Liquid Diffusion Research Articles

Sorption kinetics and stability of conventional adsorbents for mercury remediation

In-situ remediation of mercury at numerous contaminated sites worldwide is a challenging and costly endeavor due to the persistency of this contaminant. In this study, we evaluated eight commercially available sorbent media ranging from carbon-, clays- and silica-based materials (PBC– Biochar, eSorb – Sorbster, nsPAC – Powdered Activated Carbon, fsPAC – Powdered Activated Carbon with Mackinawite, F300 – Filtrasorb 300, Si-SH – Silica Thiol, eBind – RemBind, Q-Clay – Organoclay PM-199), for their effectiveness in sorbing mercury (Hg2+) and mercury complexed with dissolved organic matter (Hg-DOM). Under the chosen experimental conditions of this study, results showed that in the absence of DOM, the kinetic rates of Hg2+ sorption onto the evaluated sorbents were in the order of 0.31 min−1(Si-SH) to 2.98 min−1 (nsPAC), whereas in the presence of DOM, the rates varied from 0.16 min−1 (F300) to 0.95 min−1 (nsPAC). The measured sorption capacity for Hg2+ in the absence of DOM varied from 3.02 mg/g (Q-Clay) to 35.15 mg/g (Si-SH), whereas in the presence of DOM, calculated partition coefficient (KD) ranged from 69.7 mL/g (Q-Clay) to 41,510 mL/g (Si-SH). Furthermore, kinetic data suggest liquid film diffusion was the rate-limiting steps governing mercury sorption onto the studied media. Overall, the obtained study parameters (kinetics/isotherm) are particularly important in informing robust engineering designs for deployment of the vast majority of evaluated sorbents. Thus, sorbent-based strategies offer viable solutions for cost-effective cleanup of mercury at industrially contaminated sites.

Study on the adsorption performance of zeolite imidazole frameworks materials for Co(II) and Mn(II) in solution

Abstract The radionuclides 60Co and 54Mn are the main activation products produced in the operation of nuclear power facilities. Wastewater with these radionuclides must be treated to meet standards before being discharged. A variety of zeolite imidazole frameworks (ZIFs) materials were synthesized at room temperature, and the adsorption effect of ZIF-67 was found to be the best through adsorption experiments on Co(II) and Mn(II). The thermal stability test and structural characterization of ZIF-67 were carried out. At the same time, the influence of the initial pH value, adsorption time, and initial concentration of the solution on the adsorption of Co(II) and Mn(II) by ZIF-67 was investigated. The results show that: ZIF-67 has a microporous structure with a BET surface area of 1,035.72 m2/g. In addition, ZIF-67 has good thermal stability, under the condition of pH = 6, a temperature of 303 K and the initial concentration of 500 mg/L. The saturated adsorption capacity for Co(II) and Mn(II) reached 230.25 mg/g and 338.75 mg/g, respectively. ZIF-67 exhibits good selective adsorption performance for Co(II) and Mn (II) in high concentration interfering ion solutions and multi-ion solutions. The adsorption process of ZIF-67 was analyzed by kinetics, thermodynamics, isotherms, and adsorption diffusion models. The analysis of thermodynamic parameters shows that the adsorption process of ZIF-67 to Co(II) and Mn(II) is spontaneous and endothermic. The pseudo-second-order kinetic model, Langmuir isotherm model, and Boyd model are more in line with the adsorption process of Co(II) and Mn(II) by ZIF-67. It shows that the active sites on the surface of ZIF-67 are evenly distributed, and the adsorption process is single-molecule chemical layer adsorption. In addition, the liquid film diffusion dominates the adsorption rate during the adsorption process of Co(II) and Mn(II) by ZIF-67.

