A. Shkolin, I. Men’shchikov, E. Khozina, A. Fomkin
Adsorption-based carbon dioxide capture, utilization, and storage technologies aim to mitigate the accumulation of anthropogenic greenhouse gases that cause climate change. It is assumed that porous carbons as adsorbents are able to demonstrate the effectiveness of these technologies over a wide range of temperatures and pressures. The present study aimed to investigate the temperature-induced changes in the dimensions of the microporous carbon adsorbent Sorbonorit 4, as well as the carbon dioxide adsorption, by using in situ dilatometry. The nonmonotonic changes in the dimensions of Sorbonorit 4 under vacuum were found with increasing temperature from 213 to 573 K. At T > 300 K, the thermal linear expansion coefficient of Sorbonorit 4 exceeded that of a graphite crystal, reaching 5 × 10−5 K at 573 K. The CO2 adsorption onto Sorbonorit 4 gave rise to its contraction at low temperatures and pressures or to its expansion at high temperatures over the entire pressure range. An inversion of the temperature dependence of the adsorption-induced deformation (AID) of Sorbonorit-4 was observed. The AID of Sorbonorit-4 and differential isosteric heat of CO2 adsorption plotted as a function of carbon dioxide uptake varied within the same intervals of adsorption values, reflecting the changes in the state of adsorbed molecules caused by contributions from adsorbate–adsorbent and adsorbate–adsorbate interactions. A simple model of nanoporous carbon adsorbents as randomly oriented nanocrystallites interconnected by a disordered carbon phase is proposed to represent the adsorption- and temperature-induced deformation of nanocrystallites with the macroscopic deformation of the adsorbent granules.
{"title":"In Situ Dilatometry Measurements of Deformation of Microporous Carbon Induced by Temperature and Carbon Dioxide Adsorption under High Pressures","authors":"A. Shkolin, I. Men’shchikov, E. Khozina, A. Fomkin","doi":"10.3390/colloids7020046","DOIUrl":"https://doi.org/10.3390/colloids7020046","url":null,"abstract":"Adsorption-based carbon dioxide capture, utilization, and storage technologies aim to mitigate the accumulation of anthropogenic greenhouse gases that cause climate change. It is assumed that porous carbons as adsorbents are able to demonstrate the effectiveness of these technologies over a wide range of temperatures and pressures. The present study aimed to investigate the temperature-induced changes in the dimensions of the microporous carbon adsorbent Sorbonorit 4, as well as the carbon dioxide adsorption, by using in situ dilatometry. The nonmonotonic changes in the dimensions of Sorbonorit 4 under vacuum were found with increasing temperature from 213 to 573 K. At T > 300 K, the thermal linear expansion coefficient of Sorbonorit 4 exceeded that of a graphite crystal, reaching 5 × 10−5 K at 573 K. The CO2 adsorption onto Sorbonorit 4 gave rise to its contraction at low temperatures and pressures or to its expansion at high temperatures over the entire pressure range. An inversion of the temperature dependence of the adsorption-induced deformation (AID) of Sorbonorit-4 was observed. The AID of Sorbonorit-4 and differential isosteric heat of CO2 adsorption plotted as a function of carbon dioxide uptake varied within the same intervals of adsorption values, reflecting the changes in the state of adsorbed molecules caused by contributions from adsorbate–adsorbent and adsorbate–adsorbate interactions. A simple model of nanoporous carbon adsorbents as randomly oriented nanocrystallites interconnected by a disordered carbon phase is proposed to represent the adsorption- and temperature-induced deformation of nanocrystallites with the macroscopic deformation of the adsorbent granules.","PeriodicalId":10433,"journal":{"name":"Colloids and Interfaces","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43159133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Reiner, Charlotte Schüler, V. Gaukel, H. Karbstein
A lot of applications for (semi-)crystalline triacylglycerol (TAG)-in-water dispersions exist in the life science and pharmaceutical industries. Unfortunately, during storage, these dispersions are often prone to changes in particle size due to unforeseen crystallization and recrystallization events. This results in the alterations of important product properties, such as viscosity and mouthfeel, or the premature release of encapsulated material. In this study, we investigated the effects and interplay of formulation, i.e., emulsifier combination, and processing parameters, i.e., cooling rate, on the colloidal stability of dispersed TAGs and aimed to improve their colloidal stability. We chose phospholipids (PLs) and β-lactoglobulin (β-lg) as the emulsifiers for our model systems, which are commonly applied in many food systems. When dispersions were characterized directly after cooling, we obtained smaller particles and narrower size distributions after fast cooling. Over the course of eleven weeks, the creaming behavior, particle size, melting behavior and polymorphism were characterized. The dispersions stabilized with solely β-lg exhibited a slight increase in particle size, whereas a decrease in size was found when PLs were added. Our results indicate that mass transport phenomena between TAG droplets and particles took place during storage. This migration of TAG molecules changed the composition and size distribution of the dispersed phase, especially at higher PL concentration (0.1 wt%). In our case, this could be prevented by using a lower concentration of PLs, i.e., 0.05 wt%.
