Liquid Contact Research Articles

3D‐Printed Hydrogel Filter for Biocatalytic CO2 Capture

AbstractInnovative scalable CO2 capture technologies are urgently needed to combat the climate crisis. Reactive absorption in alkaline liquids, an essential process for capturing CO2 at atmospheric pressure, requires high gas–liquid contact and fast reaction kinetics. To meet these needs, self‐supporting hydrogel CO2 gas–liquid contactors (or simply “CO2 filters”) containing the CO2 selective catalyst carbonic anhydrase (CA) are developed using the direct ink writing additive manufacturing approach. The multifunctional filters are composed of semi‐interpenetrating polymer network hydrogels (IPNHs) of poly (ethylene glycol) diacrylate/poly (ethylene oxide) (PEG‐DA/PEO) upon photocuring during 3D printing. Formulations with PEG‐DA levels of 30–60 wt% are sufficiently homogeneous and reactive to produce coherent grids. Based on operational parameters, a 56 wt% PEG‐DA formulation is selected to continuously print self‐supporting 3D stacked cylindrical grids, with or without enzymes in ink. The resulting enzyme‐laden IPHN filters deliver ≈3 times higher CO2 capture efficiency than the no‐enzyme control filters in a laboratory‐scale absorption column test. However, the enhancement effect decreases significantly within 2 d of operation, likely due to burst release of enzymes caused by the flowing solution. Covalent crosslinking of CA near the surface, which can improve durability and CO2 capture performance, will be evaluated in future studies.

Hydrophobic C60-modified PVDF membrane with micro-nano structures for mitigating CaSO4 scaling in direct contact membrane distillation (DCMD)

Membrane scaling is a non-negligible problem for membrane distillation (MD) in the treatment of high-salinity wastewater (e.g., calcium sulfate and calcium carbonate). In this study, fullerene (C60) was adhered to a polyvinylidene fluoride (PVDF) membrane using a polydimethylsiloxane (PDMS) solution to create a micro-nano structure, fabricating the C60/PDMS-PVDF membrane. This membrane was then re-immersed in a PDMS solution to further reinforce the C60 nanoparticles on the surface, forming the PDMS/C60/PDMS-PVDF membrane. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the membrane surface morphology. Fourier transform infrared (FT-IR) was used to explore the membrane chemical composition. Liquid entry pressure (LEP) and water contact angle (WCA) measurements were employed to assess the membrane wettability. The results showed that C60-modification created the micro-nano structure on the membrane surface. The WCA of the PVDF membrane was 112.7 ± 2.4°, with a sliding angle far greater than 90°, whereas the PDMS/C60/PDMS-PVDF membrane exhibited a WCA of 147.9 ± 3.2° and a sliding angle of 6.3°. Compared to the virgin PVDF membrane, the LEP value of the PDMS/C60/PDMS-PVDF membrane increased from 68.4 ± 2.7 kPa to 87.2 ± 3.3 kPa. In direct contact membrane distillation (DCMD), a CaSO4 solution (2 g/L) was used to test the membrane performance. After 48 hours of operation, the flux of the PDMS/C60/PDMS-PVDF membrane remained at approximately 3.57 kg/(m2·h), and the salt rejection rate was over 99.96 %. This could be attributed to the C60 modification forming a micro-nano structure on the membrane surface, which trapped an air layer. This air layer could reduce the contact area between the crystal and the membrane, decrease nucleation probability, and shorten the residence time of liquid on the membrane surface. Additionally, the PDMS/C60/PDMS-PVDF membrane exhibited superior stability during the ultrasonic destruction experiment due to the encapsulation of PDMS. In summary, a novel hydrophobic membrane with a micro-nano structure was fabricated through C60 modification, offering superior anti-scaling properties and stability in treating high-salinity wastewater.