Green Synthesis of Antimicrobial Silver Nanoparticles using Green Tea Extract: The Role of Concentration and pH

ABSTRACTGreen synthesis for silver nanoparticles (AgNPs) is the process of reducing Ag+ ions to Ag0 by using plant bioactive compounds. Green synthesis is safer, environmentally friendly and cost-effective. Plant bioactive compounds from Camellia sinensis L. (green tea) extract containing polyphenols can be used as a reducer in the formation of silver nanoparticles. This study aims to determine the effect of pH (8, 9, and 10), at 1,5mM AgNO3 concentration and 0,75% green tea extract concentration on the physical characteristics and antibacterial activity of silver nanoparticles prepared by green synthesis method. The synthesized results were evaluated by UV-Vis Spectrophotometer, Dynamic Light Scattering (DLS), SEM, and FTIR. The optimal AgNP synthesis process resulted from the AgNO3 concentration of 1.5 mM with 0.75% green tea extract at pH 10 which showed an absorbance value of 4,420 at λ 435,3 nm, with a particle size of 47,1 nm and a PDI of 0,243. The formation of AgNPs was observed by a change in color to brownish yellow. Antibacterial activity of AgNPs using liquid diffusion method. The results obtained AgNPs for Staphylococcus aureus bacteria has had inhibition at a concentration of 0,187mM and Escherichia coli at a concentration of 0,375mM.Keywords: Silver nanoparticles; green synthesis; green tea extract; pH; antibacterial activity

Effect of porosity and temperature on viscosity and diffusivity of benzene liquid containing nanobubble with molecular dynamics

Introduction of nanobubble (NB) into liquid can significantly affect the transport properties such as viscosity and diffusivity, being important in the design and optimization of many liquid-related industrial processes. The present paper reports the atomistic insights into influence of porosity (volume fraction of NBs in solution) and temperature on viscosity and self-diffusion coefficient in benzene liquid containing NBs by using molecular dynamics (MD) simulation with the COMPASS force field. We make molecular modeling of NB-containing benzene liquid using the cubic box with porosities increasing from 0 to 24.6% and conduct a series of MD simulations as increasing temperature from 298 to 343 K. Our simulations reveal that as increasing the porosity the viscosity decreases according to the cubic polynomial while the self-diffusion coefficient increases rapidly. When compared with high polar NB aqueous solutions, although the changing tendencies of transport properties are similar, the changing degrees in benzene liquid are clearly higher, indicating that NB creation has a stronger influence on transport properties of non-polar benzene liquid due to the weaker intermolecular interaction. Meanwhile, as increasing temperature, the viscosity decrease while the self-coefficient increases, both according to the Arrhenius equation. Such temperature dependence is similar to aqueous solution, meaning that temperature affects the transport properties of polar and non-polar liquids alike. This work will contribute to developing NB utilization to practical applications.

Stagnant liquid layer as “Microreaction System” in submerged plasma Micro-Jet for formation of carbon quantum dots

This study aims to intensify reactivity via bespoke transient hydrodynamics in a plasma-activated three-phase catalyst system. Likewise, three-phase plasma systems in literature are not well designed, understood and commercially available. The synthesised N-doped carbon quantum dots, with application as fertilisers and wastewater treatment was evaluated as a model reaction. A plasma microjet was produced using a commercial plasma system, creating an almost flat, large interface covering a thin stagnant liquid layer with a catalyst bed underneath. In this hydrodynamic regime, plasma can penetrate the catalyst bed via the stagnant thin liquid film and polarise the plasma-liquid interface. The new process regime’s effectiveness is proven by the enhanced reaction rate achieved by raising liquid diffusivity toward the catalyst bed through solvent viscosity reduction. Results indicate that the reaction rate depends on the small surface area interacted with the plasma jet amid an excess of excited species, not the total gas–liquid interface area. The plasma process competes energetically with the best dielectric barrier discharge processes and uses less energy than microfluidic processing in chemical microreactors. High momentum transfer from the plasma jet to the liquid partly evaporates non-water additives, impacting process design and requiring reduction.