{"title":"Effects of Cooling Rate and Emulsifier Combination on the Colloidal Stability of Crystalline Dispersions Stabilized by Phospholipids and β-Lactoglobulin","authors":"J. Reiner, Charlotte Schüler, V. Gaukel, H. Karbstein","doi":"10.3390/colloids7020045","DOIUrl":"https://doi.org/10.3390/colloids7020045","url":null,"abstract":"A lot of applications for (semi-)crystalline triacylglycerol (TAG)-in-water dispersions exist in the life science and pharmaceutical industries. Unfortunately, during storage, these dispersions are often prone to changes in particle size due to unforeseen crystallization and recrystallization events. This results in the alterations of important product properties, such as viscosity and mouthfeel, or the premature release of encapsulated material. In this study, we investigated the effects and interplay of formulation, i.e., emulsifier combination, and processing parameters, i.e., cooling rate, on the colloidal stability of dispersed TAGs and aimed to improve their colloidal stability. We chose phospholipids (PLs) and β-lactoglobulin (β-lg) as the emulsifiers for our model systems, which are commonly applied in many food systems. When dispersions were characterized directly after cooling, we obtained smaller particles and narrower size distributions after fast cooling. Over the course of eleven weeks, the creaming behavior, particle size, melting behavior and polymorphism were characterized. The dispersions stabilized with solely β-lg exhibited a slight increase in particle size, whereas a decrease in size was found when PLs were added. Our results indicate that mass transport phenomena between TAG droplets and particles took place during storage. This migration of TAG molecules changed the composition and size distribution of the dispersed phase, especially at higher PL concentration (0.1 wt%). In our case, this could be prevented by using a lower concentration of PLs, i.e., 0.05 wt%.","PeriodicalId":10433,"journal":{"name":"Colloids and Interfaces","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47528482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Matthieu Fauvel, A. Trybala, D. Tseluiko, V. Starov, H. C. H. Bandulasena
A novel electrophoretic separation technique is presented, where continuous electrophoretic separation is demonstrated using free flowing liquid foams. Continuous foam electrophoresis combines the principle of capillary electrophoresis and interactions between analytes and the electrical double layer, with the ability of Free Flow Electrophoresis to continuously separate and recover analytes automatically. A liquid foam is used to provide a network of deformable micro and nano channels with a high surface area, presenting a novel platform for electrophoresis, where interfacial phenomena could be exploited to modify analyte migration. The main purpose of this paper is to present a proof-of-concept study and provide fundamental understanding of a complex foam system in continuous separation mode, i.e., flowing liquid foam under an external electric field with electrophoresis and chemical reactions at the electrodes continuously changing the system. Liquid foam is generated using a mixture of anionic and non-ionic surfactants and pumped through a microfluidic separation chamber between two electrodes. The effectiveness of the device is demonstrated using a dye mixture containing a neutral dye and an anionic dye. At the outlet, the foam is separated and collected into five fractions which are individually probed for the concentration of the two dyes used. The anionic dye was concentrated up to 1.75 (±0.05) times the initial concentration in a select outlet, while the neutral dye concentration remained unchanged in all outlets, demonstrating the potential for electrophoretic foam separations.
