Mass Transfer Limitations Research Articles

Carbon-based photoelectrochemical sensors: recent developments and future prospects.

Owing to the considerable potential of photoelectrochemical (PEC) sensors, they have gained significant attention in the analysis of biological, environmental, and food markers. However, the limited charge mass transfer efficiency and rapid recombination of electron hole pairs have become obstacles in the development of PEC sensors. In this case, considering the unique advantages of carbon-based materials, they can be used as photosensitizers, supporting materials and conductive substrates and coupled with semiconductors to prepare composite materials, solving the above problems. In addition, there are many types of carbon materials, which can have semiconductor properties and form heterojunctions after coupling with semiconductors, effectively promoting the separation of electron hole pairs. Herein, we aimed to provide a comprehensive analysis of reports on carbon-based PEC sensors by introducing their research and application status and discussing future development trends in this field. In particular, the types and performance improvement strategies of carbon-based electrodes and the working principles of carbon-based PEC sensors are explained. Furthermore, the applications of carbon-based photoelectric sensors in environmental monitoring, biomedicine, and food detection are highlighted. Finally, the current limitations in the research on carbon-based PEC sensors are emphasized and the need to enhance the sensitivity and selectivity through material modification, structural design, improved device performance, and other strategies are emphasized.

Nanoconfined tandem three-phase photocatalysis for highly selective CO2 reduction to ethanol.

The conversion of CO2 and H2O into ethanol with high selectivity via photocatalysis is greatly desired for effective CO2 resource utilization. However, the sluggish and challenging C-C coupling hinders this goal, with the behavior of *CO holding the key. Here, a nanoconfined and tandem three-phase reaction system is established to simultaneously enhance the *CO concentration and interaction time, achieving an outstanding ethanol selectively of 94.15%. This system utilizes a tandem catalyst comprising an Ag core and a hydrophobic Cu2O shell. The hydrophobic Cu2O shell acts as a CO2 reservoir, effectively overcoming the CO2 mass-transfer limitation, while the Ag core facilitates the conversion of CO2 to CO. Subsequently, CO undergoes continuous reduction within the nanoconfined mesoporous channels of Cu2O. The synergy of enhanced mass transfer, nanoconfinement, and tandem reaction leads to elevated *CO concentrations and prolonged interaction time within the Cu2O shell, significantly reducing the energy barrier for *CO-*CO coupling compared to the formation of *CHO from *CO, as determined by density functional theory calculations. Consequently, C-C coupling preferentially occurs over *CHO formation, producing excellent ethanol selectivity. These findings provide valuable insights into the efficient production of C2+ compounds.

Assessment of Reaction Kinetics for the Dehydrogenation of Perhydro-Dibenzyltoluene Using Mg- and Zn-Modified Pt/Al2O3 Catalysts

The catalysts utilized for the dehydrogenation of dibenzyltoluene-based liquid organic hydrogen carriers (LOHCs) remain crucial. The state-of-the-art catalyst for dehydrogenation of dibenzyltoluene-based LOHC still suffers from deactivation and by-product formation. This is crucial in terms of the efficiency of the industrial dehydrogenation plant for hydrogen production, cyclability as well as the cost of replacing the catalyst. The development of catalysts with optimum performance, minimum deactivation and low by-product formation is required to attain the full benefits of the LOHC technology. Therefore, in this study, the effect of Mg and Zn modification on Pt/Al2O3 catalyst is investigated for the catalytic dehydrogenation of perhydro-dibenzyltoluene (H18-DBT). In addition, an assessment of reaction kinetics is also conducted. High dehydrogenation performance was obtained for Mg-doped Pt/Al2O3 using a batch reactor at 300 °C and 6 h reaction time. In this case, the degree of dehydrogenation (dod), productivity and conversion obtained are 100%, 1.84 gH2/gPt/min and 99.9%, respectively. Moreover, the Mg-doped catalyst has resulted in a high turnover frequency (TOF) of 586 min−1 compared to the Zn-doped catalyst (269 min−1) and the undoped catalyst (202 min−1) at the reaction temperature of 300 °C. The amount of by-products increased with an increase in the catalytic activity, with the Pt/Mg-Al2O3 catalyst possessing the highest amount of by-products. The dehydrogenation of H18-DBT followed first-order reaction kinetics. In addition, the activation energy obtained using the Arrhenius model is 102, 130 and 151 kJ/mol for Pt/Al2O3, Pt/Zn-Al2O3 and Pt/Mg-Al2O3, respectively. Although the Mg-doped Pt/Al2O3 shows high activation energy, the higher performance of the catalyst suggests that mass transfer limitations have no major effect on the dehydrogenation reaction under the conditions used.

