Colloids and Interfaces

19 pages, 3615 KiB

Open AccessArticle

Caffeine Adsorption on a Thermally Modified Bentonite: Adsorbent Characterization, Experimental Design, Equilibrium and Kinetics

by Javier A. Quintero-Jaramillo, Javier Ignacio Carrero and Nancy R. Sanabria-González

Colloids Interfaces 2024, 8(2), 26; https://doi.org/10.3390/colloids8020026 - 15 Apr 2024

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Abstract

Caffeine is a chemical compound found in various products such as coffee, tea, and energy drinks; therefore, it is common in wastewater and surface water. The present study investigated caffeine adsorption on a thermally modified bentonite-type clay. The effects of the heat treatment [...] Read more.

Caffeine is a chemical compound found in various products such as coffee, tea, and energy drinks; therefore, it is common in wastewater and surface water. The present study investigated caffeine adsorption on a thermally modified bentonite-type clay. The effects of the heat treatment of the adsorbent over the temperature range of 60–500 °C, as well as the initial pH of the solution, stirring speed, and contact time, on the removal of caffeine were analyzed. The adsorbent was characterized by XRF, XRD, FT–IR, thermal analysis (TGA–DSC), and N₂ physisorption at 77 K. The response surface methodology (RSM) based on a central composite design (CCD) was used to evaluate and optimize the adsorption of caffeine in aqueous solution. The maximum adsorption capacity of caffeine obtained with the Langmuir model was 80.3 ± 2.1 mg/g (0.41 ± 0.01 mmol/g) at 25 °C under equilibrium conditions (initial pH = 8.0, stirring speed = 400 rpm, contact time = 120 min). A kinetic study showed that the pseudo-second-order and Elovich models adequately describe the adsorption process. Bentonite thermally modified at 400 °C can be considered a low-cost adsorbent with potential application for removing caffeine in aqueous media. Full article

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16 pages, 5011 KiB

Open AccessArticle

Adsorption Layer Properties and Foam Behavior of Aqueous Solutions of Whey Protein Isolate (WPI) Modified by Vacuum Cold Plasma (VCP)

by Elham Ommat Mohammadi, Samira Yeganehzad, Mohammad Ali Hesarinejad, Mohsen Dabestani, Regine von Klitzing, Reinhard Miller and Emanuel Schneck

Colloids Interfaces 2024, 8(2), 25; https://doi.org/10.3390/colloids8020025 - 09 Apr 2024

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Abstract

For years, cold plasma processing has been used as a non-thermal technology in industries such as food. As interfacial properties of protein play a remarkable role in many processes, this study investigates the effect of cold plasma on the foaming and interfacial behavior [...] Read more.

For years, cold plasma processing has been used as a non-thermal technology in industries such as food. As interfacial properties of protein play a remarkable role in many processes, this study investigates the effect of cold plasma on the foaming and interfacial behavior of WPI. The objective of this study is to evaluate the effect of different gases (air, 1:1 argon–air mixture, and sulfur hexafluoride (SF6)) used in low-pressure cold plasma (VCP) treatments of whey protein isolate (WPI) on the surface and foaming behavior of aqueous WPI solutions. Dynamic surface dilational elasticity, surface tension isotherms, surface layer thickness, and the foamability and foam stability were investigated in this study. VCP treatment did not significantly affect the adsorption layer thickness. However, an increase in induction time, surface pressure equilibrium value, and aggregated size is observed after SF₆VCP treatment, which can be attributed to the reaction of WPI with the reactive SF₆ species of the cold plasma. The surface dilational elastic modulus increased after VCP treatment, which can be related to the increased mechanical strength of the protein layer via sulfonation and aggregate formation. VCP treatment of WPI increases the foam stability, while the average diameter of foam bubbles and liquid drainage in the foam depends on the gas used for the cold plasma. Full article

(This article belongs to the Special Issue Proteins at the Interface)