{"title":"Continuous Electrophoretic Separation of Charged Dyes in Liquid Foam","authors":"Matthieu Fauvel, A. Trybala, D. Tseluiko, V. Starov, H. C. H. Bandulasena","doi":"10.3390/colloids7020044","DOIUrl":"https://doi.org/10.3390/colloids7020044","url":null,"abstract":"A novel electrophoretic separation technique is presented, where continuous electrophoretic separation is demonstrated using free flowing liquid foams. Continuous foam electrophoresis combines the principle of capillary electrophoresis and interactions between analytes and the electrical double layer, with the ability of Free Flow Electrophoresis to continuously separate and recover analytes automatically. A liquid foam is used to provide a network of deformable micro and nano channels with a high surface area, presenting a novel platform for electrophoresis, where interfacial phenomena could be exploited to modify analyte migration. The main purpose of this paper is to present a proof-of-concept study and provide fundamental understanding of a complex foam system in continuous separation mode, i.e., flowing liquid foam under an external electric field with electrophoresis and chemical reactions at the electrodes continuously changing the system. Liquid foam is generated using a mixture of anionic and non-ionic surfactants and pumped through a microfluidic separation chamber between two electrodes. The effectiveness of the device is demonstrated using a dye mixture containing a neutral dye and an anionic dye. At the outlet, the foam is separated and collected into five fractions which are individually probed for the concentration of the two dyes used. The anionic dye was concentrated up to 1.75 (±0.05) times the initial concentration in a select outlet, while the neutral dye concentration remained unchanged in all outlets, demonstrating the potential for electrophoretic foam separations.","PeriodicalId":10433,"journal":{"name":"Colloids and Interfaces","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42581639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gabriela Aleksić, T. Cigula, Marina Vukoje, Katarina Itrić Ivanda
In heritage conservation, paper deterioration can be slowed down by controlling the environmental conditions surrounding heritage objects and stabilizing the materials these objects are made of. As conservation materials can also cause optical, chemical, and physical changes in the object, their application should be safe, minimalistic, and purposeful. This paper aimed to observe the functional applications of three biopolymers used in paper conservation. For that purpose, a model paper was coated with methylcellulose (MC), cellulose nanocrystals (CNCs), and wheat starch (WSP) using different wet film deposits. The prepared samples were characterized by determining their physical, optical, and surface properties. The results show that changes in the wet film deposit thickness influenced paper properties. With CNCs, the increase has caused a drastic change of colour properties, with MC hydrophobicity increased and with WSP grammage and thickness increased. All coatings (except CNC24) have contributed to the preservation of the colour properties of the paper from the damage caused by thermal ageing.
{"title":"Influence of Wet Film Thickness on the Functional Applications of Biopolymers in Paper Conservation","authors":"Gabriela Aleksić, T. Cigula, Marina Vukoje, Katarina Itrić Ivanda","doi":"10.3390/colloids7020043","DOIUrl":"https://doi.org/10.3390/colloids7020043","url":null,"abstract":"In heritage conservation, paper deterioration can be slowed down by controlling the environmental conditions surrounding heritage objects and stabilizing the materials these objects are made of. As conservation materials can also cause optical, chemical, and physical changes in the object, their application should be safe, minimalistic, and purposeful. This paper aimed to observe the functional applications of three biopolymers used in paper conservation. For that purpose, a model paper was coated with methylcellulose (MC), cellulose nanocrystals (CNCs), and wheat starch (WSP) using different wet film deposits. The prepared samples were characterized by determining their physical, optical, and surface properties. The results show that changes in the wet film deposit thickness influenced paper properties. With CNCs, the increase has caused a drastic change of colour properties, with MC hydrophobicity increased and with WSP grammage and thickness increased. All coatings (except CNC24) have contributed to the preservation of the colour properties of the paper from the damage caused by thermal ageing.","PeriodicalId":10433,"journal":{"name":"Colloids and Interfaces","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47610302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper describes the use of native β-cyclodextrin (CD) for the modification of silver nanoparticles (AgNPs) in order to improve the determination of the anticancer drug methotrexate (MTX) using surface-enhanced Raman spectroscopy (SERS). A control experiment with unmodified AgNPs showed that the strong SERS signal of MTX can only be achieved in alkaline media. However, competitive interactions and the strong background signal of human body fluid components significantly challenge MTX determination in real samples. While previous reports propose the use of thorough sample pretreatment (e.g., solid phase extraction), the application of CD-modified AgNPs increases the SERS signal of MTX in neutral media by seven times which enables simplifying the analysis and improving its accuracy by reducing the influence of endogenous components of body fluids. A detailed study of the synthesis conditions (CD concentration and reaction time) and SERS registration conditions (pH, NaCl concentration, dilution of urine samples) was performed to maximize the analytical signal and signal-to-noise ratio. The final assay was tested for MTX determination in artificially spiked samples of real human urine. The results demonstrated that MTX can be determined within the concentration range suitable for therapeutic drug monitoring (20–300 μg mL−1) with satisfactory precision (6–15% RSD), accuracy (95–111% apparent recovery), and limit of detection (0.3 μg mL−1).