Post-Synthetic Ensembling Design of Hierarchically Ordered FAU-type Zeolite Frameworks for Vacuum Gas Oil Hydrocracking.

Zeolites hold importance as catalysts and membranes across numerous industrial processes that produce most of the world's fuels and chemicals. In zeolite catalysis, the rate of molecular diffusion inside the micropore channels defines the catalyst's longevity and selectivity, thereby influencing the catalytic efficiency. Decreasing the diffusion pathlengths of zeolites to the nanoscopic level by fabricating well-organized hierarchically porous architecture can efficiently overcome their intrinsic mass-transfer limitations without losing hydrothermal stability. We report a rational post-synthetic design for synthesizing hierarchically ordered FAU-type zeolites exhibiting 2D-hexagonal (P6mm) and 3D-cubic (Ia d) mesopore channels. The synthesis involves methodical incision of the parent zeolite into unit-cell level zeolitic fragments by in situ generated base and bulky surfactants. The micellar ensembles formed by these surfactant-zeolite interactions are subsequently reorganized into various ordered mesophases by tuning the micellar curvature with ion-specific interactions (Hofmeister effect). Unlike conventional crystallization, which offers poor control over mesophase formation due to kinetic constraints, crystalline mesostructures can be developed under dilute, mild alkaline conditions by controlled reassembly. The prepared zeolites with nanometric diffusion pathlengths have demonstrated excellent yields of naphtha and middle-distillates in vacuum gas oil hydrocracking with decreased coke deposition.

Mass transfer studies on the solvent-free lipase-catalyzed partial hydrolysis of palm oil in packed-bed reactor

Packed-bed reactor (PBR) is widely employed for enzyme-mediated reactions at an industrial scale because the reactor configuration enables reusability of the biocatalyst with ease, thereby reducing the overall operating expenses. However, mass transfer limitation remains a key challenge in fixed-bed column systems, especially at large scale. Therefore, the present study investigated the external mass transfer effects on solvent-free lipase-catalyzed partial hydrolysis reaction and aimed to develop a mass transfer model for the operation. The influence of volumetric flow rate, one of the crucial operating parameters affecting the external mass transfer resistance, was examined. Results demonstrated increasing the flow rate led to an increase in hydrolysis reaction with the highest reaction rate observed at 5 ml min-1 . A dimensionless mathematical mass transfer model of Colburn factor, JD = K(Re)n-1 which is a function of Reynolds and Schmidt numbers, was then proposed to simulate the enzymatic partial hydrolysis reaction of palm oil in PBR. The mass transfer model was analyzed with different n values and results revealed that the mass transfer correlation of JD=0.92(Re)-0.2 was able to predict the experimental data accurately. The model developed could describe the dominance of mass transfer effects besides providing useful information for the scale-up design of industrial reactor.

EXPERIMENTAL STUDY OF THE PRESSURE DROP AND FLOODING IN A ROTATING PACKED BED REACTOR

In conventional packed beds, mass transfer and flooding limitations lower the productivity of many processes. The almost zero sensitivity to variations in gravitational force has made centrifugal processes to have great potential for enhancing heterogeneous catalytic reactions. We studied a rotating packed bed (RPB) reactor as a gas/liquid contactor for multi-phase catalytic reactions. The scarcity of fundamental data on the hydrodynamics and mass transfer of the reactor limits the design, scale-up, and retrofitting of RPB reactors. Hence, we focused on the hydrodynamic behavior of the device. Previous studies on RPB reactor flooding and operating limits dwelled on visual observations and pressure drop variations only. However, physical visualizations are subjective because RPB reactor pressure drop variations are too inconsistent to be used to determine the upper operating limit during their operations. A robust quantitative method of obtaining RPB reactor flooding limits based on the flow rate of the ejected liquid, supported by visual observation and pressure drop measurement, was presented. The aim was to identify, with greater certainty, RPB reactor hydrodynamic characteristics and provide a more standard method of identifying it. The average increase in single-phase pressure drop per unit increase in rotation speed in the range investigated was 0.75Pa/rpm, and the average increase in pressure drop per unit increase in gas flow rate was 4.11Pa/Nm3h-1 within the operating range investigated.

