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•The ZnO/PPy composite showed to produce OH radicals under visible light.•The evaluation of mass transfer showed that the degradation of AV7 was kinetically controlled.•The adsorbed ...AV7 molecule presents mobility and reacts with OH radicals formed on surface.
In this work, a composite of ZnO and polypyrrole (ZnO/PPy) was synthesized by polymerization method and characterized by X-ray diffraction (XRD), Ultraviolet–Visible with Near-infrared (UV–Vis NIR) spectroscopy and Fourier Transform Infrared (FT-IR) spectroscopy, both by diffuse reflectance mode. The ZnO/PPy composite was tested as photocatalyst for the degradation of acid violet 7 dye under visible light radiation in two systems: a) by using a batch reactor and b) in a continuous annular reactor. The hole formation in the valence band was evidenced using a hole scavenger test for ZnO/PPy composite and also the hydroxyl radicals formation capacity was determined. A three-resistance model of mass transfer (MT) was evaluated, it considers the traditional external mass transfer coefficient (She) to obtain an overall mass transfer coefficient (Shapp), the model is considered a full 3-D convection–diffusion–reaction applied to the photocatalyst of ZnO/PPy composite attached onto the interior wall of a quartz ring (annular space). The MT analysis showed in the continuous reactor that the degradation reaction was kinetically controlled. A Langmuir-Hinshelwood (L-H) model was analyzed according the fitting of the experimental data in the annular continuous photocatalytic reactor. The adsorption parameter obtained with L-H model was validated based on thermodynamic criteria for the changes in the standard enthalpy of adsorption (ΔHadso) and standard total entropy of adsorption (ΔSadso). The analysis of thermodynamic properties revealed that the adsorbed AV7 molecule on ZnO/PPy photocatalyst still presents mobility in order to react to the very short time OH radicals formed on surface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this paper the authors review 25 original Small and Medium sized Reactor designs currently under development, licensing procedure or in operation. Technology overview, safety features and ability ...to mitigate proliferation are considered. In order to show common research trends and highlight the features of particular designs the authors choose to classify the reactors according to used technology and cooling medium. The main requirement for a new reactor design is to secure inherent and passive safety features, thus different ways to achieve it are shown. The Pressurized Water Reactor (PWR) is the most advanced and most commonly used technology. In PWR, passiveness and inherency of safety features are ensured by integrating steam generators inside the Reactor Pressure Vessel (RPV). It eliminates possibility of Loss of Cooling Accident (LOCA); moreover the technology allows swift removal of heat produced during normal or accidental conditions. Heavy Water Reactors (HWRs) are also in operation, however, the design process of improving emergency cooling system is ongoing. The design of Supercritical Water Reactor (SCWR) based on Canadian HWR is reviewed including the ongoing development in novel leakage detection method and material improvement. Liquid Metal Cooled Reactors (LMCR) are in advanced stage of research and development focusing on lead and sodium as the coolants. LMCR are secured from LOCA accidents due to low operating pressure and integration of the most elements in RPV. In case of Advanced Gas-Cooled Reactors (AGCR) the literature indicates several possible system integrations related to high operating temperature under development. AGCRs are able to use fully passive systems during all events due to their low power density. Furthermore, it is noted that the use of innovative reactor designs can mitigate proliferation concerns to an acceptable level. The authors identify the common research trend among all designs as the fuel cycle evaluation and optimization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The development of green synthetic approaches is one of the key materials challenges in moving toward semiconductor quantum dots (QDs) for large-scale production and commercial applications. This ...article presents a comprehensive overview on the synthesis of colloidal QDs prepared via chemical approaches in solution phase, with emphasis on green routes which possess the advantages of environment-friendly raw materials, simple operation process, and robust mass-scale production. The approaches for the synthesis of QDs in batch reactors are summarized, including hot-injection organometallic synthesis, noninjection organometallic synthesis, aqueous synthesis and biosynthesis approaches, with some of the concerns on their limitations for scale-up, followed by some continuous synthetic methods aiming for reproducible and large-scale production. Current advances in continuous synthesis of QDs by microfluidic devices, high-gravity reactors, and spray-based techniques are briefly introduced. We also provide some insights into challenges and opportunities based on our own understanding of this field.
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•Different admixtures of three popular photocatalysts were immobilized in a polystyrene film.•A novel airlift reactor incorporating the film was fabricated and tested for dye ...removal.•A synergistic effect among the three photocatalysts in the film was observed.•The airlift photocatalytic reactor is quite efficient and effective.•The prepared film can be reused effectively many times.