Study on Liquid Hydrogen Leakage and Diffusion Behavior in a Hydrogen Production Station

Liquid hydrogen storage is an important way of hydrogen storage and transportation, which greatly improves the storage and transportation efficiency due to the high energy density but at the same time brings new safety hazards. In this study, the liquid hydrogen leakage in the storage area of a hydrogen production station is numerically simulated. The effects of ambient wind direction, wind speed, leakage mass flow rate, and the mass fraction of gas phase at the leakage port on the diffusion behavior of the liquid hydrogen leakage were investigated. The results show that the ambient wind direction directly determines the direction of liquid hydrogen leakage diffusion. The wind speed significantly affects the diffusion distance. When the wind speed is 6 m/s, the diffusion distance of the flammable hydrogen cloud reaches 40.08 m, which is 2.63 times that under windless conditions. The liquid hydrogen leakage mass flow rate and the mass fraction of the gas phase have a greater effect on the volume of the flammable hydrogen cloud. As the leakage mass flow rate increased from 5.15 kg/s to 10 kg/s, the flammable hydrogen cloud volume increased from 5734.31 m3 to 10,305.5 m3. The installation of a barrier wall in front of the leakage port can limit the horizontal diffusion of the flammable hydrogen cloud, elevate the diffusion height, and effectively reduce the volume of the flammable hydrogen cloud. This study can provide theoretical support for the construction and operation of hydrogen production stations.

Ionic liquids functionalized chitosan: An effective, rapid and green adsorbent for gold recovery

Thiosulfate has been considered as a more environmentally-friendly alternative to cyanide salts for the extraction of gold from gold ores and the development of affordable, green and efficient adsorbents for the isolation of gold-thiosulfate complex (Au(S2O3)23−) from the leaching solution remains a significant challenge. To address this issue, chitosan, a natural macromolecule, was selected as a carrier and chemically modified with ionic liquids. The ionic liquids modified chitosan showed greater adsorption capacity towards Au(S2O3)23− compared with pristine chitosan. The adsorption of Au(S2O3)23− on ionic liquid modified chitosan followed Freundlich isotherm and pseudo-second order kinetic models, involving an anion-exchange mechanism with liquid film diffusion as the rate-limiting step. The chitosan modified with butylimidazolium-based ionic liquid had an adsorption capacity of 5.0 mg g−1 for gold (10 mg L−1 of gold, pH 6, 2 g L−1 of adsorbent dosage), outperforming other reported adsorbents. The ionic liquid modified chitosan showed a high adsorption efficiency of up to 96.7 % for Au(S2O3)23− in an actual thiosulfate leaching solution with a desorption efficiency of 98.4 %, suggesting that the ionic liquid modified chitosan has the potential to be a eco-friendly, biocompatible and effective adsorbent for the recovery of Au(S2O3)23−.

Topical Delivery of Voriconazole Loaded on Lyotropic Liquid Crystal Gel for Management of Fungal Infections

Topical antifungal therapy is recommended for the treatment of fungal infections of the skin. Due to its benefits, including the ability to direct drugs to the infection site and a lower chance of systemic adverse effects. The nano size and structure of LLC with the skin enhance the permeation and deposition of drugs within deep parts of skin. In this a novel formulation of voriconazole LLC gel was planned. Surfactant, co-surfactant, oil, and water pseudo-ternary phase diagrams were created in order to determine the LLC gel and microemulsion zones. The formulations were evaluated using polarizing microscopy, FT-IR spectroscopy. For each formulation, the polydispersity index, zeta potential, and mean droplet size were determined. The release patterns revealed that the prepared LLC gel provide sustained release profile up to 24 hr. Ex-vivo permeation of selected formulations exhibited higher permeability values for voriconazole. The drug skin deposition results from selected formulations showed that, in comparison to other studied formulations, a much larger amount of the drug was deposited in the skin after 24 hours. The confocal pictures appeared that the LLC gel was able to provide fluorescent color to all skin layers. The skin irritation study data of LLC gel formulations could be announced as safe and non- irritant for human skin. The selected formulations underwent a six-month stability testing at room temperature and 4–8 °C. The results showed that the pH, drug content, and viscosity values did not change significantly during this time. Keywords: Lyotropic liquid crystal, Release and diffusion, Skin permeability, Skin deposition, Pathohistology

Enhancing sludge hot-pressing drying by sawdust: Sensitivity analysis of heat and mass transfer physical properties of sludge, process performance, and kinetics