{"title":"Amplification of SERS Signal of Methotrexate Using Beta-Cyclodextrin Modified Silver Nanoparticles","authors":"N. E. Markina, I. Goryacheva, A. Markin","doi":"10.3390/colloids7020042","DOIUrl":"https://doi.org/10.3390/colloids7020042","url":null,"abstract":"The paper describes the use of native β-cyclodextrin (CD) for the modification of silver nanoparticles (AgNPs) in order to improve the determination of the anticancer drug methotrexate (MTX) using surface-enhanced Raman spectroscopy (SERS). A control experiment with unmodified AgNPs showed that the strong SERS signal of MTX can only be achieved in alkaline media. However, competitive interactions and the strong background signal of human body fluid components significantly challenge MTX determination in real samples. While previous reports propose the use of thorough sample pretreatment (e.g., solid phase extraction), the application of CD-modified AgNPs increases the SERS signal of MTX in neutral media by seven times which enables simplifying the analysis and improving its accuracy by reducing the influence of endogenous components of body fluids. A detailed study of the synthesis conditions (CD concentration and reaction time) and SERS registration conditions (pH, NaCl concentration, dilution of urine samples) was performed to maximize the analytical signal and signal-to-noise ratio. The final assay was tested for MTX determination in artificially spiked samples of real human urine. The results demonstrated that MTX can be determined within the concentration range suitable for therapeutic drug monitoring (20–300 μg mL−1) with satisfactory precision (6–15% RSD), accuracy (95–111% apparent recovery), and limit of detection (0.3 μg mL−1).","PeriodicalId":10433,"journal":{"name":"Colloids and Interfaces","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46869282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Monyake, Taihao Han, D. Ali, L. Alagha, Aditya Kumar
The froth flotation process is extensively used for the selective separation of valuable base metal sulfides from uneconomic associated minerals. However, in this complex multiphase process, various parameters need to be optimized to ensure separation selectivity and peak performance. In this study, two machine learning (ML) models, artificial neural network (ANN) and random forests (RF), were used to predict the efficiency of in-house synthesized chitosan-polyacrylamide copolymers (C-PAMs) in the depression of iron sulfide minerals (i.e., pyrite) while valuable base metal sulfides (i.e., galena and chalcopyrite) were floated using nine flotation variables as inputs to the models. The prediction performance of the models was rigorously evaluated based on the coefficient of determination (R2) and the root-mean-square error (RMSE). The results showed that the RF model was able to produce high-fidelity predictions of the depression of pyrite once thoroughly trained as compared to ANN. With the RF model, the overall R2 and RMSE values were 0.88 and 4.38 for the training phase, respectively, and R2 of 0.90 and RMSE of 3.78 for the testing phase. As for the ANN, during the training phase, the overall R2 and RMSE were 0.76 and 4.75, respectively, and during the testing phase, the R2 and RMSE were 0.65 and 5.42, respectively. Additionally, fundamental investigations on the surface chemistry of C-PAMs at the mineral–water interface were conducted to give fundamental insights into the behavior of different metal sulfides during the flotation process. C-PAM was found to strongly adsorb on pyrite as compared to galena and chalcopyrite through zeta potential, X-ray photoelectron spectroscopy (XPS), and adsorption density measurements. XPS tests suggested that the adsorption mechanism of C-PAM on pyrite was through chemisorption of the amine and amide groups of the polymer.
