Liquid Removal Research Articles

PFAS-CTAB Complexation and Its Role on the Removal of PFAS from a Lab-Prepared Water and a Reverse Osmosis Reject Water Using a Plasma Reactor.

Electrical discharge plasma reactors with argon bubbling can effectively treat long-chain perfluoroalkyl acids (PFAAs) in contaminated water, and the addition of a cationic surfactant cetrimonium bromide (CTAB) is known to enhance the removal of short-chain PFAAs. However, the roles of PFAA chain length, functional group, and water matrix properties on PFAA-CTAB complexation are largely unknown. This work investigated the bulk liquid removal of different PFAAs by CTAB in the absence of plasma. Stepwise addition of CTAB was subsequently used to efficiently treat PFAAs in a lab-prepared water and a reverse osmosis (RO) reject water using an enhanced contact plasma reactor. The results show that CTAB inhibited the bulk liquid removal of long-chain PFAAs in the absence of plasma likely due to the formation of hydrophilic CTAB-PFAA mixed micelles and competition for interfacial access between long-chain PFAAs and CTAB. On the contrary, CTAB enhanced the removal of short- and ultrashort-chain PFAAs by forming hydrophobic complexes. After 6 h of treatment in the plasma reactor with CTAB, PFAAs were 86 to >99% removed from the lab-prepared water and 29 to >99% removed from the RO reject water. This study provides important insights for overcoming mass transfer limitations for PFAA treatment technologies.

Multi-flow channel proton exchange membrane fuel cell mass transfer and performance analysis

This paper presents a study on the proton exchange membrane fuel cell (PEMFC) with a high humidity three-dimensional two-phase multi-channel model using COMSOL. The effects of gradient porosity in the gas diffusion layer (GDL) and gradient electrolyte volume fraction in the catalyst layer (CL) in the Y-direction on oxygen distribution, liquid water removal, current density surface area reaction rate (SCS), and current density magnitude of PEMFC are investigated. The results indicate that an appropriate gradient porosity in the GDL can improve the performance of PEMFC, especially in terms of oxygen distribution. Similarly, an appropriate gradient electrolyte volume fraction in the CL can enhance the current density uniformity. In addition, an improved multi-objective genetic optimization algorithm (RONSGA-II) is proposed in Chapter 4, along with an optimization method based on neural networks and RONSGA-II. As an example, the gradient porosity in the GDL in the Y-direction is optimized for current density and water removal. The optimized current density is increased by 1.22%, and water removal performance is improved by 16.67%.

Dependence of vapor and liquid water removal on cross-flow in polymer electrolyte fuel cell investigated by operando synchrotron X-ray radiography

Excessive liquid water in the gas diffusion layer (GDL) of a polymer electrolyte fuel cell is known to degrade the performance. Cross-flow through the GDL is applied to reduce the liquid water in the GDL. However, cross-flow has a disadvantage with a high pressure drop and is difficult in practical use. Controlled cross-flow has the possibility to reduce the liquid water, while the pressure drop remains acceptable for application. This study experimentally quantifies the amount of liquid water in the GDL by operando synchrotron X-ray radiography and the cross-flow rate with different GDL thicknesses. The relationship between the cross-flow rate and the amount of liquid water indicates that liquid water could be reduced by a smaller pressure drop with a thicker GDL. In addition, vapor removal by cross-flow is evaluated, and the relative humidity of cross-flow does not increase to 100% after flowing through the GDL containing liquid water.