Effect of surfactant addition on the biofiltration of siloxane-contaminated gas streams

Biogas contains low levels of volatile methyl siloxanes (VMS), which are responsible for severe damage to turbines or internal combustion engines during energy recovery. In this study, we investigated the removal of the linear octamethyltrisiloxane (L3) and cyclic octamethylcyclotetrasiloxane (D4) from gas by using two biofilters (BFs) filled with either woodchips and compost (WC) or perlite (PER). To overcome the mass transfer limitation, the addition of a synthetic (Tween 80) and a biological (Quillaja saponin, QS) surfactant on the removal of VMS in both BFs was studied. Tween 80 (added at × 1 critical micelle concentration, CMC) and QS (also at × 1 CMC) enhanced VMS removal in both BFs. Specifically, the performance of both BFs increased from an average VMS elimination capacity (EC) of 0.07 ± 0.04 g VMS m−3 h−1 to 0.24 ± 0.08 g VMS m−3 h−1 (Tween 80) and 0.43 ± 0.02 g VMS m−3 h−1 (QS). However, higher concentrations of Tween 80 ( × 3 CMC) did not further improve VMS removal. The WC BF exhibited a higher maximum EC of 0.63 g VMS m−3 h−1 (0.37 g D4 m−3 h−1 and 0.26 g L3 m−3 h−1), with a VMS RE of 28.4 ± 2.0% (D4 RE = 30.4% and L3 RE = 26.5%). The PER BF obtained a maximum EC of 0.52 g VMS m−3 h−1 (0.28 g D4 m−3 h−1 and 0.23 g L3 m−3 h−1), along with a VMS RE of 32.0 ± 0.8% (D4 RE = 31.2% and L3 RE = 32.8%). The most abundant genera in the WC BF were Mycobacterium (7.5–1.8%), Rhodococcus (1.1–7.2%), and Planctomicrobium (5.1–2.9%). However, given the high microbial diversity present in WC BF and the complex structure of VMS, their removal was most likely due to the joint activity of several microorganisms with VMS-degrading capacity, such as Bacillus (0.58–0.39%), Pseudomonas (0.07–0.04%), Dokdonella (0.50–0.10%), Microbacterium (0.5%), Novosphingobium (0.02%), Gordonia (0.5–0.1%), and Sphingopyxis (0.07%).

Electrocatalytic conversion of methane: Recent progress and future prospects

Methane has gained significant attention due to its abundant reserves and notable greenhouse effect. Electrocatalytic conversion of methane is an efficient and green pathway proceeding under mild conditions. However, the low solubility of methane in aqueous electrolytes imposes mass transfer limitations, leading to low current densities in electrocatalytic reactions and hindering large-scale production. This paper discusses the recent progress in quite a few aspects of electrocatalytic conversion of methane. Firstly, the reaction mechanisms involved in methane electrocatalysis are summarized, including dehydrogenation and C–H bond cleavage mediated by the active species. Next, we discuss how to promote electrochemical methane conversion regarding both the reaction process and mass transfer from the perspective of chemical engineering. Considerable efforts have been done to enhance the reaction process, including developing efficient electrocatalysts and devices. Meanwhile, the enhancement of transport processes via, e.g. improving the solubility of methane and modification on the transport area and distance, also facilitates more efficient methane conversion. Finally, an outlook on future development challenges is provided.

