Abstract
The extraction of carbon into concentrates during flotation of graphite ores does not exceed 75–88 %, which is due to the inconsistent quality of the processed ores and the inconsistent composition of the main collecting agent – i.e. burning kerosene, which, apart from hydrocarbons, also contains oxygen containing compounds. The effect of its components in the flotation of graphite has not been studied, and the findings regarding the effect produced by individual organic compounds are scarce. This makes it a more challenging job to identify which reagents among oil refinery and petrochemical products would be more effective.
The authors looked at the effect produced by hydrocarbons representing the main classes, as well as by oxygen containing compounds. To analyse how hydrocarbons interact with the graphite surface, using the atom-atom approximation, a potential function of the intermolecular interaction was calculated as the sum of the potentials φ_ij in the intermolecular interaction between the i number of molecular force centres and the j number of solid state atoms. Buckingham-Corner equation was used for the potential calculations. The following bonds were taken as the molecular force centres: CH3 and CH2 for alkanes, C and H atoms for alkenes and aromatic hydrocarbons, and CH2 for cyclohexane. The obtained values of the potential function of the intermolecular interaction between hydrocarbons and the graphite surface are fairly close to the enthalpy values obtained through gas adsorption chromatography. The values of free energy (-ΔG) and entropy of adsorption (-ΔS) were also calculated. An LKhM-8MD-5 chromatograph equipped with a flame ionization detector was used in the study, with helium used as the carrier gas at a flow rate of 40 cm3/min. The thermodynamic characteristics of the adsorption of carboxylic acids, alcohols, ethers and esters, aldehydes and ketones were determined based on chromatography data. The adsorption heat was calculated based on an additive scheme and using heat increments for individual bonds. It is shown that the functional groups with locally concentrated electron density that are present in the molecules stimulate a specific (however, still molecular) interaction between the compounds and the graphite surface, which enhances the thermodynamic characteristics of adsorption. As the adsorption capacity intensifies, the groups create the following row: =CO, -O-, -COO-, -COH, -OH, -COOH. The most important parameters defining adsorption include the number of carbon atoms in the radicals, their composition and structure, valence state, the presence and the properties of functional groups. The results of a graphite flotation test, which was performed on a non-frothing unit, indicate that the flotation activity of all compounds increases with the increase in the number of carbon atoms in the molecules. Alkanes, alkenes and aromatic hydrocarbons proved to have the highest flotation activity. There is no correlation between the adsorption capacity and the flotation activity of various compounds. A classification of the studied hydrocarbons and oxygen containing compounds was developed based on their flotation activity. On the basis of the above mentioned classification, the authors proposed three reagents, which are protected with certificates of authorship. The results of the froth flotation test conducted for graphite ore showed that the reagents that mainly contain high molecular weight paraffins and aromatic hydrocarbons offered the most effective graphite collecting agents.
Keywords
Graphite, hydrocarbons, оxygen containing compounds, thermodynamic characteristics of adsorption, flotation, non-specific and specific interaction, intermolecular interaction, functional groups.
1. Vasumathi N. Vijaya Kumar T.V., Ratchambigai S., Subba Rao S., Bhaskar Raju G. Flotation studies on low grade graphite ore from eastern India. International Journal of Mining Science and Technology. Vol. 25, iss. 3, 2015, pp. 415–420.
2. Kaya Ö.М., Canbazoğlu М. A study on the floatability of graphite ore from yozgat akdağmadeni (turkey). The Journal of ORE DRESSING. 2007, vol. 9, iss. 17.
3. Khanchuk A.I., Didenko A.N., Rasskazov I.Yu., Berdnikov N.V., Aleksandrova T.N. Graphite schists as a prospective source of precious metals in Russia’s Far East. Vestnik DVO RAS [Vestnik of the Far East Branch of the Russian Academy of Sciences], 2010, no. 3, рр. 3–12. (In Russ.)