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18 pages, 3864 KiB

Open AccessArticle

In Vitro Gastrointestinal Release of Chlorogenic Acid and Curcumin Co-Encapsulated in Double Emulsions with the Outer Interface Stabilized by Cellulose Nanocrystals

by Javier Paredes-Toledo, Javier Herrera, Paulo Díaz-Calderón, Paz Robert and Begoña Giménez

Colloids Interfaces 2024, 8(2), 24; https://doi.org/10.3390/colloids8020024 - 09 Apr 2024

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Abstract

A Pickering double emulsion (DE) with an outer (O:W₂) interface stabilized by cellulose nanocrystals (DE-CNC) was designed as a co-delivery systems for chlorogenic acid (CA) and curcumin, then compared with a control DE emulsion with an O:W₂ interface stabilized with [...] Read more.

A Pickering double emulsion (DE) with an outer (O:W₂) interface stabilized by cellulose nanocrystals (DE-CNC) was designed as a co-delivery systems for chlorogenic acid (CA) and curcumin, then compared with a control DE emulsion with an O:W₂ interface stabilized with sodium caseinate (DE-NaCas). DE-CNC was more resistant to creaming during storage (6.79%, day 42) and showed higher encapsulation efficiency (EE) of CA (>90%). Conversely, both DEs exhibited similarly high EE for curcumin (>97%). The ζ-potential values were highly negative in both DEs, but tended to be lower in DE-CNC due to the highly negative charge of the CNCs. DE-CNC allowed for a steady release of CA during the oral, gastric, and intestinal phases of digestion, while a total release of CA was already observed in the gastric phase in case of DE-NaCas. The bioaccessibility of CA was similar in both DEs (~57–58%). Curcumin was mainly released in the intestinal phase with both DEs, reaching slightly lower bioaccessibility values with DE-CNC. The use of CNCs as a stabilizer for the outer interface of DEs is a promising strategy to increase the stability and EE of these systems, providing oral co-delivery vehicles capable of releasing significantly bioactive compounds during the intestinal phase of digestion. Full article

(This article belongs to the Special Issue Recent Advances on Emulsions and Applications: Volume II)

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22 pages, 5203 KiB

Open AccessArticle

Oil/Brine Screening for Improved Fluid/Fluid Interactions during Low-Salinity Water Flooding

by Jose Villero-Mandon, Peyman Pourafshary and Masoud Riazi

Colloids Interfaces 2024, 8(2), 23; https://doi.org/10.3390/colloids8020023 - 01 Apr 2024

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Abstract

Low-salinity water flooding/smart water flooding (LSWF/SWF) are used for enhanced oil recovery (EOR) because of the improved extraction efficiency. These methods are more environmentally friendly and in many scenarios more economical for oil recovery. They are proven to increase recovery factors (RFs) by [...] Read more.

Low-salinity water flooding/smart water flooding (LSWF/SWF) are used for enhanced oil recovery (EOR) because of the improved extraction efficiency. These methods are more environmentally friendly and in many scenarios more economical for oil recovery. They are proven to increase recovery factors (RFs) by between 6 and 20%, making LSWF/SWF technologies that should be further evaluated to replace conventional water flooding or other EOR methods. Fluid/fluid interaction improvements include interfacial tension (IFT) reduction, viscoelastic behavior (elastic properties modification), and microemulsion generation, which could complement the main mechanisms, such as wettability alteration. In this research, we evaluate the importance of fluid/fluid mechanisms during LSWF/SWF operations. Our study showed that a substantial decrease in IFT occurs when the oil asphaltene content is in the range of 0% to 3 wt.%. An IFT reduction was observed at low salinity (0–10,000 ppm) and a specific oil composition condition. Optimal IFT occurs at higher divalent ion concentrations when oil has low asphaltene content. For the oil with high asphaltene content, the sulfates concentration controls the IFT alteration. At high asphaltene concentrations, the formation of micro-dispersion is not effective to recover oil, and only a 5% recovery factor improvement was observed. The presence of asphaltene at the oil/low-salinity brine interface increases the energy required to disrupt it, inducing significant changes in the elastic moduli. In cases of low asphaltene content, the storage modulus demonstrates optimal performance at higher divalent concentrations. Conversely, at high asphaltene concentrations, the dominant factors to control the interface are paraffin content and temperature. Full article