Strength and deformation characteristics of slag crushed stone of coal thermal power plants

Mechanical properties of the slag crushed stone (coarse-grained ASM), formed in the course of coal combustion at Kansk-Achinsk, Kuznetsk coal deposits (in boilers equipped with liquid and dry slag removal facilities) and the application of the slag crushed stone in roadbuilding are considered. In the course of the research, the crushability and the deformation modulus of particular fractions of slag crushed stone samples taken from the dumps of Novosibirsk TPP-3 (that consumes the coal of the Kansk-Achinsk coal mining field) and from Novosibirsk TPP-2 and Seversk TPP (that consume the coal of the Kuznetsk coal mining field) were identified. To assess the factors influencing the mechanical strength of the slag crushed stone, ignition losses, the content of flaky and acicular particles, dust and clay particles and clay lumps was made. The difference in the mechanical strength of samples having different genesis was identified. The graphs obtained in the course of testing were assessed and deformability characteristics were calculated (for materials having different fineness values). The factors influencing the mechanical strength of slag crushed stone were determined. Dependencies between deformation parameters and crushability of the slag crushed stone were obtained. Some mechanical and physical parameters of the slag crushed stone were identified; they were applied to outline potential areas of the slag crushed stone application in road building. The mathematical relationship needed to project the deformation modulus of the slag crushed stone was identified. This relationship will be used to design structures to be made of this material.

Effect of humidification and cell heating on the operational stability of polymer electrolyte membrane fuel cell

Because of its clean or zero-emission nature, the PEM fuel cell is considered a potential energy conversion device for power production. The performance of the PEM fuel cell is known to be influenced by many parameters, such as operating temperature, pressure, and humidification of the reactants. In addition, the operational stability of the PEM fuel cell under these conditions with the purging of water during its operation should also be studied to understand the performance of the PEM fuel cell. Therefore, this paper brings out the effects of cell humidification and cell heating on the performance, especially the operational stability concerning the liquid water removal of the PEM fuel cell. The experiments are conducted on a single PEM fuel cell with mixed flow distributors operating on different cell temperatures and humidification conditions. At dry feed operation of the PEM fuel cell at ambient condition, the cell utilizes around 80.3% of water generated for its membrane hydration, i.e., self-humidification. When the PEM fuel cell is operated at full humidification (100% RH) on both sides, the membrane is well hydrated, and the cell attains the maximum power density of 0.25 W/cm2, which is 56% more than dry feed operation. The results of the experiments at static current density demonstrate membrane hydration is the significant factor for both stable operation and efficient power output. External purging must periodically be carried out to stabilize the cell due to voltage fluctuations. The major outcome of the current study is to establish the connection between hydration and the stability of the PEM fuel cell.

Review of Flow Field Designs for Polymer Electrolyte Membrane Fuel Cells

The performance of a polymer electrolyte membrane fuel cell (PEMFC) closely depends on internal reactant diffusion and liquid water removal. As one of the key components of PEMFCs, bipolar plates (BPs) provide paths for reactant diffusion and product transport. Therefore, to achieve high fuel cell performance, one key issue is designing BPs with a reasonable flow field. This paper provides a comprehensive review of various modifications of the conventional parallel flow field, interdigitated flow field, and serpentine flow field to improve fuel cells’ overall performance. The main focuses for modifications of conventional flow fields are flow field shape, length, aspect ratio, baffle, trap, auxiliary inlet, and channels, as well as channel numbers. These modifications can partly enhance reactant diffusion and product transport while maintaining an acceptable flow pressure drop. This review also covers the detailed structural description of the newly developed flow fields, including the 3D flow field, metal flow field, and bionic flow field. Moreover, the effects of these flow field designs on the internal physical quantity transport and distribution, as well as the fuel cells’ overall performance, are investigated. This review describes state-of-the-art flow field design, identifies the key research gaps, and provides references and guidance for the design of high-performance flow fields for PEMFCs in the future.

Numerical study on condensation heat transfer in vertical channel with hydrophilic-hydrophobic patterned surfaces

A numerical study was conducted of condensation phenomenon in a vertical channel with hydrophilic-hydrophobic patterned surfaces. The Volume of Fluid (VOF) method was adopted to detect the phase interface and the Lee's phase-change model was used. An Artificial Neural Network (ANN) model was constructed to predict the heat transfer coefficient using experimental data and model was used for the numerical validation. From the force balance around a liquid droplet, a theoretical relationship between the inflow velocity and the droplet movement angle was derived. The size, arrangement and angle of the pattern were considered as design variables, together with the channel height. The results showed that a decrease of the pattern size and increases of pattern angle and channel height caused heat transfer augmentation. In contrast, increased pressure drop was observed as the pattern size and the channel height decreased and the pattern angle increased. Bridging droplets in the channel were observed depending on the arrangement of patterns between two plates; surfaces with staggered patterns showed better performance. It was found that the thermal performance of the plate was highly influenced by the pattern angle, because of the performance of the condensate liquid removal.

