Open Reactor Research Articles

Comparative study of electrochemical water treatment processes for a tannery wastewater effluent

Comparison of tannery wastewater treatment results of electrocoagulation (EC), electro-oxidation (EOx), electro-Fenton (EF) and photoelectro-Fenton (PEF) processes using two current densities was performed and employed no only to assess the best electrochemical approach but also to have elements to suggest a combined and cost effective process. In this way, iron plates were used as the anode and cathode in the EC tests. For the EOx process, a boron-doped diamond (BDD) thin-film electrode was used as the anode, and an iron plate was employed as the cathode. For the EF and PEF treatments, both electrodes were of BDD and H2O2 was produced by O2 reduction at the cathode surface. Electrolytic trials were carried out in stirred open tank reactors containing 250mL of wastewater applying either 65 or 111mAcm−2. In PEF trials, the wastewater was irradiated using a 6W UVA light source. The characterization of the sludge generated in the EC process showed that it was not dangerous for the environment. Total Organic Carbon (TOC) removal values were larger at the highest density. Higher mineralization on the other hand, was found in EF and PEF when the concentration of Fe2+ was 3.0 instead 1.0mM. Comparison of the methods revealed that their efficiency to remove the organic pollutant increased in the order EOx<EC∼EF<PEF after 180min of electrolysis. Furthermore, the information obtained from the study, also allowed designing a combined strategy aimed to produce an effluent suitable for discharge. The combination of EC followed by PEF was also studied. The results showed that the EC/PEF treatment gave higher organic removal than EC and was more economic than PEF, being able to yield 90% TOC reduction of the tannery wastewater.

Microscale enzyme reactors comprising gold nanoparticles with immobilized trypsin for efficient protein digestion

Microscale sample processing devices for application in bioanalysis and proteome related studies have undergone rapid advancements during the recent years. Several techniques for the preparation of chip-based and capillary-based microfluidic systems and their modification with desired functionalities have been reported. The use of microfluidic devices allow easy processing of extremely small sample quantities with low reagent consumption and offer high surface areas and surface-to-volume ratios. Microscale sample processing devices find application in various research fields such as chemical analysis, kinetic studies, and bioanalytical research. In MS-based proteomics, enzymatic digestion is one of the key steps in the identification of proteins and their posttranslational modifications. However, this is usually the slowest step in the analysis workflow. Thus, the development of suitable devices and methods capable of performing efficient protein digestion more rapidly has become an area of considerable interest. The immobilization of proteolytic enzymes on different kinds of stationary phases, such as monoliths, microparticles and nanoparticles and inner surface of sample transfer capillaries has shown promising results. On the other hand, problems associated with the fabrication and applicability of different stationary phases may pose some challenges, such as monolithic supports involve time consuming fabrication procedures. Similarly, particle-based supports usually involve multistep synthesis and require extended incubation times for protein digestion. Hence, in order to accelerate digestion, other techniques such as microwave irradiation have been employed, which will further complicate the experimental setup. Alternatively, open channel microreactors comprising immobilized enzymes have appeared as a promising alternative, offering minimal restriction over the flow rates. Krenkova et al. prepared open tubular enzyme-immobilized reactors by coupling of trypsin and pepsin to the inner wall of a fused silica capillary. Stigter et al. reported the development of an open tubular trypsin reactor based on amino-modified and carboxyl-modified dextran. Later, the same group prepared a pepsin-immobilized reactor in a dextran-modified fused silica capillary for online protein digestion. The coating of the capillary wall with dextran hydrogel was carried out in order to load higher amounts

Coupled reaction and solvent extraction process to form Li2CO3: Mechanism and product characterization

A coupled reaction and solvent extraction process to produce Li2CO3 from LiCl and CO2 is proposed. The aqueous reaction occurs with difficulty and is not spontaneous at 298 K. To ensure the continuous reaction between LiCl and CO2 to produce Li2CO3, it is necessary to remove HCl. Experiments conducted in an open reactor at room‐temperature showed that the product sample was pure Li2CO3 with a particle‐size distribution in two regions and a larger number of small crystals. The large and small crystals were obtained by radial growth in the free aqueous phase and in water‐in‐oil structures with growth space constraints, respectively. Factors influencing the particle‐size distribution and Li2CO3 morphology were investigated. A short reaction time, large phase ratio (O/A), low–temperature, and surfactant addition (TritonX‐100) can increase the number of small particle crystals and reduce the number and volume of large particle crystals. © 2013 American Institute of Chemical Engineers AIChE J, 60: 282–288, 2014