Plasma-Driven Synthesis of 3D Self-Supported Ni-Fe Nanostructures for Green Hydrogen Production

Hydrogen is considered as a future energy carrier due to its desirable characteristics such as high energy density, wide range of applications, and near-zero greenhouse gas emissions. Amongst the various hydrogen production methods, electrochemical water splitting is a promising alternative for producing large-scale green hydrogen. Recently, Anion Exchange Membrane Water Electrolysis (AEMWE) has garnered special attention due to its advantages such as use of low-cost materials and higher performance over conventional techniques such as Alkaline Water Electrolysis (AWE) or Proton Exchange Membrane Water Electrolysis (PEMWE).In the development of anodic electrodes for AEMWE, nickel-based materials have been extensively studied as promising low-cost substitutes to expensive noble metal catalysts such as IrO2 and RuO2. To improve the catalytic performance, interfacial engineering, intercalation, nanostructuring techniques are commonly used1. The nanostructured catalysts are typically synthesized in powder form, which then requires a binder to coat them on a substrate. The extra interfaces between the catalyst, substrate and the electrolyte can cause charge and mass transfer limitations as well as restrict the availability of active sites2. Under gas evolution conditions, it can also lead to mechanical shedding and delamination of catalysts. This limits the applicability of emerging electrocatalysts on a commercial scale, thus making it essential to explore novel fabrication routes for synthesizing self-supported nanostructures.Helium plasma irradiation is a potential alternative wherein the nanostructures are created on the substrate itself, and thus can potentially alleviate some of the shortcomings of conventional methods. The plasma irradiation technique has been extensively studied in relation to the surface erosion and embrittlement of fusion reactors3,4. However, its application has been limited mostly to planar surfaces and only a few studies have employed this technique in solar-to-hydrogen production5,6. Herein, we report plasma-driven synthesis of nanostructured 3D electrodes and their integration in a membrane electrode assembly (MEA).The MEA with self-supported nanostructures delivers ≈25% higher performance than its bare counterpart at room temperature. Additionally, iron incorporation further increases the performance, surpassing commercially available NiFe electrocatalysts. Going forward, the durability and performance of the self-supported electrodes at higher temperatures will be explored and the applicability of this technique to other renewable energy systems is expected to be correlated.

Fast Estimation of Entropy Profiles for Lithium-Ion Batteries

The operating temperature of a lithium-ion battery (LIB) has strong effects on its electrochemical performance, safety, and lifetime. Reliable predictions of cell temperature and heat generation are required for the design and thermal management of battery systems. During the normal operation of LIBs, heat sources can be classified into irreversible heat from resistive losses such as ohmic resistance, charge-transfer overpotentials, and mass-transfer limitations; and reversible heat from entropy change . The irreversible heat generation is related to the cell's internal resistance and the applied current. The reversible heat depends on the entropy variation of electrode materials, the state of charge (SoC), and the temperature. An accurate measurement of entropy-variation will not only help to improve the battery operation under optimal thermal conditions but can also be used to diagnose the battery aging since it can reveal crystal structure changes in the electrodes [1, 2].Techniques for measuring the entropy of a battery can mainly be classified into potentiometric [3] and calorimetric methods. The potentiometric method measures the open circuit voltage (OCV) changes while the cell temperature is varied at different SoCs. This method requires a long relaxation time to obtain the OCV equilibrium state following each SoC point and temperature step. The calorimetric method [4-6] is based on measuring the heat generation during charge and discharge, and various models are applied to differentiate between and quantify the reversible and irreversible heat sources. The entropy variation with SOC is obtained via the reversible heat rate.Recent improved methods include e.g., Schmidt et al. [4] who proposed a reversible heat extraction method based on electrothermal impedance spectroscopy (ETIS) and Damay et al. [5] proposing a fast calorimetric method to obtain a continuous entropy profile. The cell surface temperature is monitored while the battery is charged and discharged continuously. A thermal balance is used to estimate the heat generation from the monitored cell temperature changes during charge and discharge. The benefit of this method can be low cost, fast and high resolution. Bedürftig et al. [6] proposed a calorimetric method named ‘Double Pulse Method’ to measure reversible heat in lithium-ion battery cells by exciting the cell with charge and discharge current pulses.Here we present a new entropy characterization method via charge and discharge cycles of a LIB at low constant C-rates using simple insulating condition. Through monitoring the variations of cell surface temperature and voltage with the state of charge, the continuous variation of entropy with the state of charge can be extracted. These results were compared to classical entropy measurements obtained through the potentiometric method as shown in Figure 1. In addition, the extracted entropy variation data is input into a LIB modelling approach, combining a P2D-electrochemical sub-model for battery operation and a 3D-finite-element sub-model for thermal behavior while battery charge and discharge. The model predictions on the cell outer surface temperature variation while charge and discharge under different C-rates are compared with the data obtained in the battery characterization tests as shown in Figure 2. Good agreements between the model predictions and tests are achieved.