A separation column for liquid mixture based on phase transform: Experiment and simulation

The concentric internally heat-integrated distillation column (HIDiC) has advantages of low energy consumption and high thermodynamic efficiency. However, its drawbacks of limited heat transfer area, complex internal structure, and large number of control parameters hinder its widespread industrial applications. To solve these challenges, in this work a novel sleeve-like concentric heat integrated separation column, namely temperature-controlled phase change column (TCPC), was developed to separate liquid mixtures in a more effective and energy-saving way with reflux section being moved and trays being replaced with spiral corrugation blades. The comprehensive performances of TCPC in ethanol–water system was firstly evaluated by experiments. The results showed that TCPC performs well in ethanol/water separation due to the internal spiral corrugation significantly reducing the vapor–liquid contact in separation section. Meanwhile, compared to the concentric HIDiC, TCPC has a higher total heat transfer coefficient due to the larger heat transfer area. Computational fluid dynamics simulation reveals the internal design of TCPC inducing secondary vortices of the vapor, enhancing condensation heat transfer and separation efficiency. Further, increasing mass flow rate within a certain range would enhance the comprehensive performance factor and lead to more effective separation.

An analytical treatment to spatially inhomogeneous population balance model

In modern liquid–liquid contact components, there is an increasing use of droplet population balance models. These components include differential and completely mixed contractors. These models aim to explain the complex hydrodynamic processes occurring in the dispersion phase. The hydrodynamics of these interacting dispersions include droplet breaking, coalescence, axial dispersion, and both entry and exit events. The resulting equations for population balance are represented as integro-partial differential equations, which rarely have analytical solutions, especially when spatial dependency is apparent. Consequently, the pursuit predominantly lies in seeking numerical solutions to resolve these complex equations. In this study, we have devised analytical solutions for inhomogeneous breakage and coagulation by employing the population balance equation (PBEs) applicable to both batch and continuous flow systems. The innovative approaches for solving PBEs in these systems leverage the Adomian decomposition method (ADM) and the homotopy analysis method (HAM). These semi-analytical methodologies effectively tackle the significant challenges related to numerical discretization and stability, which have often plagued previous solutions of the homogeneous PBEs. Our findings across all test examples demonstrate that the approximated particle size distributions utilizing these two methods converge to the analytical solutions continuously.

Recent Studies on Solid–Liquid Contact Electrification

Recent Studies on Solid–Liquid Contact Electrification

Response Time Dynamics of a Membrane-Based Microfluidic Gas Sensor

Practical gas–liquid interfacing is paramount in microfluidic technology, particularly in developing microfluidic gas sensors. We have created an easily replicable membrane-based closed microfluidic platform (MB-MP) to achieve in situ gas–liquid contact for low-resource settings. We have fabricated the MB-MP using readily available materials like double-sided tape or parafilm without conventional soft lithographic techniques. The response characteristics of the MB-MP are studied using CO2 as the model gas and bromothymol blue dye as the sensing material. The dye’s color change, indicative of pH shifts due to CO2 absorption, is captured with a digital microscope and analyzed via the ImageJ software package v1.54g. The response shows saturation and regeneration parts when cycled between CO2 and N2, respectively. Experiments are conducted to investigate the response characteristics and saturation rate under different conditions, including changes in volumetric flow rate, gas stream velocity, and dye solution volume. We observe experimentally that an increase in volumetric flow rate decreases the delay and increases the saturation rate of the response, surpassing the impact of the gas stream’s increased velocity. Furthermore, increasing the dye volume results in an exponential decrease in the saturation rate and an increase in the delay. These insights are essential for optimizing the platform’s response for point-of-use applications.

Novel Green Screen-Printed Potentiometric Sensor for Monitoring Antihistamine Drug Chlorphenoxamine HCl in Various Matrices

The pharmaceutical sector is seeking cost-effective analyzers that deliver precise, real-time data. This study aims to establish a correlation between the pharmaceutical industry and advancements in solid-contact ion-selective electrodes for quantifying chlorphenoxamine hydrochloride (CPX) concentration in various matrices. A comparative analysis of the performance between solid contact and liquid contact sensors showed that solid contact sensors outperformed their liquid contact counterparts in terms of durability, handling, and ease of integration. A sensor was developed using MWCNT and calix[8]arene as ionophore, resulting in a Nernstian potentiometric response for CPX across a linear range of 5.0 × 10−5 to 1.0 × 10−8 M. The slope of the response was 57.89 ± 0.77 mV/decade, and the standard potential was determined to be 371.9 ± 0.8 mV. The developed sensor exhibits notable intrinsic advantages, such as a rapid response time of 12 ± 2 s and an extended lifespan of 3 months. The sensor exhibiting optimal performance has been effectively employed for the analysis of CPX in different matrices, including pharmaceutical formulations, urine, and plasma. The developed method underwent validation in compliance with ICH requirements. Finally, the method’s greenness and whiteness were evaluated using five different tools and successfully compared to those obtained from the established reported method.