{"title":"Experimental and Machine Learning Studies on Chitosan-Polyacrylamide Copolymers for Selective Separation of Metal Sulfides in the Froth Flotation Process","authors":"K. Monyake, Taihao Han, D. Ali, L. Alagha, Aditya Kumar","doi":"10.3390/colloids7020041","DOIUrl":"https://doi.org/10.3390/colloids7020041","url":null,"abstract":"The froth flotation process is extensively used for the selective separation of valuable base metal sulfides from uneconomic associated minerals. However, in this complex multiphase process, various parameters need to be optimized to ensure separation selectivity and peak performance. In this study, two machine learning (ML) models, artificial neural network (ANN) and random forests (RF), were used to predict the efficiency of in-house synthesized chitosan-polyacrylamide copolymers (C-PAMs) in the depression of iron sulfide minerals (i.e., pyrite) while valuable base metal sulfides (i.e., galena and chalcopyrite) were floated using nine flotation variables as inputs to the models. The prediction performance of the models was rigorously evaluated based on the coefficient of determination (R2) and the root-mean-square error (RMSE). The results showed that the RF model was able to produce high-fidelity predictions of the depression of pyrite once thoroughly trained as compared to ANN. With the RF model, the overall R2 and RMSE values were 0.88 and 4.38 for the training phase, respectively, and R2 of 0.90 and RMSE of 3.78 for the testing phase. As for the ANN, during the training phase, the overall R2 and RMSE were 0.76 and 4.75, respectively, and during the testing phase, the R2 and RMSE were 0.65 and 5.42, respectively. Additionally, fundamental investigations on the surface chemistry of C-PAMs at the mineral–water interface were conducted to give fundamental insights into the behavior of different metal sulfides during the flotation process. C-PAM was found to strongly adsorb on pyrite as compared to galena and chalcopyrite through zeta potential, X-ray photoelectron spectroscopy (XPS), and adsorption density measurements. XPS tests suggested that the adsorption mechanism of C-PAM on pyrite was through chemisorption of the amine and amide groups of the polymer.","PeriodicalId":10433,"journal":{"name":"Colloids and Interfaces","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43903120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Coarse-grained molecular dynamics simulations that incorporate explicit water-mediated hydrophilic/hydrophobic interactions are employed to track spatiotemporal evolution of diblock copolymer aggregation in initially homogeneous solutions. A phase portrait of the observed morphologies and their quantitative geometric features such as aggregation numbers, packing parameters, and radial distribution functions of solvent/monomers are presented. Energetic and entropic measures relevant to self-assembly such as specific solvent accessible surface area (SASA) and probability distribution functions (pdfs) of segmental stretch of copolymer chains are analyzed. The simulations qualitatively capture experimentally observed morphological diversity in diblock copolymer solutions. Topologically simpler structures predicted include spherical micelles, vesicles (polymersomes), lamellae (bilayers), linear wormlike micelles, and tori. More complex morphologies observed for larger chain lengths and nearly symmetric copolymer compositions include branched wormlike micelles with Y-shaped junctions and cylindrical micelle networks. For larger concentrations, vesicle strands, held together by hydrogen bonds, and “giant” composite aggregates that consist of lamellar, mixed hydrophobic/hydrophilic regions and percolating water cores are predicted. All structures are dynamic and exhibit diffuse domain boundaries. Morphology transitions across topologically simpler structures can be rationalized based on specific SASA measurements. PDFs of segmental stretch within vesicular assemblies appear to follow a log-normal distribution conducive for maximizing configuration entropy.