Hot-pressing drying shows promise in sludge treatment. Optimization often focuses on temperature and external load. However, the impact is restricted by sludge inherent properties, which can be changed by sludge conditioning. Due to coupling effects, altering individual sludge properties is difficult. Key sludge properties that significantly affect heat and mass transfer remain unclear, hampering identification of specific conditioning techniques. To address this gap, the effects of sludge specific heat, thermal conductivity, water activity, moisture diffusivity, and moisture permeability on drying performance were explored using sensitivity analysis. Sawdust conditioning and kinetics were employed to improve drying performance, validate sensitivity analysis findings, and elucidate drying mechanisms. Sensitivity analysis revealed that liquid water permeability significantly positively influenced drying performance by enhancing liquid water convection. Sawdust conditioning and kinetics demonstrated that adding 20 % sawdust increased drying flux from 31 to 62 kgwater·m⁻²·h⁻¹. The drying process included warm-up and constant rate, the first falling rate, and the second falling rate periods. Enhanced moisture transfer was dominated by breakthrough of interfacial gas film, transformation from liquid water diffusion to convection, and facilitated water vapor diffusion, respectively. Hence, this study provided novel insights, strategies, and direction of guidance for revealing sludge drying mechanisms and improving drying performance.

Improved reliability and availability of fundamental properties for all hydrogen isotopologues by Gaussian process regression using data from experiments and path-integral simulations

The thermodynamic and transport properties of hydrogen isotopologues in the solid, liquid, and gas phases are crucial for hydrogen energy exploitation, such as the design of the fuel cycle of nuclear fusion reactors. However, experimental data for tritium-containing species are often not available. Alternatively, path integral (PI) simulation can evaluate hydrogen properties taking into account nuclear quantum effects; however, concerns about its reliability are present. This study proposes a method of Gaussian process regression (GPR) using both experimental and PI simulation data to obtain practically plausible estimates for all isotopologues. Using liquid viscosity and diffusivity as test cases, we demonstrate that the present method has high and robust predictive performance. The method has broad applicability and can also be used to design experiments and calculations to efficiently improve the regression model, and thus is expected to contribute to enhancing the availability and reliability of the hydrogen isotopologue property database.

Potential Use of Jerangau Rhizome (Acorus calamus L.) as an Antibacterial Agent for Streptococcus pneumoniae

Aims: The empirical use of jerangau rhizomes for treating pneumonia in Indonesia should be verified through scientific research. Study design: The experimental use of Streptococcus pneumoniae (SP) bacteria and jerangau (Acorus calamus L.) rhizome extract (JRE). Place Study: Pharmacy Department, Poltekkes Kemenkes Makassar, Indonesia. Methodology: Antibacterial activity was assessed using liquid dilution and agar diffusion methods. Results: The antibacterial activity of JRE against SP was determined to be effective at concentrations of 0.5%, 1%, 2%, 4%, and 8% w/v. The minimum inhibitory concentration (MIC) and minimum kill concentration (MKC) were found to be 0.5% and 1% in HJ, >2.5% at EJ, and 0.25% and 0.5% at EAJ. Conclusion: JRE has demonstrated antibacterial properties against SP in vitro.

Drying kinetics and thermodynamic properties of jabuticaba peel

Jabuticaba is a fruit of high nutritional value, and the peel, which is usually discarded, contains nutrients in greater concentration. An alternative for the use of jabuticaba bark is the preparation of flour. The aim of this research was to analyze the drying kinetics of jabuticaba bark by adjusting mathematical models and determining the effective diffusion coefficient, activation energy, and thermodynamic properties at different drying temperatures. The jaboticaba residues were dried in a forced ventilation oven at different temperatures of 45, 55, 65, and 75°C. Among the various models analyzed, Page was employed to streamline the drying phenomenon. The research observed that effective diffusion coefficient decreased with increasing temperature, and the activation energy for the liquid diffusion on drying was 32.63 kJ mol-1. Furthermore, enthalpy and entropy decreased with increasing drying temperature, while Gibbs’ free energy increased with increasing drying temperature.