Characteristics of a composite flow field with drop-shaped gas distribution zones and a honeycomb-like staggered channel for proton exchange membrane fuel cells

ABSTRACT On the basis of previous studies, a staggered honeycomb-like flow field with drop-shaped gas distribution zone is proposed in this paper, and the staggered honeycomb-like flow channel can make the oxygen concentration higher, and the drop-shaped gas distribution zone can improve the uniformity of reaction gas in the flow field. A three-dimensional (3D), non-isothermal two-phase numerical model is established to study the flow field performance. First, the reaction gases in the flow field are analyzed, and it is found that the proposed flow field structure can effectively improve the concentration and uniformity of reactants. Second, the volume fraction of liquid water at the (GDL)/channel (CH) interface is analyzed, and it is found that compared with the model of the symmetrical honeycomb channel without considering the gas distribution zone, the proposed model has better water removal effect at the cathode. Finally, the effects of the proposed flow field structure on the membrane properties are discussed. In addition, the temperature uniformity and liquid water removal of PEMFC are improved under the condition of reverse flow of cathode and anode reaction gases.

Automated One-Drop Assembly for Facile 2D Film Deposition.

The effective application of 2D materials is strongly dependent on the mass production of high-quality large-area 2D thin films. Here, we demonstrate a strategy for the automated manufacturing of high-quality 2D thin films using a modified drop-casting approach. Our approach is simple; by using an automated pipette, a dilute aqueous suspension is dropped onto a substrate heated on a hotplate, and controlled convection by Marangoni flow and liquid removal causes the nanosheets to come together to form a tile-like monolayer film in 1-2 min. Ti0.87O2 nanosheets are utilized as a model system for investigating the control parameters such as concentrations, suction speeds, and substrate temperatures. We perform the automated one-drop assembly of a range of 2D nanosheets (metal oxides, graphene oxide, and hexagonal boron nitride) and successfully fabricate various functional thin films in multilayered, heterostructured, and sub-micrometer-thick forms. Our deposition method enables on-demand large-size (>2 inchϕ) manufacturing of high-quality 2D thin films while reducing the time and sample consumption.

Modeling of solid–liquid coupling and material removal in robotic wet polishing

Modeling of solid–liquid coupling and material removal in robotic wet polishing

Machine-learning-aided application of high-gravity technology to enhance ammonia recovery of fresh waste leachate

Stripping is widely applied for the removal of ammonia from fresh waste leachate. However, the development of air stripping technology is restricted by the requirements for large-scale equipment and long operation periods. This paper describes a high-gravity technology that improves ammonia stripping from actual fresh waste leachate and a machine learning approach that predicts the stripping performance under different operational parameters. The high-gravity field is implemented in a co-current-flow rotating packed bed in multi-stage cycle series mode. The eXtreme Gradient Boosting algorithm is applied to the experimental data to predict the liquid volumetric mass transfer coefficient (KLa) and removal efficiency (η) for various rotation speeds, numbers of stripping stages, gas flow rates, and liquid flow rates. Ammonia stripping under a high-gravity field achieves η = 82.73% and KLa = 5.551 × 10−4 s−1 at a pH value of 10 and ambient temperature. The results suggest that the eXtreme Gradient Boosting model provides good accuracy and predictive performance, with R2 values of 0.9923 and 0.9783 for KLa and η, respectively. The machine learning models developed in this study are combined with experimental results to provide more comprehensive information on rotating packed bed operations and more accurate predictions of KLa and η. The information mining behind the model is an important reference for the rational design of high-gravity-field-coupled ammonia stripping projects.