Study of Condensation during Direct Contact between Steam and Water in Pressure-Relief Tank

Direct contact condensation (DCC) is a phenomenon observed when steam interacts with subcooled water, exhibiting higher heat and mass transfer rates compared to wall condensation. It has garnered significant interest across industries such as nuclear, chemical, and power due to its advantageous characteristics. In the context of pressure-relief tanks, understanding and optimizing the DCC process are critical for safety and efficiency. The efficiency of pressure-relief tanks depends on the amount of steam condensed per unit of time, which directly affects their operational parameters and design. This study focuses on investigating the direct gas–liquid contact condensation process in pressure-relief tanks using computational fluid dynamics (CFD). Through experimental validation and a sensitivity analysis, the study provides insights into the influence of inlet steam parameters and basin temperature on the steam plume characteristics. Furthermore, steady-state and transient calculation models are developed to simulate the behaviour of the pressure-relief tank, providing valuable data for safety analysis and design optimization. There is a relatively high-pressure area in the upper part of the bubble hole of the pressure-relief tube, and the value increases as it is closer to the holes. The steam velocity in the bubbling hole near the 90° elbow position is higher. This study contributes to the understanding of steam condensation dynamics in pressure-relief tanks. When the steam emission and pressure are fixed, the equilibrium temperature increases linearly as the initial temperature increases (where a = 1, b = 20 in y = a x+ b correlation), the equilibrium pressure increases nearly exponentially, and the equilibrium gas volume decreases. When the steam emission and initial temperature are fixed, the equilibrium temperature does not change as the steam discharge pressure increases. The correlations between the predicted equilibrium parameters and the inlet steam parameters and tank temperature provide valuable insights for optimizing a pressure-relief tank design and improving the operational safety in diverse industrial contexts.

Determining the Reactivity of Selected Biomass Types Considering Their Application in Pyrometallurgical Processes of Metal Production.

In this paper, results of research on the reactivities of selected biomass types considering their application in pyrometallurgical processes of metal production are presented. Walnut shells, sunflower husk pellets and spent coffee grounds were selected as biomass materials. Their use as potential reducers in the process of metallurgical slag decopperisation is an innovative approach to this subject. The thermogravimetric findings show that all three tested biomass types are classified as highly reactive. The time to reach maximum reactivity ranges from 1.5 to 3 min and, the lowest value is recorded for the sample of spent coffee grounds. The sample hold time of two hours enables copper content reduction to approx. 1 wt% for practically all the reducers tested. A longer duration of liquid slag contact with the reducer results in a decreased copper content in the slag to a value below 1 wt%. Copper concentrations of 0.5 wt% and lower are observed with a hold time of 4 h. The preliminary results indicate that there is great potential for the use of this type of material in non-ferrous metallurgy, which may translate into replacing fossil raw materials and thus introducing the principles of a sustainable process in this case of metal production.

Approximate expressions for the capillary force and the surface area of a liquid bridge between identical spheres

AbstractWe consider a liquid bridge between identical spheres and present approximate expressions for the capillary force and the exposed surface area of the liquid bridge as functions of the liquid bridge’s total volume and the sphere separation distance. The radius of the spheres and the solid–liquid contact angle are parameters that enter the expressions. These expressions are needed for efficient numerical simulations of drying suspensions and other systems involving liquid bridges whose volume or shape vary in time.