(Invited) Non-Uniformly Polarized Reactive Electrochemical Membrane (REM) for Water Purification

A novel flow-through electrochemical technology (or termed reactive electrochemical membrane, REM) developed from porous electrode materials has recently attracted increasing attention globally in water purification and environment remediation. REM systems compress the boundary diffusion layer on the surface of the electrode via a combination of the convection of the solution and the constraint effect of the micro-pore structure, thus overcoming the mass transfer limitation in traditional flow-by systems. As a result, the kinetics of contaminant separation and conversion in a REM system increases by several to tens of times as compared with the flow-by systems. However, most existing studies are focused on the development of novel electrode materials, the evaluation of the removal efficiency and mechanism for contaminants, and the optimization of the treatment process of a REM system. In comparison, there is a gap in understanding the working principles of the REM electrodes. In contrast to the traditional flow-by system, the convective transport of the solution in the REM system drives the contaminants to the inside of the REM electrode, which activates the inner catalytic zone thereby. Because the electrode features the characteristics of non-uniform polarization, the given potential decays continuously along the depth of the REM electrode, thus causing a non-uniform distribution of the potential inside the REM electrode. As such, the zero-dimensional reaction theory of the electrode in traditional flow-by system (that is, the reaction mainly occurs on the surface of the electrode and is controlled by the potential) is no longer applicable to REM electrodes. It is therefore vital to revisit the reaction mechanism of the REM electrode. This Presentation therefore discusses the non-uniform polarization characteristics of the REM electrodes that are developed by loading catalytic layer on porous substrates. The main contents include: (1) REM electrode d emonstrates non-uniform oxidation characteristics: The key influencing factors ( i.e. , the pore structure of the REM electrode and the concentration of the electrolyte) and their principles of action to determine the reaction depth of a REM electrode have been identified, by employing (1) a developed mathematical model that could describe the spatial overpotential distribution as a function of depth in the REM electrode and (2) a visualization method to characterize the reactive depth of a REM electrode. (2) There is a structure-function relationship between the REM electrode pore structure and water purification efficiency : A series of SnO2-Sb-REMs with pore diameters in a range of 4.7 to 49.4 μm have been prepared to study the influence of the key factor ( i.e. , pore structure) on the transport-oxidation process of typical antibiotics. The REM electrode performance that could not constantly increase with a decrease in the pore diameter relates to the decreasing reactive depth of the electrode at a smaller pore diameter, which would lead to the compromise of the intrinsic kinetics of a REM electrode. (3) Direct electron transfer (DET) dominates the oxidation of antibiotics by using REM developed from porous substrates with a catalytic layer: The mechanism of typical antibiotics removal by employing SnO2-Sb-REM, β -PbO2-Sb-REM and Ti4O7-REM has been systematically investigated. The non-uniform oxidation characteristics of the REM electrode resulted in the DET rate being much higher than the yield of the hydroxyl radical (•OH), which was insignificantly affected by the electrode materials. The strong DET ability enabled the REM system to quickly and efficiently degrade antibiotics, which also imparted the REM system a stronger resistance to the background matrix (such as Cl–, HCO3 – and natural soluble organic matter).

Optimization of an Open-Cell Foam-Based Ni-Mg-Al Catalyst for Enhanced CO2 Hydrogenation to Methane

In the presented work, the catalytic performance of a nickel catalyst, in CO2 hydrogenation to methane, within a ZrO2 open-cell foam (OCF)-based catalyst was studied. Two series of analogous samples were prepared and coated with 100–150 mg of a Mg-Al oxide interface to stabilize the formation of well-dispersed Ni crystallites, with 10–15 wt% of nickel as an active phase, based on 30 ppi foam or 45 ppi foam. The main factor influencing catalytic performance was the geometric parameters of the applied foams. The series of catalysts based on 30 ppi OCF showed CO2 conversion in the range of 30–50% at 300 °C, while those based on 45 ppi OCF resulted in a significantly enhancement of the catalytic activity: 90–92% CO2 conversion under the same experimental conditions. Calculations of the internal and external mass transfer limitations were performed. The observed difference in the catalytic activity was primarily related to the radial transport inside the pores, confirmed with the explicitly higher conversions.

