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Influence of grinding methods on the preparation of ultra-clean coal from slime

100%

Wang R. , Gao L. , Liu W. , Zhuo Q.

tom Vol. 58, iss. 6

art. no. 151957

This study discusses the technology of coal slime recovery for preparing ultra-clean coal (UCC). X-ray diffraction analysis (XRD) and scanning electron microscopy combined with energy dispersive spectroscopy (SEM-EDS) were used to analyze the characteristics of coal slime and to explore the types of minerals and embedded characteristics of coal slime. The particle interaction energy and contact angle analysis were used to determine the UCC preparation process through dry and wet grinding dissociation comparison and shear flocculation flotation tests, combined with zeta potential measurements. The results showed that the inorganic minerals in the slime were mainly kaolinite clay minerals, which were easy to mud in the pulp and needed grinding. The calculation results of the interaction energy indicated that the interaction force of dry-ground slime in the pulp was small, and flocculation was more likely to occur. The wet-ground product was subjected to three flotations to obtain UCC with an ash content of 0.95%.

Effect of Na+, Ca2+ on the hydration properties of quartz surface: a molecular dynamics simulation study

88%

Liu C. , Min F.-f. , Chen J. , Liu L.-y. , Ren B. , Lv K.

tom Vol. 58, iss. 3

art. no. 147452

Effects of metal ions on the surface hydration of fine quartz are investigated by the theoretical methodologies. The hydration layer on the quartz surface is made up of three layers of water molecules, about 8-10 Å. The interaction energy of ions changes from -1.071 eV in water to -1.821 eV (Na+) and -1.896 eV (Ca2+) when ions are present. Metal ions improve the interaction of water molecules with the quartz surface, allowing more water molecules to enter the second and third hydration layers. In the presence of Na+, the diffusivity of water molecules is greater than in Ca2+ solutions. Increased interaction between water molecules and surfaces in the order Ca2+ > Na+ is consistent with metal ions’ propensity to hydrate.

Isoelectronic dimers [(XH3)2, (YH2)2, (ZH)2, and (Rg)2] in the groups of the periodic system: ab initio quantum chemical calculations

75%

Hobza P. , Burda J. V. , Zahradnik R.

tom Vol. 72, nr 7S

1497-1504

The (ZH)2, (YH2)2, (XH3)2 and (Rg)2 dimers [Z=F-At; Y=O.Po; X=N, Bi; Rg=rare gas] were studied ab initio using the CCSD(T) and MP2 procedures. Average relativistic effective potentials were used for all the halogens, while Stuttgart effective core potentials were used for the remaining non-hydrogen atoms. All the (HX)2 structure are H-bonded. All the stabilization energies mutually approach when passing down the group of the periodic system.

Zinc ion adsorption on carbon nanotubes in an aqueous solution

75%

Ansari A. , Mehrabian M. A. , Hashemipour H.

tom Vol. 14, nr 3

29-37

The literature devoted to numerical investigation of adsorption of heavy metal ions on carbon nanotubes is scarce. In this paper molecular dynamics is used to simulate the adsorption process and to investigate the effect of the infl uencing parameters on the rate of adsorption. The predictions of the molecular dynamics simulation show that the adsorption process is improved with increasing the temperature, pH of solution, the mass of nanotubes, and surface modifi cation of CNT using hydroxyl and carboxyl functional groups. The results predicted by the model are compared with the experimental results available in the literature; the close agreement validates the accuracy of the predictions. This study reveals that the water layers around the carbon nanotubes and the interaction energies play important roles in the adsorption process. The study also shows that electrostatic force controls the attraction of zinc ions on the nanotube sidewall.

Efekt kooperatywności oddziaływań niekowalencyjnych w wybranych układach molekularnych stabilizowanych wiązaniami wodorowymi i halogenowymi

63%

Domagała M. , Dominikowska J. , Palusiak M.

2019

tom [Z] 73, 1-2

33--52

Among various so-called weak interactions, a halogen bond [8 and references therein] is currently probably one of more explored by researchers. This is due to the fact that it has several properties in common with the hydrogen bonding, and thus, similarly as already well characterised H-bond, it may have a crucial role in different physical, chemical, and biological processes. This bond is formed due to stabilising interactions between a region of positive charge located on a surface of the halogen atom and the other atomic center possessing the electron charge surplus (e.g. a lone pair) [8]. The region of positive charge appears on the halogen atom surface due to deformation of its electron cloud resulting in its ellipsoidal shape with the short axis opposite the covalent bond and the long axis in the perpendicular direction [11]. This results in a particular distribution of local charges on the atomic surface, as shown in Figure 1. As a consequence the halogen atom may exhibit a dual character, acting as either electron charge donor or acceptor, depending on the type of interaction and the direction of the appearing interactomic contact. A good example of such situation is shown in Figure 2. Thus, one may consider the situation when two interactions are formed simultaneously and the halogen atom acts as an electron charge donor and acceptor at the same time. For such situation the synergism of both interactions may strengthen complexation. In order to analyze that case, various representative complexes were investigated [13, 17, 18, 20, 21] by means of many-body interaction approach [5, 6]. In general, it appears that as distinct to hydrogen bond [2–4], the synergism is rather weak, with some exceptions for iodine atom due to stronger halogen bonds formed by that atomic centre [13, 17, 18]. In the case of halo-amine tetramers [21] the additional stabilising effect derived from back bonding of π type was found – for the first time for a halogen bond.