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Adsorption of quaternary ammonium salt hydrophobic modifiers on the α-quartz (001) surface : a density functional theory study

100%

Liu C. , Wang W. , Wang H. , Zhu C. , Ren B.

tom Vol. 59, iss. 3

art. no. 170260

To investigate the adsorption mechanism of quaternary ammonium salt on the α-quartz (001) surface, the adsorption models of hydrophobic modifiers 1231, 1431, 1631 and 1831 were constructed and simulated using the density functional theory (DFT). Results indicate that the adsorption energy of quaternary ammonium salt increases with the increase of carbon chain length, and the adsorption energy reaches the maximum at 18 carbon atoms; however, the adsorption capacity of 1631 is weak owing to the carbon chain deflection. Based on the Mulliken bond population analysis, reagent 1831 has the strongest interaction with α-quartz (001) surface compared with 1231, 1431 and 1631; and during the adsorption process, charge transfer and electrostatic attraction occur between the reagent and α-quartz (001) surface with similar degrees of charge transfer observed. This study emphasizes that electrostatic attraction plays a key role in the adsorption process, while the week hydrogen bonding plays a secondary role.

Reverse anionic flotation of dolomitic collophanite using a mixed fatty acid collector : adsorption behavior and mechanism

88%

Xu W. , Liang Q. , Tian Y. , Mei G.

Physicochemical Problems of Mineral Processing

2022

tom Vol. 58, iss. 4

art. no. 151519

Collophanite in south China generally has a high MgO level, which negatively impacts wet-process phosphoric acid production and cannot be utilized directly. A novel mixed fatty acid soap (GSWF01) was employed as a collector for dolomite. A single reverse flotation experiment was performed on a dolomitic collophanite from Guizhou, China under different pH and collector dosages. A phosphate concentrate with P2O5 grade of 33.73%, MgO content of 1.07%, MER value (ω(MgO+Al2O3+Fe2O3)/ω(P2O5)) of 4.86% and phosphorus recovery of 91.06% was obtained. The beneficiation indexes of GSWF01 were better than that of sodium oleate (NaOL). The adsorption behavior and mechanism of GSWF01 on dolomite surface were investigated using quartz crystal microbalance with dissipation (QCM-D), atomic force microscope (AFM), infrared spectrometer (IR), and zeta potentiometer. The results revealed that GSWF01 chemically reacted with metal ions (Ca2+, Mg2+, etc.) on the surface of dolomite to generate fatty acid salt precipitation (chemisorption). The adsorbed layer transitioned from dense to loose in two stages, resulting in a stable double-layer adsorption structure. Moreover, in a weak acidic solution environment, physical adsorption of fatty acid molecules (RCOOH ((aq)) and fatty acid ion-molecular association compounds (RCOOH• RCOO-) generated by hydrolysis can also occur on the dolomite surface. These are the main reasons for the hydrophobic floating of dolomite. This is of great significance to the development of a novel high-efficiency dolomite collector and the enhancement of flotation process for carbonate collophanite.

Mechanism of adsorption in cylindrical nanopores. The roles of adsorbate-adsorbate interactions in stabilizing the adsorbed phase

75%

Kuchta B. , Firlej L.

Materials Science Poland

2006

tom Vol. 24, No. 2/2

432--442

Mechanism of adsorption in nanometric cylindrical pores has been analysed. Grand canonical Monte Carlo simulations were performed for two model systems: krypton and argon, adsorbed in an ideal (smooth) cylindrical silica pore of diameter 2R = 4 nm. The role of interatomic (adsorbate-adsorbate) interactions and atom-wall (adsorbate-adsorbent) forces in the mechanism of adsorption has been discussed. It has been shown that the correlation between these two energy components plays a crucial role in layering and capillary condensation transitions. The stability of different stages of adsorption has been analysed and discussed taking into consideration fluctuations of energy and number of adsorbed atoms during simulations.

Thiabendazole fungicide adsorption onto four agricultural soils collected from the Loukkos area of northwestern Morocco

63%

El Azzouzi L. , El Aggadi S. , Ennouhi M. , Ennouari A. , El Fadil I. , Zrineh A.

Ecological Chemistry and Engineering. S

2022

tom Vol. 29, nr 2

217--226

A serious environmental problem can arise from the presence of pesticides in soils and waters. Hence, in this study we have carried out the adsorption of the Thiabendazole fungicide onto four soils collected from several areas in Morocco as Larache, Laouamra, Ksar kebir and Tlata drissana. Physicochemical properties, elemental analysis, X-ray diffraction (XRD) were investigated to characterise the four selected soils. The experimental equilibrium data were analysed using Langmuir, Freundlich models. The equilibrium data were best described by a Langmuir model for all adsorbents. The maximum estimated adsorption capacity was 0.747 mg∙g–1, 0.751 mg∙g–1, 0.473 mg∙g–1 and 1.083 mg∙g–1, for Larache, Laouamra, Ksar kebir and Tlata drissana soils, respectively.