(This article belongs to the Special Issue Crude Oil Recovery)

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20 pages, 4026 KiB

Open AccessArticle

Shrimp Oil-Enriched Mayonnaise Prepared Using Fish Myofibrillar Protein as a Substitute for Egg Yolk: Physical, Rheological, and Sensory Properties

by Bharathipriya Rajasekaran, Avtar Singh, Bin Zhang, Hui Hong, Thummanoon Prodpran and Soottawat Benjakul

Colloids Interfaces 2024, 8(2), 22; https://doi.org/10.3390/colloids8020022 - 18 Mar 2024

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Abstract

The effect of SO (shrimp oil) at various levels (5, 10, and 15%) on the stability of mayonnaise was investigated. Droplet size (d₃₂ and d₄₃), polydispersity index, and microstructure results showed an upsurge in droplet sizes with augmenting level of [...] Read more.

The effect of SO (shrimp oil) at various levels (5, 10, and 15%) on the stability of mayonnaise was investigated. Droplet size (d₃₂ and d₄₃), polydispersity index, and microstructure results showed an upsurge in droplet sizes with augmenting level of SO in mayonnaise (5 to 15%) (p < 0.05). SO imparted a bright orange color to the mayonnaise as evidenced by increased a* and b* values with lower L* values (p < 0.05). Moreover, the impact of a fish myofibrillar protein (FMP) substitution for egg yolk (0, 25, 50, 75%) in mayonnaise containing SO (5% and 10%) was also studied. Increasing the level of FMP substitution in SO-added mayonnaise showed a dilution effect and reduced a* and b* values (p < 0.05). In addition, excessive FMP substitution up to 75% drastically increased centrifugal and thermal creaming indices, indicating lowered stability (p < 0.05). Nevertheless, with the augmenting FMP substitutions, the viscosity, texture, and rheological properties in mayonnaise became lower (p < 0.05). However, there were no differences in overall acceptability scores between 5% SO-added mayonnaise with 25% FMP substitution (SO5:FMP25) and 5% SO-added mayonnaise without FMP substitution (SO5:FMP0) (p > 0.05). A confocal laser scanning microscopic (CLSM) study revealed a smaller droplet and less aggregation in the SO5:FMP0 sample, compared to SO5:FMP25. The incorporation of SO and FMP substitution yielded the resulting mayonnaise, which met the requirements of a healthy food since SO is rich in PUFA and the replacement of egg yolk by FMP can contribute several health benefits. The incorporation of SO as well as FMP as substitution for egg yolk therefore has potential in the development of functional foods. Full article

(This article belongs to the Special Issue Food Colloids II)

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13 pages, 2488 KiB

Open AccessArticle

Theoretical and Experimental Determinations of the Hydrophilic–Lipophilic Balance (HLB) of Representative Oils and Lecithins

by Gary Smejkal, Vera Gross and Alexander Lazarev

Colloids Interfaces 2024, 8(2), 21; https://doi.org/10.3390/colloids8020021 - 16 Mar 2024

Viewed by 1318

Abstract

The hydrophilic–lipophilic balance (HLB) is a valuable parameter used to determine the relative hydrophobicity of a compound based on its chemical structure. This semi-empirical parameter has been instrumental in formulating oil-in-water and water-in-oil emulsions using well-characterized ingredients with known HLB values. However, recent [...] Read more.

