Dynamic contact angles on PTFE surface by aqueous surfactant solution in the absence and presence of electrolytes

Chaudhuri, Rajib Ghosh; Paria, Santanu

doi:10.1016/j.jcis.2009.05.033

Cited by 93 publications

(65 citation statements)

References 40 publications

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“…The ability of specific ions to stabilize or disrupt organic-water interfaces by modifying surface hydration or direct ion-pairing interactions is described by the Hofmeister series (42)(43)(44). Broadly, an organic-water interface is stabilized by weakly positive or strongly negative ions, and destabilized by strongly positive or weakly negative ions.…”

Section: Resultsmentioning

confidence: 99%

Nanometer-Scale Chemistry of a Calcite Biomineralization Template: Implications for Skeletal Composition and Nucleation

Branson

Bonnin

Perea

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Plankton, corals, and other organisms produce calcium carbonate skeletons that are integral to their survival, form a key component of the global carbon cycle, and record an archive of past oceanographic conditions in their geochemistry. A key aspect of the formation of these biominerals is the interaction between organic templating structures and mineral precipitation processes. Laboratory-based studies have shown that these atomic-scale processes can profoundly influence the architecture and composition of minerals, but their importance in calcifying organisms is poorly understood because it is difficult to measure the chemistry of in vivo biomineral interfaces at spatially relevant scales. Understanding the role of templates in biomineral nucleation, and their importance in skeletal geochemistry requires an integrated, multiscale approach, which can place atom-scale observations of organic-mineral interfaces within a broader structural and geochemical context. Here we map the chemistry of an embedded organic template structure within a carbonate skeleton of the foraminifera Orbulina universa using both atom probe tomography (APT), a 3D chemical imaging technique with Ångström-level spatial resolution, and time-of-flight secondary ionization mass spectrometry (ToF-SIMS), a 2D chemical imaging technique with submicron resolution. We quantitatively link these observations, revealing that the organic template in O. universa is uniquely enriched in both Na and Mg, and contributes to intraskeletal chemical heterogeneity. Our APT analyses reveal the cation composition of the organic surface, offering evidence to suggest that cations other than Ca 2+ , previously considered passive spectator ions in biomineral templating, may be important in defining the energetics of carbonate nucleation on organic templates. biomineralization | templating | foraminifera | geochemistry | paleoceanography

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Section: Resultsmentioning

confidence: 99%

Nanometer-Scale Chemistry of a Calcite Biomineralization Template: Implications for Skeletal Composition and Nucleation

Branson

Bonnin

Perea

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…When a drop of electrolyte solution is placed on a soil surface, the cations in the solution would be adsorbed on the soil surface. From a thermodynamic viewpoint, adsorption of ions at the interface will decrease the solid-liquid interfacial free energy (Chaudhuri and Paria 2009), which will result in decreasing contact angle (Eq. 2).…”

Section: Resultsmentioning

confidence: 99%

“…This might be explained using the adsorption of univalent and divalent cations at the solid-liquid interfaces. Adsorption of ions at the solid-liquid interface will decrease the interfacial energy (Chaudhuri and Paria 2009), which will result in decreasing contact angle as explained in Eq. 2.…”

Section: Resultsmentioning

confidence: 99%

Soil-water contact angle as affected by the aqueous electrolyte concentration

Leelamanie

Karube

2013

Soil Science and Plant Nutrition

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Electrolyte concentration changes the surface tension of the water-air interface, which is expected to affect the solid-water contact angle. In the present study, we focused on examining the effects of aqueous electrolyte concentration on the contact angle of soil samples with different hydrophobicities using sodium chloride (NaCl) and calcium chloride (CaCl 2 ) solutions. Japanese Andisol and silica sand were hydrophobized using stearic acid to obtain different hydrophobicities. The contact angle of all the samples increased with increasing electrolyte concentration. This was attributed to the increasing surface tension of the solutions. The response of contact angle to the electrolyte concentration was positively correlated with soil surface free energy fitting into a linear relationship in Andisol, but not in silica sand. Surface tension of electrolyte solutions increases linearly with electrolyte concentration up to high salinities, and the contact angle can be expected to increase with increasing electrolyte concentration in a corresponding pattern. The relationship observed in the present study was non-linear, where more prominent increase of contact angle was observed at low electrolyte concentrations. The response of contact angle to the increasing electrolyte concentration was almost negligible at concentrations higher than 0.06 mol L ) for CaCl 2 solutions. The lowered solid-liquid interfacial free energy and its effects on contact angle with increasing adsorption of ions at the interface was considered to be the reason for decreasing slopes of the curves. Initial increase in contact angle with increasing ionic strength of CaCl 2 was lower than that of NaCl. This might be because the adsorption of ions on soil surfaces, and the consequent effects on lowering the free energy of the solid-liquid interface and the contact angle, are more pronounced for calcium ions (Ca 2+ ) than for sodium ions (Na + ).