MASSTRANSFER FEATURES IN THE APPARATUSES WITH A MOVING NOZZLE IN A THREE-PHASE FOAM LAYER

The improvement of heat and mass exchange equipment for sorption processes in the countercurrent contact of gas and liquid in combined block elements with a weighted spherical nozzle, as well as a more in-depth study of this process, is an urgent task of chemical technology. A fundamentally new type of ball-shaped three-dimensional mesh fluidized nozzle was developed and researched, the bodies of which are made of polymer layers with holes, and a freely coiled metal or polymer mesh is located inside. The nozzle has a high specific surface area, developed free volume and low bulk density. The study of mass transfer in the liquid and gas phases was carried out and the corresponding calculation equations were obtained. Dependencies for the calculation of the mass transfer coefficients and the efficiency of the combined block element on the mode and design parameters are established. The results of calculations based on the obtained dependencies show a sufficient correlation with the experimental data. The proposed model of the desorption process of carbon dioxide from water, which allows predicting the values of the efficiency indicators of the decarbonization process. It was established that the use of a combined block element with a ball-shaped nozzle allows to increase the mass transfer coefficients compared to the failure plate. The industrial implementation of absorption processes in the foam layer and the use of the gas-liquid layer stabilization method significantly expands the scope of application of foam apparatuses and opens up new opportunities for intensifying technological processes. Previously expressed assumption about the perspective of using mesh materials for the manufacture of nozzle bodies was confirmed by experiments, but the peculiarity of the operation of devices with similar nozzles should be emphasized.

Theoretical and experimental studies of NO removal in alkaline H2O2 system

NO in flue gas is one of the atmospheric pollutants, and it is necessary to study effective NO removal technology. It was identified that the alkaline H2O2 system achieved over 98 % NO removal efficiency with a gas–liquid contact time of 3 s in this paper. This paper investigates the mechanism of NO removal in alkaline H2O2 solution through both experimental and theoretical calculations. The results reveal the NO removal process can be divided into three phases by the NaOH/H2O2 molar ratio. (1) The ∙O2– dominated phase, where trace metal Fe catalyzes ∙O2– radical generation from H2O2 as Fe (OH)2+, reacting primarily with NO to form ONOO–. The energy barrier for this process is1.299 kcal/mol, with a reaction rate constant of 9.12 E + 11 s-1M−1. (2) The HO2– dominated phase, HO2– was generated through OH– and H2O2 neutralization, which converts NO to NO2 and regenerating OH–. The energy barrier for HO2– reacting with NO is 3.833 kcal/mol, and the reaction rate constant is 2.07E + 10 s-1M−1. (3) The O22– dominated phase, O22– was a further ionization of HO2– and converting NO to NO2– directly. The energy barrier for this process is 7.079 kcal/mol, and the reaction rate constant is 1.49 E + 08 s-1M−1.

Selection of second step micro-morphology for anti-icing surfaces based on icing time

Superhydrophobicity are associated with surface two-step micro/nanostructure together morphology. However, it is uncertain for Superhydrophobic surface (SHS) whether having anti-icing ability if without detailed knowledge of the surface morphology. For this reason, we proposed a three-dimensional (3-D) icing model to analyze anti-icing properties and determine the second step morphology suitable for the anti-icing. Followed by it, representative samples (hydrophobic or hydrophilic, metal or nonmetal, organic or inorganic) were selected for freezing measurement to confirm theoretical results. Ranked order is a sine wave/cone frustum/prism/cylinder/cuboid/paraboloid, and a semi-sine-wave model by the anti-icing time from high to low. The anti-icing property still depends on the surface micro-scale and micro-morphology to a great extent as hydrophobicity does. Effect of morphology on anti–icing will be significantly reduced even neglected, if the solid–liquid contact fraction being small enough. Meanwhile we also found that both the time for drop in temperature and the icing time are directly related to the solid fraction, whether the freezing singularity appears depends on freezing velocity or hydrophilicity. The predictions of the model largely agree with the experimental observations, also opening up possibilities for rational design of anti-icing SHS by selecting suitable morphology in micro scales.

On Spontaneous Dispersion as a Cause of Microstratification of Metal Melts.