{"title":"Morphological Diversity in Diblock Copolymer Solutions: A Molecular Dynamics Study","authors":"Senyuan Liu, R. Sureshkumar","doi":"10.3390/colloids7020040","DOIUrl":"https://doi.org/10.3390/colloids7020040","url":null,"abstract":"Coarse-grained molecular dynamics simulations that incorporate explicit water-mediated hydrophilic/hydrophobic interactions are employed to track spatiotemporal evolution of diblock copolymer aggregation in initially homogeneous solutions. A phase portrait of the observed morphologies and their quantitative geometric features such as aggregation numbers, packing parameters, and radial distribution functions of solvent/monomers are presented. Energetic and entropic measures relevant to self-assembly such as specific solvent accessible surface area (SASA) and probability distribution functions (pdfs) of segmental stretch of copolymer chains are analyzed. The simulations qualitatively capture experimentally observed morphological diversity in diblock copolymer solutions. Topologically simpler structures predicted include spherical micelles, vesicles (polymersomes), lamellae (bilayers), linear wormlike micelles, and tori. More complex morphologies observed for larger chain lengths and nearly symmetric copolymer compositions include branched wormlike micelles with Y-shaped junctions and cylindrical micelle networks. For larger concentrations, vesicle strands, held together by hydrogen bonds, and “giant” composite aggregates that consist of lamellar, mixed hydrophobic/hydrophilic regions and percolating water cores are predicted. All structures are dynamic and exhibit diffuse domain boundaries. Morphology transitions across topologically simpler structures can be rationalized based on specific SASA measurements. PDFs of segmental stretch within vesicular assemblies appear to follow a log-normal distribution conducive for maximizing configuration entropy.","PeriodicalId":10433,"journal":{"name":"Colloids and Interfaces","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47135847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A detailed statistical description of the evolution of supersaturated-by-gas solution at degassing has been presented on the basis of finding the time-dependent distribution in radii of overcritical gas bubbles. The influence of solution viscosity and capillarity via internal pressure in the bubbles on this distribution has been considered until the moment when the gas supersaturation drops due to depletion and stops nucleation of new overcritical gas bubbles. This study aims to find the nonstationary growth rate of overcritical bubbles depending on gas supersaturation, diffusivity and solubility in solution, solution viscosity, and surface tension on bubble surface. Other important factors are linked with the initial rate of homogeneous gas bubble nucleation and coupling between diffusivity and viscosity in the solution. Here, we numerically studied how all these factors affect the time-dependent distribution function of overcritical bubbles in their radii, maximal and mean bubble radii, and the time-dependent swelling ratio of a supersaturated-by-gas solution in a wide range of solution viscosities.
{"title":"The Effects of Viscosity and Capillarity on Nonequilibrium Distribution of Gas Bubbles in Swelling Liquid–Gas Solution","authors":"A. Shchekin, A. Kuchma, E. Aksenova","doi":"10.3390/colloids7020039","DOIUrl":"https://doi.org/10.3390/colloids7020039","url":null,"abstract":"A detailed statistical description of the evolution of supersaturated-by-gas solution at degassing has been presented on the basis of finding the time-dependent distribution in radii of overcritical gas bubbles. The influence of solution viscosity and capillarity via internal pressure in the bubbles on this distribution has been considered until the moment when the gas supersaturation drops due to depletion and stops nucleation of new overcritical gas bubbles. This study aims to find the nonstationary growth rate of overcritical bubbles depending on gas supersaturation, diffusivity and solubility in solution, solution viscosity, and surface tension on bubble surface. Other important factors are linked with the initial rate of homogeneous gas bubble nucleation and coupling between diffusivity and viscosity in the solution. Here, we numerically studied how all these factors affect the time-dependent distribution function of overcritical bubbles in their radii, maximal and mean bubble radii, and the time-dependent swelling ratio of a supersaturated-by-gas solution in a wide range of solution viscosities.","PeriodicalId":10433,"journal":{"name":"Colloids and Interfaces","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46821900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wellington Tafireyi, Max Littlewood, H. C. H. Bandulasena, A. Trybala, V. Starov
The wetting behavior of droplets of aqueous surfactant solutions over hydrophobic thin PVDF porous membrane and non-porous hydrophobic PVDF film is investigated for small (~10 μL) droplets of aqueous trisiloxane surfactant solutions: superspreader S 240. The time dependencies of contact angle, droplet radius, wetted area and volume were monitored as well as penetration into the porous substrate. It is shown that the fast spreading of droplets of trisiloxane solutions takes place both in the case of porous and non-porous substrates at a concentration above some critical concentration. It was found that the trisiloxane droplets penetrate into the hydrophobic porous substrates and disappear much faster than on a corresponding hydrophobic non-porous substrate, which was not observed before. This phenomenon is referred to as “superpenetration”.
