Synergistic and Competitive Adsorption of Hydrophilic Nanoparticles and Oil-Soluble Surfactants at the Oil–Water Interface (original) (raw)
Related papers
Properties of Fatty Amine–Silica Nanoparticle Interfacial Layers at the Hexane–Water Interface
The Journal of Physical Chemistry C, 2012
The formation and properties of composite layers of silica nanoparticles and an oil-soluble (fatty) amine surfactant at the oil−water interface have been studied using interfacial tensiometry, rheology, and contact angle measurements to characterize the synergy between the particles and surfactant. The initially hydrophilic particles interact with the surfactant only at the water−hexane interface. Synergistic interactions are required for interface stabilization. A key result is that nanoparticle attachment is driven by surfactant adsorption at the liquid interface. Particles are efficiently bound to the interface once the adsorbed surfactant layer is close to saturation. Surfactant adsorption onto the particle surfaces optimizes the particle wettability and promotes particle aggregation into networks that enhance the viscoelasticity of the interface. The implications of these results for controlling the formation and kinetic stability of emulsions containing particles and surfactant are discussed.
Langmuir, 2007
Charge-stabilized dispersions of inorganic colloids are shown to induce spontaneous emulsification of hydrophobic (TPM) molecules to stable oil-in-water emulsions, with monodisperse, mesoscopic oil droplet diameters in the range of 30-150 nm, irrespective of the polydispersity of the starting dispersions. The results for cobalt ferrite particles and commercial silica sols extend our first study (Sacanna, S.; Kegel, W. K.; Philipse, A. Phys. ReV. Lett. 2007, 98, 158301) on spontaneous emulsification induced by charged magnetite colloids and show that this type of self-assembly is quite generic with respect to the composition of the nanoparticles adsorbing at the oil-water interface. Moreover, we provide additional experimental evidence for the thermodynamic stability of these mesoemulsions, including spontaneous oil dispersal imaged by confocal microscopy and monitored in situ by time-resolved dynamic light scattering. We discuss the possibility that thermodynamic stability of the emulsions is provided by the negative tension of the three-phase line between oil, water, and adsorbed colloids.
Silica Particles as Surfactant Nanocarriers for Enhanced Oil Recovery
Springer series in materials science, 2021
The adsorption of mixed surfactants on solid substrates is important in a wide range of technological and industrial applications. Surfactant flooding in oil reservoirs is one of the most successful processes employed in enhanced oil recovery (EOR), where surfactant aqueous solutions are injected in the reservoir in order to decrease oil/water interfacial tension, leading to an increase in oil production. However, it suffers from a severe economic drawback due to the loss of large amounts of surfactant, which end up adsorbed on the rocks surface. This problem can be overcome with the use of systems of surfactant-modified silica particles that would be able to permeate through the rocks pores and either deliver the surfactants at the oil/water interface or act themselves as amphiphilic nanoagents, reducing the interfacial tension. For this purpose, we investigated the adsorption behavior of a nonylphenylethoxylate (NP10) on silica nanoparticles, mediated by the co-adsorption of a cationic surfactant (cetyltrimethylammonium bromide, CTAB). While NP10 alone shows meager adsorption, because of the lack of electrostatic interactions, CTAB adsorbs significantly on the oppositely charged silica surface. The adsorption isotherms of the binary surfactant mixtures at different molar ratios showed a sharp increase of NP10 adsorption on the silica/water interface in the presence of CTAB. Saturation values are reached at concentrations of NP10 higher than the critical micelle concentration, indicating significant adsorption on the nanoparticles. The adsorbed CTAB molecules would be probably acting as nucleating sites to form mixed aggregates with NP10 on the silica surface, through hydrophobic interactions with the CTAB hydrocarbon chain and would be responsible for the marked adsorption synergy between the two surfactants. The oil/water interfacial tension results suggest that the studied systems present a good potential as surfactant nanocarriers for EOR.