The phenomenon of spontaneous dispersion is considered as the cause of the microstratification of metal melts. In a microstratification melt, a violation of long-range order in the arrangement of atoms (LRO) is observed, which corresponds to a dispersed particle size of more than 2 nm. Microseparation occurs due to spontaneous dispersion upon contact of liquid and solid metal or the mixing of two liquid metals. The possibility of spontaneous dispersion was assessed using three different criteria: Volmer's cr iterion, Rehbinder's criterion and the diffusion rate criterion. The diffusion rate criterion was obtained on the basis of the theory of rate processes, which describes how diffusing atoms overcome the interphase boundary. It has been established that Al-Sn melts contain colloidal-scale particles (4 nm), and Al-Si and Al-Ge melts contain atomic-scale particles (0.1 nm). For a system with a continuous series of Cu-Ni solid solutions in dispersion (Cu10Ni90-Cu20Ni80), the particle size is 2 nm. The particle size of the ternary eutectic GaInSn in the dispersion (Ga50In50-Ga50Sn50) is 5.6 nm, and the size of immiscible Cu-Fe melts in the dispersion (Cu80Fe20-Cu60Fe40) is 4.8 nm. Long-range order violations (LRO) and the presence of microlayering with colloidal particles larger than 20 nm were observed in the GaInSn ternary eutectic, in the Al-Sn simple eutectic with the preferential interaction of similar atoms, and in Cu-Fe melts with a monotectic phase diagram.

The effect of turbulence on the minimum thickness of a liquid film flowing down a vertical tube

When a liquid flows down a vertical tube at a low flowrate, it may not be able to completely cover the surface as a film, and the flow will comprise a number of rivulets separated by unwetted areas. Predictions of the minimum film thickness and corresponding minimum flowrate below which films cannot be sustained are needed in many industrial heat and mass transfer operations. In this paper a model is developed using the minimum energy method to calculate the minimum film thicknesses that can be maintained for flows down a vertical tube. It is concluded that inclusion of the effect of turbulence in the model can significantly increase the values of the calculated minimum film thicknesses. In these calculations (for 100⁰C water flowing down a 6 mm inside diameter tube) the effect of turbulence increased as the tube to liquid contact angle increased. For a flow at the highest contact angle of 90⁰, the minimum film thickness increased by 22% above the laminar value and the corresponding minimum flowrate increased by 75%. The model presented in this paper can be used to calculate the thermal performance of falling film evaporators over the whole range of flowrate.

Effects of leucine on hydrate formation: A combined experimental and molecular dynamics study

Compared to conventional natural gas storage and transportation methods, hydrates offer a safer, more compact alternative with broad future potential. To enhance hydrate formation, there has been considerable interest in environmentally friendly and cost-effective amino acid promoters, such as leucine. This study utilized a transparent vessel for CH4 hydrate formation experiments, identifying the optimal 0.5–0.6 wt% leucine concentration, which led to enhanced gas consumption, shorter induction time, and maximum gas storage density. In the leucine system, hydrates exhibited distinctive branching growth on container walls, both upward and downward. The formation of numerous microchannels amplified capillary effects, enhancing gas–liquid contact and fostering hydrate formation. Simultaneously, isobaric-isothermal molecular dynamics (MD) simulations integrated system growth configurations, structural parameters, radial distribution functions, energy barriers and mean square displacements, unveiling leucine’s microscopic impact on hydrate formation. Simulation results unequivocally show that leucine significantly accelerates CH4 hydrate growth by momentarily adsorbing at the solid–liquid interface, expediting water molecule ordering into cage-like structures. Leucine also enhances water molecule structural order around the mobile leucine molecule. Moreover, leucine lowers the energy barrier for methane transitioning from gas to liquid, facilitating gas molecule diffusion into the liquid phase and affording plenty interaction time for water and methane molecules, thereby providing favorable conditions for hydrate formation. These findings provide crucial perspectives for future research in the field of eco-friendly hydrate promoters, paving the way for innovative solutions in natural gas storage and transportation.