Hydrogel with Robust Adhesion in Various Liquid Environments by Electrostatic-Induced Hydrophilic and Hydrophobic Polymer Chains Migration and Rearrangement.

Hydrogels with wet adhesion are promising interfacial adhesive materials; however, their adhesion in water, oil, or organic solvents remains a major challenge. To address this, a pressure-sensitive P(AAm-co-C18 )/PTA-Fe hydrogel is fabricated, which exhibits robust adhesion to various substrates in both aqueous solutions and oil environments. It is demonstrated that the key to wet adhesion under liquid conditions is the removal of the interfacial liquid, which can be achieved through rational molecular composition regulation. By complexing with hydrophilic polymer networks, phosphotungstic acid (PTA) is introduced into the hydrogel network as a physical cross-linker and anchor point to improve the cohesion strength and drive the migration of polymer chains. The migration and rearrangement of hydrophilic and hydrophobic polymer chains on the hydrogel surface are induced by the electrostatic interactions of Fe3+ , which create a surface with interfacial water- and oil-removing properties. By co-regulating the hydrophilic and hydrophobic polymer chains, the P(AAm-co-C18 )/PTA-Fe hydrogel is able to act as a pressure-sensitive adhesive under water and oils with adhesion strength of 92.6 and 90.0kPa, respectively. It is anticipated that this regulation strategy for polymer chains will promote the development of wet adhesion hydrogels, which can have a wide range of applications.

Silica Aerogel: Synthesis, Characterization, Applications, and Recent Advancements

AbstractSilica aerogels have drawn considerable attention due to their low density (almost 95% of the total volume is composed of air), hydrophobicity, optical transparency, low conductivity of heat, and large surface to volume ratio. Sol–gel processing is used to prepare aerogels from molecular precursors. To replace the pore fluid with air while retaining the solid network, a supercritical drying process (the most frequent approach) is used. However, recent technologies use atmospheric pressure to allow for liquid removal followed by chemical alteration of the gel's internal layer, which leaves only a silica network with a porous structure filled with air. This study discusses the sol–gel method for preparing silica aerogels and their various drying processes. Furthermore, various areas of applications of silica aerogels, including electronics, construction, aerospace, purification of water and air, sensing, catalyst, biomedical, absorbent, food packing, textile, etc., are also discussed. Lastly, this review provides a perception of the recent scientific progress along with the futuristic development of silica aerogel.

Simulation of liquid water removal in the gas diffusion layer with polytetrafluoroethylene random shedding using lattice Boltzmann method

Simulation of liquid water removal in the gas diffusion layer with polytetrafluoroethylene random shedding using lattice Boltzmann method

Drainage Research of Different Tubing Depth in the Horizontal Gas Well Based on Laboratory Experimental Investigation and a New Liquid-Carrying Model

Since the structure of horizontal gas wells is more intricate than that of vertical wells, there is a lack of consistency in the form of liquid-carrying in different portions. Applying the commonly utilized liquid-carrying hypothesis of vertical gas wells into horizontal gas wells is therefore challenging. The maximum liquid volume that the gas flow could raise, the gas flow rate, and the maximum amount of energy that could be produced from a specific amount of gas flow should all be considered when determining the liquid volume that the gas flow could lift. This study is the first to integrate theoretical analysis with laboratory testing to analyze the gas–liquid flow law of drainage stability at varied tubing depths. The impact of gas drainage stability is then verified through the laboratory experiments. The novel model of various tubing depths, which is based on the energy of inflow and outflow from the horizontal well, is cleverly built. According to the study, the fluctuation is typically less when the tubing reaches the heel of the horizontal section than it is in the other sections, and the relative error of the new model, which is validated using laboratory tests, is typically less than 10%. The research showed that for horizontal gas wells with a normal structure, the gas flow and liquid discharge are most stable when the tubing reaches the heel of the horizontal section. Instead of depending exclusively on crucial liquid-carrying gas flow rates, the new model uses the combination of gas and liquid flow rates to make decisions concerning liquid loading and to quantify the liquid removal in real time, which is more realistic. The research illustrates how the study could provide a factual basis for assessing the capacity of horizontal gas wells to raise the liquid.