Challenges and prospects of microbial α-amylases for industrial application: a review.

α-Amylases are essential biocatalysts representing a billion-dollar market with significant long-term global demand. They have varied applications ranging from detergent, textile, and food sectors such as bakery to, more recently, biofuel industries. Microbial α-amylases have distinct advantages over their plant and animal counterparts owing to generally good activities and better stability at temperature and pH extremes. With the scope of applications expanding, the need for new and improved α-amylases is ever-growing. However, scaling up microbial α-amylase technology from the laboratory to industry for practical applications is impeded by several issues, ranging from mass transfer limitations, low enzyme yields, and energy-intensive product recovery that adds to high production costs. This review highlights the major challenges and prospects for the production of microbial α-amylases, considering the various avenues of industrial bioprocessing such as culture-independent approaches, nutrient optimization, bioreactor operations with design improvements, and product down-streaming approaches towards developing efficient α-amylases with high activity and recyclability. Since the sequence and structure of the enzyme play a crucial role in modulating its functional properties, we have also tried to analyze the structural composition of microbial α-amylase as a guide to its thermodynamic properties to identify the areas that can be targeted for enhancing the catalytic activity and thermostability of the enzyme through varied immobilization or selective enzyme engineering approaches. Also, the utilization of inexpensive and renewable substrates for enzyme production to isolate α-amylases with non-conventional applications has been briefly discussed.

Identification of Mass Transfer Limitations by Kinetic Modeling of a Technical-Scale Trickle Bed Reactor for the Hydrogenation of Viscous Aromatics

Identification of Mass Transfer Limitations by Kinetic Modeling of a Technical-Scale Trickle Bed Reactor for the Hydrogenation of Viscous Aromatics

Reduced graphene oxide membrane confined bimetallic organic framework boosts Fenton-like process to ultrafast contaminants degradation

Fenton-like processes generate reactive oxygen species (ROS) to achieve degradation of organic pollutants, however, practical water treatment processes suffer from low ROS utilization owing to its ultra-short lifetime and mass transfer limitations. To solve these problems, a nano-confined reaction space was designed to facilitate a fast mass transfer process for efficient removal of organic pollutants. Herein, the CuCo-based bimetallic organic framework (CuCo-MOF) was loaded in the water-transporting interlayer nanochannels of reduced graphene oxide (rGO) membrane. Membrane-confined CuCo-MOF with multiple exposed reaction sites activate peroxymonosulfate (PMS), generating ROS for ultrafast removal of oxytetracycline (OTC) at a water fluxes of 87.3 L·m−2·h−1. Notably, this membrane can continuously and stably degrade OTC (100 %) within 30 h. In addition, free radical capture experiments and EPR analysis indicated that the main ROS of the reaction system were singlet oxygen (1O2) and sulfate radical (SO4−). Based on Fukui index results and LC-MS analysis, reaction sites of OTC attacked by ROS were identified and it’s possible degradation pathways were proposed.

Regulation of Sulfur Atoms in MoSx by Magneto-Electrodeposition for Hydrogen Evolution Reaction.

Compared with crystalline molybdenum sulfide (MoS2) employed as an efficient hydrogen evolution reaction (HER) catalyst, amorphous MoSx exhibits better activity. To synthesize amorphous MoSx, electrodeposition serving as a convenient and time-saving method is successfully applied. However, the loading mass is hindered by limited mass transfer efficiency and the available active sites require further improvement. Herein, magneto-electrodeposition is developed to synthesize MoSx with magnetic fields up to 9 T to investigate the effects of a magnetic field in the electrodeposition processing, as well as the induced electrochemical performance. Owing to the magneto-hydrodynamic effect, the loading mass of MoSx is obviously increased, and the terminal S2- serving as the active site is enhanced. The optimized MoSx catalyst delivers outstanding HER performance, achieving an overpotential of 50mV at a current density of 10mA cm-2 and the corresponding Tafel slope of 59mV dec-1. The introduction of a magnetic field during the electrodeposition process will provide a novel route to prepare amorphous MoSx with improved electrochemical performance.