Kinetics mechanism of pore pressure effect on CO2-water-rock interactions: An experimental study

Carbon capture, utilization and storage (CCUS) is an effective technology to reduce carbon dioxide (CO2) content in atmosphere, while due to the insufficient mastery of deterioration laws of reservoir rocks caused by CO2, the extensive application of carbon storage projects is hindered by the leakage risk. Therefore, it was aimed to study the kinetics mechanism of pore water pressure on CO2-water–rock interactions. First, the pressure effect on water–rock interactions was studied to obtain the relationship between ratio of solid–liquid contact area Ψ and pore pressure, and the controlling mechanism of Ψ on reaction rate ri was verified. On this basis, the pressure effect on CO2-water–rock interactions was further studied. Considering the effects on Ψ and solution acidity, the original CO2-applicable kinetics equation was modified to reduce the error of calculating reaction rate by 33.60% on average. Meanwhile, a forecast method was proposed for the reaction rate under different pressure conditions, and the average calculation error was 41.00% lower than that of original kinetics equation. After verifying the accuracy of these two theoretical methods to calculate reaction rate, the reliability to calculate porosity evolution process was further verified, and the calculation errors could be reduced by 29.52% and 31.81%, respectively.

Controlled condensation by liquid contact-induced adaptations of molecular conformations in self-assembled monolayers

Surface condensation control strategies are crucial but commonly require relatively tedious, time-consuming, and expensive techniques for surface-chemical and topographical engineering. Here we report a strategy to alter surface condensation behavior without resorting to any molecule-type or topographical transmutations. After ultrafast contact of liquids with and removal from surfaces, the condensation rate and density of water droplets on the surfaces decrease, the extent of which is positively correlated with the polarity of the liquid and the duration of contact. The liquid contact-induced condensation rate/density decrease (LCICD) can be attributed to the decrease of nucleation site density resulted from the liquid contact-induced adaption of surface molecular conformation. Based on this, we find that LCICD is applicable to various surfaces, on condition that there are flexible segments capable of shielding at least part of nucleation sites through changing the conformation under liquid contact induction. Leveraging the LCICD effect, we achieve erasable information storage on diverse substrates. Furthermore, our strategy holds promise for controlling condensation of other substances since LCICD is not specific to the water condensation process.

Profiles of Static Liquid-Gas Interfaces in Axisymmetric Containers with Different Accelerations.

Second-order perturbation solutions of profiles of bubbles suspended in liquid and liquid-gas interfaces when liquid all sinks in the bottom with different accelerations are derived. Six procedures are developed based on these solutions, and they are divided into two types. One type takes the coordinates of end points of profiles as input, and the other type takes liquid volume or gas volume as input. Numerical simulations are performed with the Volume of Fluid method, and numerical results are in good agreement with the predictions of these procedures. The greater the acceleration, the flatter the bubble until all liquid sinks to the bottom. Effects of acceleration on bubble shape must be considered; otherwise, it will cause a volume prediction error of up to 10%. When all liquid sinks to the bottom, predictions of liquid volume with the same liquid meniscus height as inputs differ considerably for different accelerations. The most significant change in liquid volume occurs when the bond number Bo ≪ 1. Effects of acceleration and liquid contact angle on the liquid-gas interfaces must be considered when evaluating liquid residue. These findings should be quite helpful for liquid residue measurement and fine management in spacecraft.

Anti-icing polyurethane coating on glass fiber-reinforced plastics induced by femtosecond laser texturing

Polyurethane coating has been commonly used in aerospace and construction, and enhancing anti-icing capabilities in low temperatures is crucial for preventing mechanical failures and reducing energy consumption. Utilizing a superhydrophobic surface was considered an important option to improve anti-icing performance. In this study, femtosecond laser treatment has applied to polyurethane coating on glass fiber-reinforced plastic (GFRP) to transform from hydrophilic to superhydrophobic. Results have indicated that laser treatment significantly reduced the solid–liquid contact area compared to the original surface. The non-polar groups on the surface contributed greatly to the enhancement of hydrophobicity. In comparison to the original surface, the freezing temperature of droplets on the superhydrophobic surface with improved anti-icing performance was reduced from −4.5 °C to −9.2 °C, while the freezing time was extended from 65 s to 269 s. This improvement was attributed to the reduction of solid–liquid contact area, resulting in a low heat transfer rate and a low heterogeneous nucleation rate. Additionally, the laser-treated surface exhibited excellent self-cleaning effects, along with mechanical and chemical stability.