Continuous Acid Blue 45 decolorization by using a novel open fungal reactor system with ozone as the bactericide

To maintain long-term lignin-degrading enzyme production under non-sterile conditions was a key to the technical application of white rot fungi in wastewater treatment. In this work, a novel open fungal reactor system with ozone as the bactericide, and using immobilized Phanerochaete chrysosporium, was built and operated continuously to produce the manganese peroxidase and decolorize the Acid Blue 45. The results showed that an average of 84% Acid Blue 45 decolorization, the manganese peroxidase production with its activity ranging from 63UL−1 to 5UL−1, was achieved during about 25 days system continuous operation. The contaminating bacteria in the reactor can be controlled at a level of 4.65×104CFUml−1 that did not adversely affect the fungal activity. The result of this study provides a new practical way for future design and operation of white-rot fungi reactor under non-sterile conditions.

Analysis of the iodine gas phase produced by interaction of CsI and MoO3 vapours in flowing steam

In case of severe accident in a water-cooled nuclear reactor, the amount of gaseous iodine released from the primary circuit is of particular concern because it can have a direct impact on the short-term iodine source term to the environment. As revealed by the Phebus FPT tests, assessment of the iodine forms at the break is a complex issue that requires to take into account not only the thermal and flow conditions in the circuit but also the behaviour of several elements such as caesium and molybdenum involved in iodine chemistry at high temperature. Moreover, reactions between these elements and with the carrier gas could be kinetically-limited due to the low concentrations and the short residence time of the fission products in the primary circuit coupled to the strong thermal gradients encountered in this part of the reactor. In order to reduce the uncertainties in the fraction of gaseous iodine, experimental and modelling studies have been launched in the framework of the international CHIP program. The work presented in this paper is part of this program and aims to investigate the effect of molybdenum using an open flow reactor where MoO3 and CsI vapours are injected under steam/argon atmosphere. In these conditions, the experiments clearly demonstrate that molybdenum increases the fraction of gaseous iodine released at low temperature and show that this effect is highly sensitive to the Mo/Cs ratio. Caesium polymolybdates identified in the solid state by Raman microspectroscopy are consistent with the species of the Cs2MoO4–MoO3 diagram suggesting that some part of caesium could be present in the gas phase as Cs2MoO4. Calculations based on thermodynamic equilibrium in the gaseous phase give the right trend but predict HI as the major species whereas iodine is recovered mainly under molecular form (I2). Iodine speciation is better accounted with the new kinetic scheme developed for the {I, O, H} system and recently implemented in the ASTEC code.

Comprehensive model of microalgae photosynthesis rate as a function of culture conditions in photobioreactors

In this paper, the influence of culture conditions (irradiance, temperature, pH, and dissolved oxygen) on the photosynthesis rate of Scenedesmus almeriensis cultures is analyzed. Short-run experiments were performed to study cell response to variations in culture conditions, which take place in changing environments such as outdoor photobioreactors. Experiments were performed by subjecting diluted samples of cells to different levels of irradiance, temperature, pH, and dissolved oxygen concentration. Results demonstrate the existence of photoinhibition phenomena at irradiances higher than 1,000μE/m(2)s; in addition to reduced photosynthesis rates at inadequate temperatures or pH-the optimal values being 35°C and 8, respectively. Moreover, photosynthesis rate reduction at dissolved oxygen concentrations above 20mg/l is demonstrated. Data have been used to develop an integrated model based on considering the simultaneous influence of irradiance, temperature, pH, and dissolved oxygen. The model fits the experimental results in the range of culture conditions tested, and it was validated using data obtained by the simultaneous variation of two of the modified variables. Furthermore, the model fits experimental results obtained from an outdoor culture of S. almeriensis performed in an open raceway reactor. Results demonstrate that photosynthetic efficiency is modified as a function of culture conditions, and can be used to determine the proximity of culture conditions to optimal values. Optimal conditions found (T = 35°C, pH = 8, dissolved oxygen concentration <20mg/l) allows to maximize the use of light by the cells. The developed model is a powerful tool for the optimal design and management of microalgae-based processes, especially outdoors, where the cultures are subject to daily culture condition variations.