The hydrophilic–lipophilic balance (HLB) is a valuable parameter used to determine the relative hydrophobicity of a compound based on its chemical structure. This semi-empirical parameter has been instrumental in formulating oil-in-water and water-in-oil emulsions using well-characterized ingredients with known HLB values. However, recent trends toward the use of minimally processed “virgin” oils of therapeutic or nutritional value may render the reported “required HLB” values inaccurate. Minimally processed oils can contain numerous compounds at varying or unknown concentrations, rendering the HLB value incalculable. Factors such as regional source, growing season, and processing method contribute to the variability in oil composition. Furthermore, the solubilization of lipophilic bioactives in oils can significantly alter the HLB of the oil phase in a concentration-dependent manner. This complicates the formulation of emulsions, as the HLB values of both the oil phase and emulsifiers must be closely matched to achieve stable formulations. This study presents a simple and efficient experimental method to determine an HLB value of a complex ingredient without resorting to lengthy Design-of-Experiment (DoE) matrices and trial-and-error approaches. The optimal HLB of a formulation can be determined from a series of experiments in which two well-characterized surfactants of known HLB values are mixed at varying proportions with an unknown oil phase, where the HLB of the oil is considered to match the HLB value of the surfactants combined at the proportion at which nanoemulsions with the smallest, most stable oil droplets are formed. Similarly, when the HLB values of the oil phase and other contributing components are precisely known, the unknown HLB of a complex natural surfactant can be calculated. These calculations assist in formulating emulsions efficiently and effectively by ensuring optimal compatibility among all the components. Full article

(This article belongs to the Special Issue Recent Advances on Emulsions and Applications: Volume II)

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12 pages, 2777 KiB

Open AccessArticle

Start-Up Rotation of a Porous Colloidal Sphere in a Cavity

by Chan W. Yu and Huan J. Keh

Colloids Interfaces 2024, 8(2), 20; https://doi.org/10.3390/colloids8020020 - 11 Mar 2024

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Abstract

The starting rotation of a porous sphere induced by the sudden application of a continuous torque about its diameter at the center of a spherical cavity filled with an incompressible Newtonian fluid at low Reynolds numbers is analyzed. The unsteady Stokes and Brinkman [...] Read more.

The starting rotation of a porous sphere induced by the sudden application of a continuous torque about its diameter at the center of a spherical cavity filled with an incompressible Newtonian fluid at low Reynolds numbers is analyzed. The unsteady Stokes and Brinkman equations governing the fluid velocities outside and inside the porous particle, respectively, are solved via the Laplace transform, and an explicit formula of its dynamic angular velocity as a function of the pertinent parameters is obtained. The behavior of the start-up rotation of an isolated porous particle and the cavity wall effect on the particle rotation are interesting. The angular velocity of the particle grows incessantly over time from an initial zero to its final value, while the angular acceleration declines with time continuously. In general, the transient angular velocity is an increasing function of the porosity of the particle. A porous sphere with higher fluid permeability rotates at higher angular velocity and acceleration relative to the reference particle at any elapsed time but lags behind the reference particle in the percentage growth of angular velocity towards the respective terminal values. The transient angular velocity decreases with increasing particle-to-cavity radius ratio, but it is not a sensitive function of the radius ratio when the resistance to fluid flow inside the porous particle or the radius ratio itself is small. Full article

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13 pages, 2852 KiB

Open AccessArticle

Dynamic Interfacial Properties and Foamability of DoTAB/SiO₂ Mixtures

by Fariza Amankeldi, Maratbek Gabdullin, Miras Issakhov, Zhanar Ospanova, Altynay Sharipova, Saule Aidarova and Reinhard Miller

Colloids Interfaces 2024, 8(2), 19; https://doi.org/10.3390/colloids8020019 - 11 Mar 2024

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Abstract

The interaction between nanoparticles and cationic surfactants is an exciting and emerging field in interfacial science. This area of research holds significant promise, linking fundamental principles to practical applications in a variety of industries, including chemical processes, biomedical applications and the petroleum industry. [...] Read more.