New insights into hydration shells in boosting marine uranium adsorption kinetics

Identifying mass transfer is essential for boosting adsorption kinetics. The internal and external diffusions serve as rate-limiting steps. The liquid film diffusion is commonly identified as external diffusion, while the mass diffusion across the ubiquitous hydration shell is generally ignored. Charged functional groups can bind water molecules strongly via electrostatically induced hydration. Herein, three representative polar polymers, including cation polymer (PDMAPAA), anion polymer (PSS) and zwitterion polymer (PSBMA), are crosslinked with polyamioxime (PAO) to synthesize radially aligned PAO-PDMAPAA, PAO-PSS, PAO-PSBMA, respectively, by a bidirectional freeze-casting. We focus on the effect of hydration structure and hydration dynamics on marine uranium extraction performance. It is found that the external diffusion in PAO-polar polymer adsorbents can be facilitated due to fast water exchange in dynamic hydration shell, leading to a reduced adsorption equilibrium time compared with the pristine PAO. However, the high hydration degree causes strong viscous shear and high dehydration barrier, which impede the complexation of UO22+ with binding sites of PAO. Although the hydration degree follows the order of PAO-PSBMA > PAO-PDMAPAA > PAO-PSS, PAO-PDMAPAA delivers the shortest equilibrium time required. In addition, the increasing temperature would weaken viscous shear in static hydration shell, which equivalently reduces the apparent friction of hydrated uranyl ions. Consequently, light-irradiated GO@PAO-PDMAPAA adsorbent, in which GO acts as a photothermal mediator, yields a shorter equilibrium time (∼18 days) than PAO-PDMAPAA together with a high uranium adsorption capacity of 12.24 mg-U/g-Ads in natural seawater. These findings provide valuable guidance for enhancing uranium adsorption kinetics associated with hydration shell.

Enhancement of long-wave vibronic interaction and quantum diffusion in liquids

The zero-phonon type hoping motion of atoms in the solid and liquid phases, causing quantum diffusion, is considered. It was found that due to the previously discovered significant enhancement of vibronic interaction with long-wave acoustic phonons, this motion in liquids can be significantly amplified compared to the solid phase of the same substance at a close temperature. Quantum diffusion may be particularly important in superfluid He.

Hygroscopic cooling (h-cool) fabric with highly efficient sweat evaporation and heat dissipation for personal thermo-moisture management

Moisture evaporation plays a crucial role in thermal management of human body, particularly in perspiration process. However, current fabrics aim for sweat removal and takes little account of basic thermo-regulation of sweat, resulted in their limited evaporation capacity and heat dissipation at moderate/intense scenarios. In this study, a hygroscopic cooling (h-cool) fabric based on multi-functional design, for personal perspiration management, was described. By using economic and effective weaving technology, directional moisture transport routes and heat conductive pathways were incorporated in the construct. The resultant fabric showed 10 times greater one-way transport index higher than cotton, Dri-FIT and Coolswitch fabrics, which contributed to highly enhanced evaporation ability (∼4.5 times than cotton), not merely liquid diffusion. As a result, h-cool fabric performed 2.1–4.2 °C cooling efficacy with significantly reduced sweat consuming than cotton, Dri-FIT and Coolswitch fabrics in the artificial sweating skin. Finally, the practical applications by actually wearing h-cool fabric showed great evaporative-cooling efficacy during different physical activities. Owing to the excellent thermo-moisture management ability, we expect the novel concept and construct of h-cool fabric can provide promising strategy for developing functional textiles with great “cool” and comfortable “dry” tactile sensation at various daily scenarios.

On Multi-Component Gas Migration in Single-Phase Systems

The present work deals with diffusion of gases in fully saturated porous media. We test and validate the gas transport mechanism of dissolution and diffusion, implemented in the TH2M process class in the open-source finite-element software OpenGeoSys. We discuss the importance of gas diffusion for the integrity of the multi-barrier system. Furthermore, we present a multi-component mass balance equation implementation in Python, which serves as a reference for the two-component TH2M implementation and allows for a discussion of multi-component gas diffusion in liquids. We verify and validate the numerical implementations as follows: First, we come up with a set of numerical benchmarks in which solutions obtained by the two-component TH2M and multi-component implementations are compared. Thus, we show under which conditions predictions made by the TH2M model can be used for multi-component gas systems. Finally, the work is validated using a through diffusion experiment performed at Belgium’s Nuclear Research Centre SCK CEN and a sensitivity analysis is conducted based on the featured experiment. The results of this work illustrate that predictions by both the two- and four-component models match the laboratory findings very well. Therefore, we conclude that also the two-component implementation can reflect the multi-component processes well under the given constraints such as full saturation.