Pilot study of the removal of individual trihalomethanes (THMs) from chlorinated drinking water by GAC adsorption - Galatsi water treatment plant, Athens, Greece

&lt;p&gt;The objective of this pilot study was to evaluate the performance of Powdered Activated Carbon (PAC) for the removal of individual trihalomethanes (THMs) from chlorinated drinking water, Athens, Greece. The pilot treatment facility was located at the Water Treatment Plant of EYDAP (Athens Water Supply and Sewerage Company) in Galatsi, Athens, and consisted of two mixing tanks operating as open batch reactors, which were fed with chlorinated water from the overflow of the sedimentation tanks. Experimental cycles were performed, with different PAC doses ranging from 5 to 50 mg L-1 and with contact times 30 and 60 min for each cycle. Water samples taken at the start of each cycle and after contact with PAC, were analysed for individual THMs and Dissolved Organic Carbon (DOC). Bromide, free residual chlorine, pH and temperature were also measured. From the experimental results, it was shown that all THMs concentrations were decreased after PAC contact, the decrease being higher for higher PAC dose and higher contact time, with few exceptions. This fact probably indicates that adsorption rate plus volatilisation rate of THMs overcame formation rate, in most cases. It was also concluded that volatilisation and possible formation reactions of THMs had probably a more apparent effect to the total removal of most THMs at low PAC doses and low contact time. At higher PAC doses and higher contact time, PAC adsorption probably had an increased contribution to THMs removal, because of the larger carbon surface area and the longer contact time, resulting in higher adsorbed mass according to adsorption theory. By using isotherm results of individual THMs on activated carbon by other researchers, the theoretically adsorbed mass of THMs per g of PAC was roughly estimated and compared with the measured removed mass of THMs per g of PAC at PAC dose 50 mg L-1 and contact time 60 min for most THMs, on the assumption of equilibrium achievement. The removed mass of THMs by PAC appeared much higher than the theoretically adsorbed, especially for the most volatile members. The difference was attributed to volatilisation taking place in the open mixing tanks. In conclusion, the practical results from the application of PAC for the removal of THMs are much better than expected from single adsorption by PAC. Volatility of THMs, especially of chloroform (TCM), substitutes for weak adsorbability and gives increased removal. The influent DOC was almost constant in all experiments. The removal of DOC was generally higher for increased PAC dose and contact time. Although equilibration cannot have happened for DOC, the mass removal of DOC per g of PAC was higher by more than two orders of size than that of the smaller and in lower concentration THMs, as expected.&lt;/p&gt;

Carbon and nutrient removal from centrates and domestic wastewater using algal–bacterial biofilm bioreactors

The mechanisms of carbon and nutrient removal in an open algal-bacterial biofilm reactor and an open bacterial biofilm reactor were comparatively evaluated during the treatment of centrates and domestic wastewater. Comparable carbon removals (>80%) were recorded in both bioreactors, despite the algal-bacterial biofilm supported twice higher nutrient removals than the bacterial biofilm. The main carbon and nitrogen removal mechanisms in the algal-bacterial photobioreactor were assimilation into algal biomass and stripping, while stripping accounted for most carbon and nitrogen removal in the bacterial biofilm. Phosphorus was removed by assimilation into algal-bacterial biomass while no effective phosphorous removal was observed in the bacterial biofilm. Carbon, nitrogen and phosphorus removals of 91 ± 3%, 70 ± 8% and 85 ± 9%, respectively, were recorded in the algal-bacterial bioreactor at 10d of hydraulic retention time when treating domestic wastewater. However, the high water footprint recorded (0.5-6.7 Lm(-2)d(-1)) could eventually compromise the environmental sustainability of this microalgae-based technology.

