonia into nitrogen gas. The device uses a germicidal UV lamp to activate a titania (TiO 2)-coated anode (photoanode) that is connected to a titanium or platinum wire cathode to form an electrolytic cell. When a small bias (∼2 V DC) was applied between the anode and cathode, ammonia (−3 oxidation state) was oxidized primarily into nitrogen gas (0 oxidation state) rather than nitrite (+3 oxidation state) or nitrate (+5 oxidation state). The ammonia oxidation rate changed as a function of the crystalline structure of the titania coating on the anode, the salinity of the water, the applied voltage, and the disruption of boundary layers near the photoanode surface. There was no ammonia removal in water without at least some NaCl in solution, suggesting that the device works by converting chloride ions into chlorine and hypochlorous acid, which then react with ammonia to form nitrogen gas. Varying the pH between pH = 5 and pH = 10 had no effect on the rate of ammonia removal. A continuous flow-through PECO reactor was tested using aquariums spiked with ammonium chloride or stocked with seawater-adapted tilapia fed a high protein diet, and found to effectively remove ammonia and limit nitrite and nitrate accumulation in the tanks.

Kinetics of biotite dissolution and Fe behavior under low O 2 conditions and their implications for Precambrian weathering

Biotite dissolution experiments were carried out to better understand the dissolution kinetics and Fe behavior under low O 2 conditions, and to give an insight into the Precambrian weathering. Mineral dissolution with a continuous flow-through reactor was employed at 25 °C for up to 65 days varying partial pressure of atmospheric oxygen ( PO 2), pH (6.86 and 3.01) and Fe content in mineral (1.06 and 0.11 mol of Fe per O 10(OH,F) 2 for biotite and phlogopite, respectively) independently for the examination of their effects on biotite dissolution. Low PO 2 conditions were achieved in a newly developed glove box ( PO 2 ⩽ 6 × 10 −4 atm; referred to as anoxic conditions), which was compared to the present, ambient air conditions (0.2 atm of PO 2; oxic conditions). The biotite dissolution rate was slightly faster under anoxic conditions at pH 6.86 while it was not affected by PO 2 at pH 3.01. There was no direct effect of Fe content on dissolution rate at pH 6.86 while there was a small difference in dissolution rate between biotite and phlogopite at pH 3.01. The 1.5 order-of-magnitude faster release rate of Fe under anoxic conditions for biotite dissolution at pH 6.86 resulted from the difference in ratio of Fe 3+ precipitates remaining in the reactor to Fe dissolved (about 60% and 100% under anoxic and oxic conditions, respectively), which is caused mainly by the difference in PO 2. The results infer that the Fe 2+ and Fe 3+ contents in the Paleoproterozoic paleosols, fossil weathering profiles, are reflected by atmospheric oxygen levels at the time of weathering.

Kinetics of UO2(s) Dissolution in the Presence of Hypochlorite, Chlorite, and Chlorate Solutions

AbstractThe influence of hypochlorite, chlorite and chlorate in the UO2dissolution rate has been studied experimentally using a continuous flow-through reactor. Uranium concentration in each outflow solution was measured as a function of time and dissolution rates were determined once the steady-state was reached. The results obtained show that the influence of the hypochlorite anion concentration on the UO2dissolution rate can be expressed by the following empirical equationrdiss= 10-8.7±0.1•[ClO-]0.28±0.04The dissolution rates obtained in this work were higher than those previously determined in presence of either oxygen or hydrogen peroxide using the same experimental methodology.In contrast, neither chlorate nor chlorite had any significant effect on the UO2dissolution rates under the experimental conditions of this work.

Leaching behaviour of non-irradiated and irradiated HTR UO2-ThO2fuel particles under reducing conditions

ABSTRACTThe dissolution of irradiated HTR UO2-ThO2fuel particle under reducing conditions was studied using a continuous flow-through reactor and compared to the dissolution of unirradiated fuel particle in the same condition. The irradiated fuel particle was leached for more than eight months. A fast137Cs release was observed, corresponding to a labile fraction (“instant release fraction”). Then, a congruent leaching of137Cs and90Sr was measured corresponding to a matrix dissolution rate equal to 1.7 mg/m2/d. A slower release of238Pu probably due to sorption phenomena is observed. Dissolution rates are 100-2000 times higher than for unirradiated material. We can conclude that alpha-radiolysis is responsible for this increase due to local oxic conditions. However we cannot exclude that due to irradiation the accessible surface area has been increased as well.The coating of this irradiated particle was equally studied to determine the presence of different radionuclides and their leaching properties of leaching