Lunar dust removal and material degradation from liquid nitrogen sprays

Lunar regolith degrades human health and equipment making mitigation paramount for lunar missions. Cryogenic liquid sprays are a recently developed, simple, and convenient concept for dust mitigation in a lunar environment. However, removal efficacy and material degradation under the extreme cryogenic vacuum environment are unknown. Traditional space suit dust mitigation technologies used on the Apollo missions, such as brushing and vacuuming, introduced suit fabric abrasion which must be addressed for all dust mitigation methods considered for lunar implementation. This publication reports the efficacy of dust removal in a simulated airlock vacuum environment and the associated impact of repeated dusting-washing cycles on spacesuit materials. Specimens were impinged with measured liquid nitrogen sprays at different spray angles within a vacuum chamber. Mean mass removal of 98.4% was achieved in a vacuum environment at optimal conditions, correlating to 95.9% removal of particles below 10 μm. To investigate material degradation, a total of 26 samples were cycled a cumulative 233 times through cryogen spray washings under ambient conditions. A degradation scale was created to classify optical microscopy observations. Degradation results indicate minimal spacesuit material abrasion from liquid nitrogen removal. Results additionally show an average of 2.66% increased removal with each subsequent washing cycle for fabric washed twice, possibly due to clogging and occupancy of specific sites. The conclusion is that liquid nitrogen sprays cause relatively less damage than conventional dust mitigation techniques, even under the extremes of cryogenic temperatures and vacuum.

Degradation of 1-alkyl-3-methylimidazolium tetrafluoroborate in an ultrasonic zero-valent zinc and activated carbon micro-electrolysis system

Increased attention has been given to the removal of ionic liquids (ILs) from natural water environments. In this work, 5 kinds of 1-alkyl-3-methylimidazoliumtetrafluoroborate ([Cnmim][BF4] (n = 2, 4, 6, 8, 10)) ILs were degraded in an ultrasonic zero-valent zinc (ZVZ) and activated carbon (AC) micro-electrolysis system. Optimization of degradation conditions and the degradation levels were studied by high performance liquid chromatography, the surface morphology of the ZVZ and AC changed before and after the reaction were observed by scanning electron microscope. The degradation intermediates were detected by gas chromatography- mass spectrometry and ion chromatography, and inferred the degradation pathway. The degradation effect of [C4mim][BF4] was best with ultrasonic assistance, pH 3 and an AC/ZVZ ratio of 1:1. The degradation of [Cnmim][BF4] in aqueous solution exceeded 91.7% in 120 min, and the mineralization level exceeded 88.9%. The surface of smooth and dense ZVZ particles became loose flocculent and the porous surface of AC became larger and rougher after reaction. The degradation pathway suggested that the imidazolium ring was sulfurized or oxidized, and then the ring was opened to form N-alkyl formamide and N-methyl formamide. ZVZ/AC micro-electrolysis combined with ultrasonic irradiation is an effective method to remove ILs, which provides new insight into IL degradation.

Long-term Outcomes of Submacular Perfluorocarbon Liquid Removal with Internal Limiting Membrane Peeling and Transretinal Aspiration.