Study of the drying kinetics of black mulberry (Morus nigra L.) leaves

Black mulberry leaves have been used to promote health and prevent diseases due to their biological properties. Drying leaves allows greater stability during storage and marketing. However, studying this operation is important to ensure that the properties are maintained. Therefore, the objective of this study was to use mathematical modeling to define the model that best fits to the experimental data of the drying kinetics at temperatures of 40, 50, 60, and 70°C. Liquid diffusion, leaf surface area, the relationship between temperature increase and diffusion coefficient, and energy activation were also determined. Among the mathematical models studied, the Page model was the one that best described the drying process of black mulberry leaves. As for the diffusion coefficient, the values increase as the drying temperature increases. The activation energy was 65.418 kJ mol-1, and it was observed that the lower the activation energy, the greater the water diffusivity in the product. The drying kinetics data of black mulberry leaves allowed a better understanding of this operation in a matrix with wide application potential. Drying black mulberry leaves at different temperatures altered their color. Considering the evaluations, temperatures of 40 and 50°C are the most indicated for drying black mulberry leaves.

Gaseous Diffusion of a Volatile Liquid in Air

طبقت هذه الدراسة ثلاث طرق نظرية لإيجاد قيمة معامل إنتشار الغازات الناتج من تبخر السوائل المتطايرة ، وتم استخدام مادة الأسيتون كسائل متطاير في الهواء. و تم مقارنة النتائج النظرية لهذه الطرق و مقارنتها بالنتائج العملية باستخدام قياس معامل الإنتشار. أظهرت النتائج النظرية بأن دقة الطرق الثلاث كانت جيدة ، و قد تميزت طريقة هيرز سبوتز بدقة عالية مقارنة بالطرق الأخرى.

Numerical investigation of mixed convective Williamson nanofluid flow over a stretching/shrinking wedge in the presence of chemical reaction parameter and liquid hydrogen diffusion

The numerical simulation of mixed convective Williamson nanofluid flow over a stretching/shrinking wedge with chemical reaction parameters and liquid hydrogen diffusion is studied. The usage of Williamson fluid in industry has had a considerable impact on industrial processes. Chemical reactions substantially impact heat and mass transfer in hydrometallurgical industries and chemical technology. The governing equations of the inquiry are nonlinear partial differential equations with surface constraints. The similarity transformation transforms partial differential equations into nondimensional ordinary differential equations that may be solved with the MATLAB bvp5c function. Variations in nanofluid velocity, temperature, and concentration patterns are graphically represented and thoroughly examined. In the case of a stretching/shrinking wedge, the liquid velocity decreases as the Williamson nanofluid parameter values increase. The dual nature solution for the skin friction coefficient is obtained when the Williamson nanofluid parameter increases. The liquid’s temperature rises proportionately to the thermophoresis and Williamson nanofluid parameters. As the Schmidt number increases, the fluid concentration improves while the chemical reaction parameter decreases.

New Processing Route for the Production of Functionally Graded 7075 Al/SiCp Composites via a Combination of Semisolid Stirring and Sequential Squeeze Casting

Advanced processing techniques are required to produce functionally graded metal matrix composites due to the metallurgical conditions required during production. In this study, we developed a novel approach for this task by using a combination of two different methods to produce functionally graded 7075 Al/SiCp (5–20 wt.%) composites. The first process was direct semisolid stirring, which was used to prevent particle agglomeration, brittle reaction products, floating or settling of the reinforcements, and poor wettability. The second process was sequential squeeze casting, which enabled liquid diffusion between the two composite layers that were used to produce a functionally graded aluminum matrix composite. Thus, a method was developed to eliminate the problems encountered in the production of particle-reinforced metal matrix composite materials using liquid stirring methods and to produce composite materials with the desired functionally graded structure. The resulting functionally graded material was subjected to spectrometer analyses, density measurements, and metallographic examinations to determine the characteristics of its layers and interfacial zones, as well as to assess the formation of the graded structure. The results indicate the potential of using this new combined manufacturing method, which is efficient and controllable, to produce functionally graded metal matrix composites.