Control of selectivity in the oxidation of 5-hydroxymethylfurfural to 5- formyl-2-furancarboxylic acid catalyzed by laccase in a multiphasic gas-liquid microbioreactor

The selectivity of 5-formyl-2-furancarboxylic acid (FFCA) was studied in a batch bioreactor and microbioreactors with different internal diameters (ID). Using microbioreactors, the effect of the flow rate of the liquid and gas phase on the yield, space time yield (STYFFCA), and gas–liquid mixture velocity (UM) of the reaction was evaluated. The biooxidation in flow microbioreactors, a selectivity of 100 % for FFCA was achieved, while with the batch bioreactor at the same substrate concentration a selectivity of 6.7 % was obtained. The highest yield (30 %) with 15 mM of 5-hydroxymethylfurfural (HMF) was reached at a gas–liquid flow rate of 0.5 µL/min and the highest STYFFCA (0.07 mol m−3 min−1) was achieved at a gas–liquid flow rate of 1.5 µL/min with the microbioreactor with an ID of 0.5 mm. The UM values (0.5 to 1.6 cm min1) indicated that the reaction takes place under a kinetic regime without mass transfer limitations.

Kinetics and Dynamics of Sorption of the Glucose Target Molecule by a Molecularly Imprinted Polymer

The effect of imprinting of a polymer matrix based on ethylene glycol dimethacrylate on the kinetics and dynamics of binding of the glucose target molecule has been studied. The contribution of the adsorption act to the sorption kinetics of the target sorbate by the molecularly imprinted polymer was established. Mixed-diffusion limitation of mass transfer and cooperative adsorption of glucose molecules during sorption by both imprinted and nonimprinted polymer granules were revealed. The binding rate and accessibility of sorption sites in the imprinted polymer were shown to increase, and frontal sorption occurred in a regular mode.

A review of autotrophic denitrification for groundwater remediation: A special focus on bioelectrochemical reactors

Groundwater is an important resource that can help in climate change adaptation. However, the pollution of these aquifers with nitrate is a widespread problem of growing concern. Biological denitrification using inorganic electron donors shows significant advantages in treating nitrate-polluted groundwater where organic matter presence is negligible. However, mass transfer limitations and secondary contamination seem to be the major hinderance to spread the use of these technologies. This could be solved by the use of bioelectrochemical systems (BES), which emerge as an attractive technology to solve these problems due to the reported low energy demand and high denitrification rates. However, technical and operational issues must be considered to replicate these results at full-scale. This review summarizes the biological basis of autotrophic denitrification and the key aspects of its application in bioelectrochemical systems. In addition, an estimation of the capital costs required for the implementation of a BES considering different population sizes and initial nitrate concentration in the groundwater is made.

Spatial confinement of Co-N-C catalyst in carbon nanocuboid for water Decontamination: High Performance, mechanism and biotoxicity assessment

Encapsulating free radical species with super-short lifetime and organic pollutants inside the chemical theoretical diffusion length scale by spatial confinement could offer a strategy with great promise to resolve the mass transfer restrictions in heterogeneous Fenton-like systems. Herein, we reported the spatial confinement of Co, N co-doped carbon (Co-N-C) catalyst in carbon nanocuboids (Co-CNCs), via encapsulation of Co-N-C catalyst into CNCs, for activating CaSO3 to efficiently degrade sulfamethoxazole. The detailed characterizations confirmed ZIF-9 was successfully transformed into N-doped carbon nanocuboids at 850 °C calcination. Co-N-C catalyst was successfully confined into carbon nanocuboids, is beneficial to prevent the aggregation of Co nanoparticles, thereby facilitating its stability and catalyst activity in sulfamethoxazole (SMX) removal via CaSO3 activation. Compared with other sulfites (including Na2SO3 and NaHSO3), CaSO3 (82%) presented much higher degradation efficiency than those of NaSO3 (18%) and NaHSO3 (41%) in SMX removal, emphasizing the critical role of CaSO3 in water decontamination. Because CaSO3 could discharge SO32- persistently and slowly, preventing from the consumption of the formed SO4•- at a high concentration of aqueous SO32-. Quenching test and mechanism study had verified that •OH and SO4•- (SO3•-) were the major reactive species in Co-CNC-850/CaSO3 system. In addition, Zebrafish toxicology assays and seed germination experiments had revealed the biotoxicity of SMX to zebrafish and wheat seeds was significantly reduced after degradation via Co-CNC-850/CaSO3 system.