The interaction between nanoparticles and cationic surfactants is an exciting and emerging field in interfacial science. This area of research holds significant promise, linking fundamental principles to practical applications in a variety of industries, including chemical processes, biomedical applications and the petroleum industry. This study explores the interaction between dodecyltrimethylammonium bromide (DoTAB) and silica (SiO₂) nanoparticles, investigating their influence on dynamic interfacial properties and foam characteristics. Through equilibrium and dynamic surface tension measurements, along with examining the dilational visco-elasticity behavior, this research reveals the complex surface behavior of DoTAB/SiO₂ mixtures compared to individual surfactant solutions. The foamability and stability experiments indicate that the addition of SiO₂ significantly improves the foam stability. Notably, stable foams are achieved at low SiO₂ concentrations, suggesting a cost-effective approach to enhancing the foam stability. This study identifies the optimal stability conditions for 12 mM DoTAB solutions, emphasizing the crucial role of the critical aggregation concentration region. These findings offer valuable insights for designing surfactant-nanoparticle formulations to enhance foam performance in various industrial applications. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of Colloids and Interfaces 2024)

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13 pages, 2569 KiB

Open AccessArticle

The Synthesis and Reactivity of Mesoporous and Surface-Rough Vinyl-Containing ORMOSIL Nanoparticles

by Nathan I. Walton, Eric M. Brozek, Courtney C. Gwinn and Ilya Zharov

Colloids Interfaces 2024, 8(2), 18; https://doi.org/10.3390/colloids8020018 - 07 Mar 2024

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Abstract

Silica nanoparticles synthesized solely from organosilanes naturally possess a greater number of organic functionalities than silica nanoparticles surface-modified with organosilanes. We report the synthesis of organically modified silica (ORMOSIL) nanoparticles with a mesoporous and surface-rough morphology and with a high surface area, made [...] Read more.

Silica nanoparticles synthesized solely from organosilanes naturally possess a greater number of organic functionalities than silica nanoparticles surface-modified with organosilanes. We report the synthesis of organically modified silica (ORMOSIL) nanoparticles with a mesoporous and surface-rough morphology and with a high surface area, made solely from vinyltrimethoxy silane. We chemically modified these vinyl silica nanoparticles using bromination and hydroboration, and demonstrated the high accessibility and reactivity of the vinyl groups with an ~85% conversion of the functional groups for the bromination of both particle types, a ~60% conversion of the functional groups for the hydroboration of surface-rough particles and a 90% conversion of the functional groups for the hydroboration of mesoporous particles. We determined that the mesoporous vinyl silica nanoparticles, while having a surface area that lies between the non-porous and surface-rough vinyl silica nanoparticles, provide the greatest accessibility to the vinyl groups for boronation and allow for the incorporating of up to 3.1 × 10⁶ B atoms per particle, making the resulting materials attractive for boron neutron capture therapy. Full article

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14 pages, 3951 KiB

Open AccessArticle

Influence of Surface Roughness on Interfacial Properties of Particle Networks

by Elton L. Correia, Nick Brown, Dimitrios V. Papavassiliou and Sepideh Razavi

Colloids Interfaces 2024, 8(2), 17; https://doi.org/10.3390/colloids8020017 - 04 Mar 2024

Viewed by 960

Abstract

The behavior of colloidal particles near fluid interfaces has attracted significant scientific interest, as particles minimize the contact area between the two fluid phases, stabilizing interfacial systems. This study explores the influence of surface roughness on the properties of particle monolayers at the [...] Read more.

The behavior of colloidal particles near fluid interfaces has attracted significant scientific interest, as particles minimize the contact area between the two fluid phases, stabilizing interfacial systems. This study explores the influence of surface roughness on the properties of particle monolayers at the air–water interface, focusing on colloidal silica particles and fumed silica particles of similar hydrodynamic diameter. This research involves comparing low-surface-area (LSA) and medium-surface-area (MSA) fumed silica particles with spherical colloidal silica particles (250 nm in diameter). Utilizing a Langmuir trough, the interfacial particle networks are compressed and expanded. Analysis of surface pressure isotherms reveals that fumed silica particle monolayers form networks at a lower particle surface coverage compared to spherical particles. The spherical particle monolayer exhibits a higher apparent surface elasticity, indicating greater resistance to the applied compression compared to fumed silica networks. Additionally, monolayers formed by fumed silica particles display hysteresis even after successive compressions and expansions due to irreversible particle interlocking and the formation of multilayered aggregates. These findings provide insights into the impact of surface roughness on the behavior of particle monolayers at fluid interfaces, offering valuable information for designing and optimizing mechanisms involved in emulsion and foam stabilization. Full article