An important complication associated with perfluorocarbon liquid (PFCL) use during pars plana vitrectomy (PPV) is its retention in the submacular area. The aim of this study was to present the long-term outcomes of the surgical method used in this study to remove submacular PFCL and to shed light on the advantages and disadvantages compared to other methods. This is a retrospective, single-center, observational study. Patients who underwent surgical intervention due to submacular PFCL were included in this study. The surgical procedural includes internal limiting membrane (ILM) peeling, transretinal aspiration of submacular PCFL with a 25/27-gauge soft-tipped cannula, then perfluoropropane (C3F8) gas tamponade, and facedown positioning for 5 days. The long-term anatomical and functional outcomes were evaluated with an ophthalmological examination and optical coherence tomography (OCT). A total of 15 patients with submacular PFCL were included in this study, and the mean age of the patients was 64.33 ± 10.36 years (47 - 83). The localization of submacular PFCL was subfoveal in nine patients (60.00%), non-subfoveal in four patients (26.67%), and both subfoveal and non-subfoveal in two patients (13.33%). The mean time of submacular PFCL diagnosis was 4.86 ± 1.02 weeks (2 - 8) and the mean time of the surgery was 9.80 ± 1.17 weeks (8 - 14). Complete removal of submacular PFCL was achieved in all cases (100%) and no significant treatment-associated complications were observed. The mean follow-up time was 37.60 ± 14.00 months (18 - 60) and the best-corrected visual acuity was significantly improved (p = 0.001). At the end of the follow-up time, prominent ellipsoid zone disruption was observed in six patients (40.00%), while in nine patients (60.00%), there was no prominent ellipsoid zone disruption. The surgical procedural for submacular PFCL removal is a reasonable option and improves visual acuity in the long term without any significant treatment-associated complications.

Numerical experiments on the determination of rational range of mode parameters for the effective dewatering of various screening surfaces

Dehydration of mineral raw materials on a vibrating screen occurs as a result of the passage of liquid through the cells of the screening surface. With fine and ultrafine screening, this process is hindered by the surface tension of the liquid. None of the screening theories makes it possible to determine which vibration excitation modes ensure dehydration. With the help of numerical experiments on a mathematical model, the influence of vibration excitation modes on the intensity of the passage of liquid through the cells of various screening surfaces during dehydration on a vibrating screen was studied. In doing so, two tasks were solved: 1) determination of the amplitude and frequency of vibration excitation, when the required balance of water and the size of the cells of the screening surface are set; 2) determination of the remaining water on the screening surface depending on the cell size of the screening surface, the amplitude and frequency of vibration excitation. The developed mathematical model made it possible to solve both problems. On the basis of calculations and analysis, rational range of mode parameters of the vibrating screen for effective dehydration of various screening surfaces was established. The calculation algorithm is implemented on the basis of a mathematical model in the PC program «Sifting Surface» in C ++ with the connection of mathematical libraries and «Excel». The results of calculations, demonstration of the possibilities of various screening surfaces and modes are shown in the figures, which show the dependences of the residual water on the amplitude and frequency vibration excitation parameters. It is established that the vibro-impact effect, in comparison with the harmonic effect, provides better results in cleaning the cells from the liquid retained in them by surface tension forces, under less intensive modes. The results obtained will be used in the development of a mathematical model of dehydration and a method for calculating technological parameters that ensure effective removal of liquid during fine and ultrafine screening of mineral raw materials, as well as to determine the rational design and dynamic parameters of the screen.

Three-dimensional simulation of large-scale proton exchange membrane fuel cell considering the liquid water removal characteristics on the cathode side

A 3D (three-dimensional) numerical simulation model is proposed to investigate the output performance and liquid water distribution of large-scale FF (flow field) considering DMGDZ (“dot matrix” gas distribution zone). The PEMFC (proton exchange membrane fuel cell) is affected by gravity, and the simulation results demonstrate that the PEMFC has the best output performance and water removal effect when the length and width of DM (“dot matrix”) are 1.5 mm and 0.8 mm, respectively. The effect of gravity direction on liquid volume fraction in cathode large-scale FF is not obvious, but liquid volume fraction increases with the increase of the contact angle of GDL (gas diffusion layer) and working current density. The variation of water vapor condensation rate and the MPL (micro-porous layer) contact angle in porous electrodes significantly affects the amount of liquid water in the CFF (cathode flow field), and the PEMFC performance is degraded. Due to the enhancement of convection effect, the waveform channel can effectively remove the liquid water from the cathode channel and slightly strengthen the overall PEMFC performance. According to the results of waveform channel analysis, the comparison of waveform and straight FFs with DMGDZ shows that the waveform FF is more conducive to facilitate the liquid water removal on the cathode side. Simultaneously, the reactant gas distribution is uniform and the output performance is higher.