Prototype thermochemical heat storage with open reactor system

Thermochemical (TC) heat storage is an interesting technology for future seasonal storage of solar heat in the built environment. This technology enables high thermal energy storage densities and low energy storage losses. A small-scale laboratory prototype TC storage system has been realized at ECN, applying an open sorption system concept. The packed bed contains 17dm3 of sorption material and is capable of generating 150W of thermal power. An effective energy storage density of approximately 0.5GJ/m3 was obtained.

Radiological performance of hot water layer system in open pool type reactor

The paper presents the calculated dose rate carried out by using MicroShield code to show the importance of hot water layer system (HWL) in 22MW open pool type reactor from the radiation protection safety point of view. The paper presents the dose rate profiles over the pool surface in normal and abnormal operations of HWL system. The results show that, in case of losing the hot water layer effect, the radiation dose rate profiles over the pool surface will increase from values lower than the worker permissible dose limits to values very higher than the permissible dose limits.

Large‐Scale Production of Hierarchical TiO2 Nanorod Spheres for Photocatalytic Elimination of Contaminants and Killing Bacteria

We report a facile non-hydrothermal method for the large-scale production of hierarchical TiO(2) nanorod spheres for the photocatalytic elimination of contaminants and killing bacteria. Crescent Ti/RF spheres were prepared by deliberately adding titanium trichloride (TiCl(3)) to the reaction of resorcinol (R) and formaldehyde (F) in an open reactor under heating and stirring. The hierarchical TiO(2) nanorod spheres were obtained by calcining the crescent Ti/RF spheres in a furnace in air to burn off the RF spheres. This method has many merits, such as large-scale production, good crystallisation of TiO(2), and good reproducibility, all of which are difficult to realise by conventional hydrothermal methods. The calcination temperature plays a significant role in influencing the morphology, crystallisation, porosity, Brunauer-Emmett-Teller (BET) specific surface area, and hierarchy of the TiO(2) nanorod spheres, thus resulting in different photocatalytic performances under UV light and solar light irradiation. The experimental results have demonstrated that the hierarchical TiO(2) nanorod spheres obtained after calcination of the crescent Ti/RF spheres at different temperatures displayed similar photocatalytic activities under irradiation with UV light. We attribute this to a balance of opposing effects of the investigated factors. A higher calcination temperature leads to greater light absorption capability of the TiO(2) nanorod spheres, thus resulting in higher photocatalytic antibacterial activity under solar light irradiation. It is also interesting to note that the hierarchical TiO(2) nanorod spheres displayed intrinsic antibacterial activity in the absence of light irradiation, apparently because their sharp outward spikes can easily pierce and penetrate the walls of bacteria. In this study, the sharpest hierarchical TiO(2) nanorod spheres were obtained after calcination at 500°C, and these exhibited the highest antibacterial activity without light irradiation. A higher calcination temperature proved detrimental to the sharpness of the TiO(2) nanorods, thus reducing their intrinsic antibacterial activity.

Kinetic Modeling of Arab Light Vacuum Residue Upgrading by Aquaprocessing at High Space Velocities

Aquaprocessing (AQP) is a novel method that offers higher conversion level under asphaltenes stability limit. It is a process of steam catalytic cracking using unsupported ultradispersed catalyst. Following a 2011 published work by Fathi and Pereira on upgrading a paraffinic residuum from Arab Light Vacuum Residue (ALVR) by AQP, this work investigates a proposed lumped kinetic model for the upgrading of ALVR via AQP for the first time. The model is evaluated based on experimental results conducted in a continuous upflow open tubular pilot-plant reactor under short-space times and under conditions distant from coke formation. The proposed model is based on five cascaded lumps generated at and below the asphaltenes stability limit: 540 °C+ ALVR, VGO (455–540 °C), distillates (204–455 °C), naphtha (IBP–204 °C), and gases. The model compositions are found close to the experimental values with mean absolute percentage errors (MAPEs) of <5.5%.