Energy & Fuels, 2018
Efficient phase separation of oil and water in emulsions is critical for water treatment processes and hydrocarbon processing. Our research aims at elucidating the separation of water-in-oil emulsions using silica nanoparticles (SNP's). By probing the surfactantnanoparticle interactions, we showed that surfactant stabilized emulsions can be destabilized depending on the nanoparticle wettability and the mode of nanoparticle addition. The efficiency of nanoparticles to demulsify surfactant stabilized emulsions depended on both the nanoparticle and surfactant concentration. Water-in-oil emulsions were destabilized when partially hydrophobic nanoparticles were added to the surfactantstabilized emulsion after emulsion formation (post-mixing). Hydrophilic and partially hydrophobic nanoparticles adsorb the surfactants via hydrogen bonding that in turn leads to depletion of surfactants at the oil-water interface. Upon the addition of hydrophilic nanoparticles, the preferential distribution of nanoparticles in the water phase led to lower adsorption of surfactants from the oil phase resulting in inefficient destabilization as compared to partially hydrophobic nanoparticles. Water-in-oil emulsions were not destabilized upon post-mixing hydrophobic nanoparticles due to weak hydrophobic interactions between surfactants and hydrophobic nanoparticles. For a fixed concentration of nanoparticles of specific wettability, changing the mode of nanoparticle addition
Journal of Colloid and Interface Science, 2019
There is a notable paucity of studies investigating the impact of charged nanoparticles on the interfacial behavior of nonionic surfactants, assuming that the interactions are negligible in the absence of electrostatic forces. Here, we argue about our observations and the existence of a complex interfacial behavior in such systems depending on the type and chemical structure of surfactant. This study set out to investigate the effects of interactions between hydrophilic silica nanoparticles (NP) and non-ionic surfactants on water/heptane dynamic interfacial properties using drop profile analysis tensiometry (PAT). Three surfactants were studied, namely Triton X-100 (significantly soluble in water phase), C 12 DMPO (well soluble in both phases) and SPAN 80 (oil-soluble). The different chemical structures and partition coefficients of the surfactants enabled us to cover possible interactions and differentiate between bulk and interfacial interactions. We observed that hydrophilic silica NPs had a negligible effect on the interfacial behavior of Triton X-100, that they increased the surface activity of C 12 DMPO when both compounds are initially in the aqueous phase. Most interestingly is that the added NPs generated unstable interfacial NP-surfactant complexes and reduced the pseudo-equilibrium interfacial tension of oil-soluble surfactant, Span 80, even though NPs and surfactants were in different bulk phases.
Molecular Dynamics Study of Nanoparticles and Non-Ionic Surfactant at an OilWater Interface
2020
Nanoparticles (NPs) and surfactants can spontaneously concentrate at the interface between two immiscible liquids, such as oil and water. Systems of high oil-water interfacial area, such as emulsions, are the basis of many industries and consumer products. Although NPs and surfactants are currently incorporated into many of these applications, their mutual interfacial behavior is not completely understood. Here we present molecular dynamics simulations of NPs and non-ionic surfactant in the vicinity of an oil-water interface. It was found that in low concentration the surfactants and NPs show cooperative behavior in lowering the oil-water interfacial tension, while at higher surfactant concentration this synergy is attenuated. It was also found that binding of surfactants to the NP surface decreases the surfactant efficiency in lowering the interfacial tension, while concurrently creating a barrier to NP aggregation.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999
Phospholipid-stabilised emulsions are known to have a poor stability when prepared in the presence of electrolytes. In order to try to circumvent this problem, submicron-sized 5% o/w emulsions were prepared in the presence of up to 500 mM KCl or up to 50 mM CaCl 2 using either only steric stabilisers or a combination of steric stabilisers and phospholipids. Steric surfactants are believed to provide a steric repulsion barrier around the emulsion droplets, and as such should withstand electrolyte addition better than the mainly electrostatically-stabilised phospholipid emulsions. The emulsion stability was investigated by measuring the particle size of the emulsion droplets as a function of time by photon correlation spectroscopy. Emulsions stabilised only by 0.5% (w/v) of the steric surfactants were completely stable in the presence of electrolytes. It was also shown that the addition of even low concentrations of the steric surfactants (0.025% to 0.05%) indeed dramatically improved the stability of phospholipid-stabilised emulsions in the presence of electrolytes.
Nanoparticle-Stabilized Emulsions for Applications in Enhanced Oil Recovery
Nanoparticle-stabilized emulsions have attracted many researchers' attention in recent years due to many of their specific characteristics and advantages over conventional emulsions stabilized by surfactants or by colloidal particles. For example, the solid nanoparticles can be irreversibly attached to the oil-water interface and form a rigid nanoparticle monolayer on the droplet surfaces, which induce highly stable emulsions. Those emulsions can withstand harsh conditions. Compared to colloidal particles, nanoparticles are one hundred times smaller, and emulsions stabilized by them can travel a long distance in reservoirs without much retention.
Journal of Petroleum Science and Engineering, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Oil-in-Water Emulsions Stabilized by Highly Charged Polyelectrolyte-Grafted Silica Nanoparticles †
Langmuir, 2005
Fully sulfonated poly(styrenesulfonate) brushes were grown from the surface of colloidal silica particles and used to prepare stable trichloroethylene-in-water and heptane-in-water Pickering emulsions. These particles were highly charged and colloidally stable in water but could not be dispersed in trichloroethylene or heptane. Both two-phase (emulsion plus neat water) and three-phase (emulsion separating neat oil and water phases) systems were observed, with water-continuous emulsion phases in all cases. Emulsion phases containing as much as 83% (v/v) oil were stable for over six months. Poly(styrenesulfonate)-grafted particles were very efficient emulsifiers; stable emulsion phases were prepared when using as little as 0.04 wt% particles. The emulsifying effectiveness of the poly(styrenesulfonate)-grafted silica particles can be attributed to the hydrophobicity of the vinylic polymer backbone that makes this highly charged polyelectrolyte unusually surface active at the oil/water interface. † Part of the Bob Rowell Festschrift special issue.