Preferential Adsorption of Long-chain Normal Paraffins on MoS2, WS2 and Graphite from n-Heptane

Groszek, A. J.

doi:10.1038/204680a0

Cited by 73 publications

(60 citation statements)

References 1 publication

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“…This hypothesis is supported by the fact that perpendicular lamellae were always observed on HOPG, [7±9] and only tilted lamellae were detected on the basal plane of MoS 2 plane, [10,11,27] while the heat of adsorption for n-dotriacontane (nC 32 H 66 ) on MoS 2 was measured to be approximately 1 = 3 of the value obtained on graphite. [28] We deduce that the alkane±gold interaction is in between the alkane--HOPG, and the alkane±MoS 2 interactions is such that both perpendicular and tilted lamellae are observed for 38 > n ! 22 at room temperature.…”

Section: Resultsmentioning

confidence: 96%

Self‐Assembly of Normal Alkanes on the Au (111) Surfaces

Zhang

Xie

Mao

et al. 2004

Chemistry A European J

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The self-assembled monolayers (SAMs) of normal alkanes (n-C(n)H(2n+2)) with different carbon chain lengths (n=14-38) in the interfaces between alkane solutions (or liquids), and the reconstructed Au (111) surfaces have been systematically studied by means of scanning tunneling microscopy (STM). In contrast to previous studies, which concluded that some n-alkanes (n=18-26) can not form well-ordered structures on Au (111) surfaces, we observed SAM formations for all these n-alkanes without any exceptions. We find that gold reconstruction plays a critical role in the SAM formation. The alkane monolayers adopt a lamellar structure in which the alkane molecules are packed side-by-side, to form commensurate structures with respect to the reconstructed Au (111) surfaces. The carbon skeletons are found to lie flat on the surfaces, which is consistent with the infrared spectroscopic studies. Interestingly, we find that two-dimensional chiral lamellar structures form for alkanes with an even carbon number due to the specific packing of alkane molecules in a tilted lamella. Furthermore, we find that the orientation of alkane molecules deviates from the exact [011] direction, because of the intermolecular interactions among the terminal methyl groups of neighboring lamellae; this results in differences of molecular orientation between mirror structures of adjacent zigzag alkane lamellae. Structural models have been proposed, that shed new light on monolayer formation.

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Section: Resultsmentioning

confidence: 96%

Self‐Assembly of Normal Alkanes on the Au (111) Surfaces

Zhang

Xie

Mao

et al. 2004

Chemistry A European J

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“…Nonpolar hydrocarbon oils (saturated hydrocarbons) such as kerosene, diesel oil, transformer oil and solar oil are normally used as molybdenite flotation collectors [6][7][8][9]. However, they only adsorb on the nonpolar face of molybdenite by hydrophobic interactions and van der Waals forces [10][11][12][13][14][15], because the surface energy of nonpolar hydrocarbon oils is similar to that of molybdenite faces. Therefore, the hydrophobicity of molybdenite edges cannot be improved by nonpolar hydrocarbon oils [16,17].…”

Section: Introductionmentioning

confidence: 99%

The Influence of Ca2+ and pH on the Interaction between PAHs and Molybdenite Edges

Wan

Yang

et al. 2017

Minerals

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Nonpolar hydrocarbon oils are widely used as collectors for floating molybdenite. However, they can only adsorb on molybdenite faces and not on molybdenite edges, resulting in limited molybdenite recovery, especially in processed water containing a high amounts of Ca 2+ . In this study, the influence of Ca 2+ and pH on the adsorption of polycyclic aromatic hydrocarbons (PAHs), as part of composite collection on molybdenite edges, was studied. It was found that PAHs could only adsorb on molybdenite edges in the presence of Ca 2+ . Ca 2+ reacted with molybdenite edges to form CaMoO 4 precipitates. Then, CaMoO 4 precipitates interacted with PAHs to form a structure of π-cation-π by (1) the cation-π interaction, (2) the π-π interaction and (3) the electrostatic interaction. It was also found that CaMoO 4 precipitates on molybdenite edges promoted the adsorption of PAHs. The more the CaMoO 4 precipitates, the easier the PAHs adsorption occurred. As a result, the high amount of Ca 2+ and low pH enhanced the adsorption of PAHs on molybdenite edges. This study provides insights into reducing the deleterious effect of Ca 2+ on fine molybdenite flotation.

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“…Finally, calorimetric measurements have indicated that dotriacontane (n-C 32 ) adsorbs onto MoS 2 and WS 2 surfaces from heptane solution, although with substantially smaller heats of adsorption than on corresponding graphite surfaces. [7] A number of molecular simulation investigations have also demonstrated that paraffin molecules adsorb parallel to solid interfaces. Numerical computations simulating n-C 28 on hematite (a-Fe 2 O 3 ) surfaces suggest that the n-C 28 carbon plane lies flat in relation to the anionically terminated (1012) plane while the carbon plane is tilted in relation to cationically terminated (0001) plane.…”

Section: Introductionmentioning

confidence: 98%

A Quartz Crystal Microbalance Characterization of Metal‐Oil Interfaces and Interactions with Wax Molecules

Paso

Kompalla

Aske

et al. 2008

Journal of Dispersion Science and Technology

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The solid-liquid interface between stainless steel and model petroleum fluids is investigated at isothermal conditions using a quartz crystal microbalance. AISI 316 (Fe/Cr18/Ni10/Mo3) stainless steel is chosen to represent the metal surface. Paraffin components dissolved in dodecane constitute the petroleum fluid phase. Commercial macro-crystalline and microcrystalline waxes provide primarily linear and branched paraffin components, respectively. Paraffin solubility conditions are established through a van't Hoff relationship. Model fluids prepared with the single-component alkanes n-C 36 or n-C 30 paraffin provide well-defined solubility conditions. Monitored changes in resonance frequency and energy dissipation of the quartz crystal resonator immersed in the model fluids confirm that no continual deposition of paraffin components occurs at isothermal conditions. Solid paraffin crystals dispersed in solution show no adherence to the stainless steel surface. The absence of attractive interactions between the stainless steel surface and the dispersed paraffin crystals suggests that a surface adsorption and/or surface nucleation mechanism is responsible for the formation of incipient paraffin wax deposits under nonquiescent conditions.

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Preferential Adsorption of Long-chain Normal Paraffins on MoS2, WS2 and Graphite from n-Heptane

Cited by 73 publications

References 1 publication

Self‐Assembly of Normal Alkanes on the Au (111) Surfaces

Self‐Assembly of Normal Alkanes on the Au (111) Surfaces

The Influence of Ca2+ and pH on the Interaction between PAHs and Molybdenite Edges

A Quartz Crystal Microbalance Characterization of Metal‐Oil Interfaces and Interactions with Wax Molecules

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