A nanoliter-scale open chemical reactor

An open chemical reactor is a container that exchanges matter with the exterior. Well-mixed open chemical reactors, called continuous stirred tank reactors (CSTR), have been instrumental for investigating the dynamics of out-of-equilibrium chemical processes, such as oscillations, bistability, and chaos. Here, we introduce a microfluidic CSTR, called μCSTR, that reduces reagent consumption by six orders of magnitude. It consists of an annular reactor with four inlets and one outlet fabricated in PDMS using multi-layer soft lithography. A monolithic peristaltic pump feeds fresh reagents into the reactor through the inlets. After each injection the content of the reactor is continuously mixed with a second peristaltic pump. The efficiency of the μCSTR is experimentally characterized using a bromate, sulfite, ferrocyanide pH oscillator. Simulations accounting for the digital injection process are in agreement with experimental results. The low consumption of the μCSTR will be advantageous for investigating out-of-equilibrium dynamics of chemical processes involving biomolecules. These studies have been scarce so far because a miniaturized version of a CSTR was not available.

Uncertainty analysis of criticality safety for the plate type fuel assembly storage rack

To evaluate the criticality safety of the fresh and the spent fuel storage racks in an open pool type research reactor designed by KAERI, the upper subcriticality limit (USL) analysis was carried out. First, the bias and its uncertainty of MCNP code system with ENDF/B-VII library were evaluated using the calculation results of the 183 benchmark experiments. The criticality calculations for the fuel storage rack are carried out under a normal state, an increased water temperature, a fuel assembly drop, and an eccentric insertion which can affect the criticality. Considering biases and uncertainties for the MCNP code system, abnormal conditions, and the manufacturing tolerance of the cell tube thickness, the USL value that can guarantee sufficient subcriticality is determined. It was found that the criticality of the fresh and the spent fuel storage racks currently designed satisfy the USL condition. Additionally, it was concluded that the pitch size of a fresh fuel storage rack can be reduced for efficient space availability, and even under a worst case in which the fresh storage rack is surrounded by a lower water density and the smallest pitch size satisfies the USL conditions.

Effect of Dissolved Oxygen Tension and Agitation Rates on Sulfur-Utilizing Autotrophic Denitrification: Batch Tests

The effect of dissolved oxygen (DO) and agitation rate in open and closed reactors was examined for sulfur-utilizing autotrophic denitrification. The reaction rate constants were determined based on a half-order kinetic model. Declining denitrification rate constants obtained for open reactors those of 8.46, 8.03, and 2.18 for 50 mg NO(3) (-)-N/L, while 11.12, 9.14, and 0.12 mg(1/2)/L(1/2) h were for 100 mg NO(3) (-)-N/L at agitation speeds of 0, 100, and 200 rpm. In closed reactors, the ever-increasing denitrification rates were 10.13, 22.56, and 37.03, whereas for the same nitrate concentrations and speeds the rates were 13.17, 15.63, and 26.67 mg(1/2)/L(1/2) h. The rate constants correlated well (r ( 2 ) = 0.89-0.99) with a half-order kinetic model. In open reactors, high SO(4) (2-)/N ratios (8.02-75.10) while in closed reactors comparatively low SO(4) (2-)/N ratios (6.10-13.39) were obtained. Sulfur oxidation occurred continuously in the presence of DO, resulting in mixed cultures acclimated to sulfur and nitrate. SO(4) (2-) was produced as an end product, which reduced alkalinity and lowered pH over time. Furthermore, DO inhibited sulfur denitrification in open reactors, while agitation in closed reactors increased the rate of denitrification.

Effect of the growth conditions on the structural properties of CuInSe2 thin films obtained by the technique of close spaced vapor transport

Thin films of polycrystalline CuInSe2 were deposited on Pyrex substrates using a simple system of close spaced vapor transport (CSVT). The used CSVT system is an open horizontal reactor, this does not require vacuum, a gas flow is enough. During the growth phase, the CSVT system is continuously crossed by argon gas. A study on the influence of the source temperature and the deposition duration on the structural properties of the deposited films is reported. Analyses by X-ray diffraction have shown that these films are polycrystalline and have a chalcopyrite structure. The preferential orientation of the (112) plane was obtained for the films deposited at 550 ∘C. From the X-ray spectra we calculated the lattice parameters a and c, the ratio c/a was found to be close to 2. The characterization of the deposited films by an energy dispersion spectrometer (EDS) has shown that their chemical composition is quasistoichiometric with a ratio Cu/In varying from 0.96 to 1.10. Analysis with a scanning electron microscope (SEM) of the deposited films surface has shown that those slightly rich in indium present a more homogeneous morphology and smaller crystallites sizes than the films slightly rich in copper. The measurement of the photoconductivity of the prepared compound has allowed us to determine the value of its gap at room temperature. It was found to be close to 0.99 eV.