Reduced graphene oxide (rGO) as well as graphitic carbon nitride (g-C3N4) catalysts were synthesized and a physical admixture of rGO and g-C3N4 along with TiO2 in the ratio of 1:1:1 by weight was immobilized in a polystyrene film using the facile solvent casting method. An internal loop airlift reactor with a working volume of 1.2 litres incorporating the prepared polymer-based photocatalytic film was designed and tested for the photocatalytic degradation of remazol turquoise blue dye synthetic wastewater. The reactor parameters affecting the photocatalytic activity such as airflow rate and Di/Do (ratio of draft tube diameter to outer tube diameter) were evaluated. The successful operation of the reactor obtained using the ternary immobilized catalyst mixture film gave 92.25% total organic carbon reduction and 94% decolourization within 140 min, compared to 91% decolourization by the slurry form within 40 min. Complete and quicker decolourization of the dye was also demonstrated under the influence of O3 or H2O2. The immobilized catalyst was successfully reused four times. The ternary catalyst admixture employed in this work and the unique design of the photocatalytic reactor helps to increase the degradation rate of toxic textile effluents thus making it suitable for larger scales of treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•A procedure for transforming a non-isothermal SBR process into a tubular reactor one is proposed.•The tubular reactor involves both a variable side feed and a variable heat ...exchange.•The proposed methodology does not require any kinetic information.•The syntheses of a copolymer is investigated as a case study.
Focusing on tubular reactors with continuously distributed side injections, a general procedure to evaluate the operating mode able to reproduce the performance of a given semi-batch reactor is worked out. Namely, such operating mode is expressed as axial profiles of feed flowrate and temperature of the cooling/heating medium inside the reactor jacket. This transformation procedure, previously limited to isothermal reactors, is extended here to non-isothermal systems. The process performance (selectivity and conversion) of the original discontinuous reactor are fully reproduced using the continuous intensified reactor, while its productivity remains a degree of freedom. Notably, like in the isothermal case, the transformation procedure is kinetics-free, i.e. the knowledge of the reaction kinetics is not a precondition.
As case study, a copolymerisation reaction is considered to demonstrate the potential of the method. Even though any SBR feed policy could be considered when applying this methodology, the optimal feed policy of the semi-batch reactor evaluated according to the so-called “power feed” procedure is examined considering the reactor non-isothermal. Afterwards, the proposed transformation method is applied and the performance of the two systems, discontinuous and continuous, are comparatively evaluated. Finally, given the practical difficulties associated with continuously distributed side injections, a discretisation approach is proposed based on the use of discrete lateral feeds and more realistic reactor configurations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Supercritical water gasification of glycerol and glucose for hydrogen-rich gas was conducted in two different reactors including quartz reactor and tubular reactor. The quartz reactors were batch ...reactors and they were made of SiO2 while the tubular reactor was a continuous reactor and the reactor was made of Hastelloy C-276. The feedstocks in quartz reactors were gasified at two different conditions (without nickel wire in the reactors and with nickel wire in the reactors). The carbon gasification efficiency (CGE) of glycerol and glucose in quartz reactors with nickel wire were higher than that without nickel wire. The feedstocks gasified in tubular reactor were also promoted by the catalytic effects of the reactor wall. The CGE of glycerol and glucose in the tubular reactor decreased with time because the reactor wall was covered by char generated from these feedstocks and the catalytic active of wall reduced with time. Analysis of the gasification results in these two reactors shows that the catalytic wall played an important role in supercritical water gasification and significantly improved the gasification efficiency.
•The percentage of H2 in gas improved markedly with nickel wire in the quartz reactor.•Char attached to the reactor wall led to the decrease of the catalytic activity of wall.•The catalytic reactor wall could greatly promote the water-gas shift reaction, methanation reaction and CC bond breaking.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Over the past two decades, the pharmaceutical and specialty chemical industries have led a considerable effort toward transitioning from existing batch to continuous flow processes. The transition ...promises many benefits, including improved automation, simpler scale-up, and higher throughput. The switch from batch reactor vessels to continuous flow reactors (CFRs) is among the most challenging problems that must be solved to succeed in making the batch to continuous process switch, and the best methodology by which the feasibility of the switch can be determined remains an open problem. In this work, we offer a novel, optimization-based framework for assessing the feasibility of the switch. Starting from first principles, we develop a general nondimensionalization algorithm for describing an arbitrary reactive system. We then define nondimensional performance metrics that allow us to assign “scores” for a given batch reactor or CFR. Finally, we construct two optimization problems that (1) minimize the difference in total performance between an existing batch reactor and a potential new CFR and (2) separately maximize the total performance of the two reactors. The design variables for each reactor are allowed to vary between realistic bounds for the particular reactor vessel type. Problem 1 provides insight into whether the switch is feasible, while problem 2 provides insight into whether the switch is desirable. Finally, we illustrate the utility of our framework using two case studies.
