Adsorption Properties of the Natural Carbon–Mineral Sorbent Shungite

Abstract

Physicochemical methods were used for a comprehensive study of the structural/sorption properties of the natural mineral shungite. It was shown that the composite structure of the mineral determines its main physicochemical characteristics. The isosteric heat of adsorption of water vapour was estimated by calorimetric methods as 70 kJ/mol. This value corresponds to the interaction of water molecules with the vicinal hydroxy groups of the silica constituent of shungite; adsorption heats with values in the range 40-45 kJ/mol are characteristic of the carbon constituent of the sorbent. The heat of adsorption of benzene onto shungite was higher than that for hexane adsorption onto the mineral, indicating that specific interaction occurs between the benzene molecules and the active centres which exist on both the carbon and silica constituents of the mineral. It was shown that the adsorption parameters of shungite with respect to organic compounds which dissociate in an anionic manner suggest that the mineral could be applied as a filtering material with a sorptive action for water cleansing.

Adsorption hysteresis at low relative pressures

“…A number of systems were examined to check the proposed method for calculating the H3 hysteresis loop in the low pressure region: the adsorption of water at T = 298 K on a lunar soil sample [2], adsorption of water at T = 293 K on shungite [4] and kaolinite [3,7], and the adsorption of pyridine at T = 323 K on montmorillonite [5,6]. The corresponding adsorption-desorption isotherms are shown in Fig.…”

“…According to the commonly accepted theory of adsorption hysteresis, the abscissa of the extreme left-hand point of the hysteresis loop corresponds to relative pressure of the adsorbate in the bulk phase not less than p/p s » 0.4-0.5 [1]. On the other hand, considerable experimental work has shown that the H3 hysteresis loop continues into the low pressure region and often does not close even as p/p s ® 0 [2][3][4][5][6][7][8]. In 1957, Arnell and McDermot [9] proposed that hysteresis at low pressures should be attributed to the formation of traps in the adsorbent upon adsorption.…”

Adsorption Hysteresis in Open Slit-like Micropores

“…Adsorbents such as lunar regolith, shungite, and kaolinite are characterised by a high degree of adsorption deformation (swelling) compared to Al 2 O 3 . Additionally, these adsorbents form stronger covalent bonds with water molecules [ 19 , 20 , 21 , 22 , 23 , 24 ]. In this case, diffusional and chemical “traps” have higher values in comparison with the values of traps during the adsorption–desorption of water vapor on the Al 2 O 3 sample.…”

Shungite/poly(vinyl alcohol) hybrid hydrogels: An efficient adsorption material for rare earth metals in aqueous media

“…Shungite is also known as the most promising nanosorbent manufactured from ore which include carbon nanostructures and turbostratic carbon with different types of minerals such as quartz, pyrite, chlorite, and sericite. 17,18 The types of the shungite carbon are comprised of amorphous carbon, ordered graphite, fullerene, graphene layers, and glassy carbon. 19 Literature survey shows that shungite has excellent adsorption properties toward various organic compounds such as oleic acid, water-soluble resins, and amyl alcohol, and heavy metals such as Zn, Cd, Pb, Mn, Cr, Cu, and Ni in aqueous solution.…”