Atoms of multistationarity in chemical reaction networks

Chemical reaction systems are dynamical systems that arise in chemical engineering and systems biology. In this work, we consider the question of whether the minimal (in a precise sense) multistationary chemical reaction networks, which we propose to call ‘atoms of multistationarity,’ characterize the entire set of multistationary networks. Our main result states that the answer to this question is ‘yes’ in the context of fully open continuous-flow stirred-tank reactors (CFSTRs), which are networks in which all chemical species take part in the inflow and outflow. In order to prove this result, we show that if a subnetwork admits multiple steady states, then these steady states can be lifted to a larger network, provided that the two networks share the same stoichiometric subspace. We also prove an analogous result when a smaller network is obtained from a larger network by ‘removing species.’ Our results provide the mathematical foundation for a technique used by Siegal- Gaskins et al. of establishing bistability by way of ‘network ancestry.’ Additionally, our work provides sufficient conditions for establishing multistationarity by way of atoms and moreover reduces the problem of classifying multistationary CFSTRs to that of cataloging atoms of multistationarity. As an application, we enumerate and classify all 386 bimolecular and reversible two-reaction networks. Of these, exactly 35 admit multiple positive steady states. Moreover, each admits a unique minimal multistationary subnetwork, and these subnetworks form a poset (with respect to the relation of ‘removing species’) which has 11 minimal elements (the atoms of multistationarity).

Modelling pH oscillators in open, semi-batch and batch reactors

The general model developed by Rabai for describing the dynamics of the two-substrate pH-oscillators was refined and shown that its appropriately formulated versions are suitable for the simulation of the dynamics both in the semi-batch and in the recently reported batch pH-oscillators as well.

Structured fibrous carbon-based catalysts for continuous nitrate removal from natural water

Bimetallic (Pd–Cu, Pd–Sn) nanoparticles supported on structured fibrous carbons (activated carbon fibers and carbon nanofibers grown on sintered metal fibers) were tested in nitrate removal of natural polluted water by hydrogen (a batch and continuous mode). Dependence of the activity/selectivity on catalyst chemical composition, promoter nature and metal particle size was studied. Sn-modified Pd nanoparticles showed higher N2 selectivity as compared to Cu-modified ones. The structured (Pd–Sn) nanoparticles supported on carbon nanofibers grown on Inconel sintered metal fibers demonstrated the best catalytic performance in an open flow reactor, providing optimal hydrodynamics properties.

Design of an efficient photocatalytic reactor for the decomposition of gaseous organic contaminants in air

Here, a strategy for decomposing gaseous organic contaminants by photocatalytic reactions is reported. A photocatalytic reactor is designed, based on an open tubular reactor with a UV light source installed at the center of the glass tube to permit the vertical irradiation of light onto the photocatalyst. TiO2 immobilized on a stainless steel plate and a fiber based material, respectively, are placed on the inner wall of an open tubular reactor. The fibers of felt induce wake and eddy flow near the inner surface of the reactor, resulting in compression of boundary layer. The compressed boundary layer provides a higher probability of contact between organic contaminants and the photocatalyst, consequently resulting in the enhanced photocatalytic oxidative decomposition of organic compounds. The inlet of photoreactor is modified in order to better control the bulk stream to form spiral-like flow. The reactor with a single tangent inlet exhibits the highest photocatalytic performance among the reactors examined, as an evidence of the improved probability of contact. Importantly, the reactor with a single tangent inlet, in which TiO2 immobilized felt is installed, maintains its photocatalytic activities for as long as twenty days.