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“…air/water interface) resulting from the restoration of hydrophobicity of the membrane as the foulant is removed during water permeation, and the subsequent decrease in contact angle at the PTFE surface as the foulant is dissolved and decreases the surface tension of the water. A decrease in surface tension of the solution has been found to decrease the contact angle on the PTFE surface [30]. …”

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confidence: 97%

Fouling mechanisms of dairy streams during membrane distillation

Hausmann

Sartipy

Vasiljevic

et al. 2013

Journal of Membrane Science

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This study reports on fouling mechanisms of skim milk and whey during membrane distillation (MD) using polytetrafluoroethylene (PTFE) membranes. Structural and elemental changes along the fouling layer from the anchor point at the membrane to the top surface of the fouling layer have been investigated using synchrotron IR micro-spectroscopy and electron microscopy with associated energy dispersive X-ray spectroscopy (EDS). Initial adhesion of single components on a membrane representing a PTFE surface was observed in-situ utilizing reflectometry. Whey components were found to penetrate into the membrane matrix while skim milk fouling remained on top of the membrane. Whey proteins had weaker attractive interaction with the membrane and adhesion depended more on the presence of phosphorus near the membrane surface and throughout to establish the fouling layer. This work has given detailed insight into the fouling mechanisms of MD membranes in major dairy streams, essential for maintaining membrane distillation operational for acceptable times, therewith allowing further development of this emerging technology. 2 IntroductionMembrane distillation (MD) is a thermally driven membrane process and relies on a highly hydrophobic porous membrane to maintain a liquid-vapour interface. Common membrane materials for MD are polypropylene (PP), polyvinylidene fluoride (PVDF) and PTFE [1,2]. The highest performing membrane material for MD is PTFE due to its high hydrophobicity, chemical inertness and open porous structure [3]. Fouling in the MD process is different to that observed in pressure driven processes such as RO. The low operating pressure used in MD may potentially lead to a less compact, more easily removed, fouling layer. Also, since only volatile compounds pass through the membrane pores, the potential for in-pore fouling is minimized in MD applications. Studies of MD processes have, however, revealed that penetration of foulants into the membrane can occur in some instances [4]. There is a need for a better understanding how dairy components interact with MD membranes and accumulate at the membrane surface. This understanding may allow better control of performance of membrane distillation via better mitigation of fouling.The high hydrophobicity of MD membranes can result in the establishment of hydrophobic interactions between the membrane and any solutes that have hydrophobic components, such as proteins and fats. While hydrophilic coatings may be a possible avenue to reduce the fouling that results from these hydrophobic interactions [5][6][7], simple uncoated membranes have advantages in terms of lower cost and can be easier to manage over time as there is no requirement to maintain a specialised surface coating.There are numerous studies on fouling phenomena occurring with dairy components [8][9][10][11][12][13], however little can be found on the actual mechanisms behind the fouling. Most studies focus on membrane performance, not investigating kinetics behind fouling phenomena observed. In cases wh...

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Dynamic contact angles on PTFE surface by aqueous surfactant solution in the absence and presence of electrolytes

Cited by 93 publications

References 40 publications

Nanometer-Scale Chemistry of a Calcite Biomineralization Template: Implications for Skeletal Composition and Nucleation

Nanometer-Scale Chemistry of a Calcite Biomineralization Template: Implications for Skeletal Composition and Nucleation

Soil-water contact angle as affected by the aqueous electrolyte concentration

Fouling mechanisms of dairy streams during membrane distillation

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