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•A successful method for the immobilization of redox mediator is proposed.•Functionalized activated carbon improves azo dye reduction in batch and continuous.•Simultaneous treatment of two ...recalcitrant pollutants in UASB reactor.•The longest operation in continuous reactor using immobilized redox mediator.
In this research was immobilized anthraquinone-2-sulfonate (AQS) on granular activated carbon (GAC) to evaluate its capacity to reduce congo red (CR) in batch reactor and continuous UASB reactors. The removal of p-cresol coupled to the reduction of CR was also evaluated. Results show that the immobilization of AQS on GAC (GAC-AQS) achieved 0.469mmol/g, improving 2.85-times the electron-transferring capacity compared to unmodified GAC. In batch, incubations with GAC-AQS achieved a rate of decolorization of 2.64-fold higher than the observed with GAC. Decolorization efficiencies in UASB reactor with GAC-AQS were 83.9, 82, and 79.9% for periods I, II, and III; these values were 14.9–22.8% higher than the obtained by reactor with unmodified GAC using glucose as energy source. In the fourth period, glucose and p-cresol were simultaneously fed, increasing the decolorization efficiency to 87% for GAC-AQS and 72% for GAC. Finally, reactors efficiency decreased when p-cresol was the only energy source, but systems gradually recovered the decolorization efficiency up to 84% (GAC-AQS) and 71% (GAC) after 250 d. This study demonstrates the longest and efficient continuous UASB reactor operation for the reduction of electron-accepting contaminant in presence of quinone-functionalized GAC, but also using a recalcitrant pollutant as electron donor.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The effect of pretreatments by hydrothermolysis (180 °C; 15 min) and alkaline delignification (NaOH 5M; H2O2 1%; 24 h) in citrus peel waste (CPW) was evaluated, as well as the effect on H2, organic ...acids and alcohols production, in addition to characterization of the microbial community involved in fermentation. Batch reactors at 37 °C were operated with 3 gTVS/L of CPW with allochthonous consortium (UASB reactor sludge; 2 gTVS/L) and autochthonous of CPW (1.5 gTVS/L) as inocula. H2 production was higher in reactors with in natura CPW (13.31 mmol/L) compared to hydrothermolysis (8.19 mmol/L) and alkaline delignification (7.27 mmol/L). The acetogenic pathway was predominant in the in natura CPW (4,355 mg/L acetic acid). The most abundant genera in the in natura CPW and after hydrothermolysis were Clostridium (18.97 and 12.90%, respectively) and Ruminiclostridium (16.65 and 1.04%, respectively) commonly related to cellulolytic bacteria and/or H2 production.
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•CPW delignification was higher in hydrothermolysis than in alkaline pretreatment.•Lower limonene content in CPW after hydrothermolysis and alkaline delignification.•Effect of hydrothermolysis on the microbial community involved in CPW fermentation.•Clostridium as the most abundant genera evolved in CPW anaerobic digestion.•Acetic acid was the major organic acid obtained through CPW biodegradation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•BGCL process was investigated experimentally in batch and continuous reactor.•Natural hematite as oxygen carrier promoted biomass gasification in BGCL.•The experimental results were compared in ...batch and continuous reactor.•Phase analyzing for hematite was investigated in batch and continuous reactor.
Biomass gasification using chemical looping (BGCL) is an innovative biomass gasification technique using lattice oxygen from oxygen carrier. The present work selected natural hematite as oxygen carrier, and experimental results from batch reactor and continuous reactor were compared in this work. The results showed that the presence of hematite would accelerate the process of biomass gasification and enhance carbon conversion rate, and hematite could increase the heat-carrier capacity of bed materials in the continuous reactor. In the batch reactor, carbon conversion efficiency and fraction of CO+H2 increased within the temperature range of 750–900°C. However, syngas yield in the continuous reactor reached the maximum of 0.64Nm3kg−1 at 850°C. Besides, the effect of hematite fraction on the gasification performance was similar between the batch reactor and the continuous reactor. When hematite fraction was exceed 40wt.%, higher hematite fraction resulted in higher carbon conversion efficiency and lower syngas production. At last, the phase characterization of reduced hematite was investigated. Fe3O4 were the main reduced phases of hematite in the batch reactor, while FeO might be existed in the continuous reactor.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