{"title":"Superspreading Surfactant on Hydrophobic Porous Substrates","authors":"Wellington Tafireyi, Max Littlewood, H. C. H. Bandulasena, A. Trybala, V. Starov","doi":"10.3390/colloids7020038","DOIUrl":"https://doi.org/10.3390/colloids7020038","url":null,"abstract":"The wetting behavior of droplets of aqueous surfactant solutions over hydrophobic thin PVDF porous membrane and non-porous hydrophobic PVDF film is investigated for small (~10 μL) droplets of aqueous trisiloxane surfactant solutions: superspreader S 240. The time dependencies of contact angle, droplet radius, wetted area and volume were monitored as well as penetration into the porous substrate. It is shown that the fast spreading of droplets of trisiloxane solutions takes place both in the case of porous and non-porous substrates at a concentration above some critical concentration. It was found that the trisiloxane droplets penetrate into the hydrophobic porous substrates and disappear much faster than on a corresponding hydrophobic non-porous substrate, which was not observed before. This phenomenon is referred to as “superpenetration”.","PeriodicalId":10433,"journal":{"name":"Colloids and Interfaces","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41360735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The rheology of oil-in-water (O/W) emulsions, stabilized and thickened by cellulose nanocrystals, also referred to as nanocrystalline cellulose (NCC), was investigated over broad ranges of NCC and oil concentrations. The NCC concentration was varied from 1.03 to 7.41 wt% based on the aqueous phase. The oil concentration of the emulsion was varied from approximately 10 to 70 wt%. The emulsions produced were highly stable with respect to creaming and coalescence. The emulsions were non-Newtonian in that they exhibited strong shear-thinning behavior. The rheological data were described adequately by a power-law model. The consistency index (K) and the flow behavior index (n) of the emulsions were strongly dependent on the NCC and oil concentrations. At a fixed oil concentration, the consistency index increased whereas the flow behavior index decreased with the increase in NCC concentration. A similar behavior was observed when the NCC concentration was fixed and the oil concentration was increased; that is, the consistency index increased whereas the flow behavior index decreased.
{"title":"Rheology of Pickering Emulsions Stabilized and Thickened by Cellulose Nanocrystals over Broad Ranges of Oil and Nanocrystal Concentrations","authors":"Saumay Kinra, R. Pal","doi":"10.3390/colloids7020036","DOIUrl":"https://doi.org/10.3390/colloids7020036","url":null,"abstract":"The rheology of oil-in-water (O/W) emulsions, stabilized and thickened by cellulose nanocrystals, also referred to as nanocrystalline cellulose (NCC), was investigated over broad ranges of NCC and oil concentrations. The NCC concentration was varied from 1.03 to 7.41 wt% based on the aqueous phase. The oil concentration of the emulsion was varied from approximately 10 to 70 wt%. The emulsions produced were highly stable with respect to creaming and coalescence. The emulsions were non-Newtonian in that they exhibited strong shear-thinning behavior. The rheological data were described adequately by a power-law model. The consistency index (K) and the flow behavior index (n) of the emulsions were strongly dependent on the NCC and oil concentrations. At a fixed oil concentration, the consistency index increased whereas the flow behavior index decreased with the increase in NCC concentration. A similar behavior was observed when the NCC concentration was fixed and the oil concentration was increased; that is, the consistency index increased whereas the flow behavior index decreased.","PeriodicalId":10433,"journal":{"name":"Colloids and Interfaces","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43690599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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