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19 pages, 3266 KiB

Open AccessFeature PaperArticle

Ionic Strength Effect in the Equilibrium and Rheological Behavior of an Amphiphilic Triblock Copolymer at the Air/Solution Interface

by Carlo Carbone, Eduardo Guzmán, Julia Maldonado-Valderrama, Ramón G. Rubio and Francisco Ortega

Colloids Interfaces 2024, 8(2), 16; https://doi.org/10.3390/colloids8020016 - 01 Mar 2024

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Abstract

This study investigates the effect of an inert salt (NaCl) on the equilibrium interfacial tension and dilatational modulus of Pluronic F-68 copolymer, a triblock copolymer consisting of two terminal blocks of poly(ethylene oxide) and a less hydrophilic central block of poly(propylene oxide). Interfacial [...] Read more.

This study investigates the effect of an inert salt (NaCl) on the equilibrium interfacial tension and dilatational modulus of Pluronic F-68 copolymer, a triblock copolymer consisting of two terminal blocks of poly(ethylene oxide) and a less hydrophilic central block of poly(propylene oxide). Interfacial tension measurements were carried out using a surface force balance and a drop shape tensiometer, while rheological measurements were carried out in two different frequency ranges. This involved the use of the oscillatory barrier/droplet method and electrocapillary wave measurements, complemented by an appropriate theoretical framework. This work aimed to elucidate the influence of NaCl on the interfacial behavior of Gibbs monolayers of Pluronic F-68. In addition, this study highlights some of the technical and theoretical limitations associated with obtaining reliable dilatational rheological data at high frequencies (<1 kHz) using electrocapillary wave measurements. The results provide valuable insights into the interplay between salt presence and interfacial properties of Pluronic F-68 and highlight the challenges of obtaining accurate dilatational rheological data under specific measurement conditions. Full article

(This article belongs to the Special Issue B&D 2023)

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1 pages, 142 KiB

Open AccessCorrection

Correction: Veronico et al. Enhancing Oil-Uptake Efficiency with an Alkyl Polyglycoside–Dodecanol Formulation. Colloids Interfaces 2024, 8, 6

by Lorenzo Veronico, Giuseppe Colafemmina and Luigi Gentile

Colloids Interfaces 2024, 8(2), 15; https://doi.org/10.3390/colloids8020015 - 29 Feb 2024

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Abstract

In the original publication [...] Full article

(This article belongs to the Special Issue Progress in Surfactants with Low Environmental Impact)

9 pages, 2178 KiB

Open AccessArticle

A New Method for Calculating the Hamaker Constant Based on the Hansen Solubility Parameters for Non-Polar Liquids

by Hiroyuki Ohshima and Shin-ichi Takeda

Colloids Interfaces 2024, 8(2), 14; https://doi.org/10.3390/colloids8020014 - 22 Feb 2024

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Abstract

A simple relationship between the Hamaker constant and the Hansen solubility parameters for non-polar liquids is derived by combining a Hamaker constant/surface tension relationship derived by Israelachvili and a Hansen solubility parameters/surface tension relationship derived by Abbott. With this relationship, one can easily [...] Read more.

A simple relationship between the Hamaker constant and the Hansen solubility parameters for non-polar liquids is derived by combining a Hamaker constant/surface tension relationship derived by Israelachvili and a Hansen solubility parameters/surface tension relationship derived by Abbott. With this relationship, one can easily estimate the Hamaker constant of non-polar liquids on the basis of the database of the Hansen solubility parameters. This is an entirely new method for calculating the Hamaker constant without recourse to data on the frequency-dependent dielectric permittivity of those substances (which are required for the rigorous Lifshitz theory) and laborious numerical calculations. Full article

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Colloids Interfaces, Volume 8, Issue 2 (April 2024) – 13 articles

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