4. Hongqiang, L.I., Leming O.U., Qiming FENG, Ziyong CHANG. Recovery mechanisms of sericite in microcrystalline graphite flotation. Physicochem. Probl. Miner. Process. 51(2), 2015, pp. 387−400.
5. Yangshuai Qiu, Yongfu Yu, Lingyan Zhang, Yupeng Qian, Zhijun Ouyang. An Investigation of Reverse Flotation Separation of Sericite from Graphite by Using a Surfactant: MF. Minerals. 2016. 6, 57; doi:10.3390/min6030057.
6. Bragina V.I., Baksheeva I.I. Development of a beneficiation process for graphite ores. Gonyi informatsionno-analitichesky byulleten [Mining Information and Analytical Bulletin], 2012, no. 9, рр. 133–137. (In Russ.)
7. Dmitriev A. Chemical Purification of Flakelike Cryptocristalline Graphite Powder. Basharin I., Bocharnikov V. Annual World Conference on Carbon 2011, Shamghai, China. Vol.1, pp. 180–182.
8. Dmitriev A.V., Bocharnikov V.A., Velikodneva E.D., Basharin I.A. Chemical refining of flaked crypto-cristalline graphite. Vestnik Yugorskogo gosudarstvennogo universiteta [Bulletin of the Yugra State University], 2014, no. 2 (33), pp. 24–26. (In Russ.)
9. Kiselev A.V., Poshkus D.P., Yashin Ya.I. Molekulyarnye osnovy adsorbtsionnoy khromatografii [Molecular basis of adsorption chromatography]. Moscow: Khimiya, 1986, 272 р. (In Russ.)
10. Kiselev A.V. Mezhmolekulyarnye vzaimodeystviya v adsorbtsii i khromatografii [Intermolecular interactions in adsorption and chromatography]. Moscow: Vysshaya shkola, 1987, 335 р. (In Russ.)
11. Avgul N.N., Kiselev A.V., Poshkus D.P. Adsorbtsiya gazov i parov na odnorodnykh poverkhnostyakh [Adsorption of gases and vapors on homogeneous surfaces]. Moscow: Khimiya, 1975, 384 p. (In Russ.)
12. Chizhevsky V.B. Fiziko-khimicheskie osnovy i intensifikatsiya protsessa flotatsii graphitovykh rud: dis. … d-ra tekhn. nauk [Physical and chemical basis and process intensification in graphite ore flotation: Doctoral dissertation]. Magnitogorsk, 1990, 416 p. (In Russ.)
13. Vyakhirev D.A., Shushunova A.F. Rukovodstvo k prakticheskim rabotam po gazovoy khromatografii [A guide to practical work on gas chromatography]. Leningrad: Khimiya, 1988, 338 p. (In Russ.)
14. Kiselev A.V., Yashin Ya.I. Adsorbtsionnaya gazovaya i zhidkostnaya khromatografiya [Gas and liquid adsorption chromatography]. Moscow: Khimiya, 1979, 228 р. (In Russ.)
15. Nesmeyanov A.N., Nesmeyanov N.A. Nachala organicheskoy khimii [Principles of organic chemistry]. Moscow: Khimiya, 1974, vol. 1, 624 р. (In Russ.)
16. Kiselev A.V., Yashin Ya.I. Gazoadsorbtsionnaya khromatografiya [Gas adsorption chromatography]. Moscow: Nauka, 1967, 256 р. (In Russ.)
17. Glembotsky V.A. On the theoretical basis of apolar reagents and their action. Obogashchenie rud [Beneficiation of ores], 1980, рр.13–27. (In Russ.)
18. Grabowski, B. Graphite flotation in the presence of sodium acetate. B. Grabowski and J. Drzymała. Annales universitatis Mariae Curie - Skłodowska Lublin – Polonia Wrocław Technical University, Wybrzee Wyspianskiego 27, 50-370 Wrocław, Poland VOL. LXIII, 6 SECTIO AA 2008, pp. 68−72.
19. Ravichandran V. Eswaraiah C., Manisankar P. Beneficiation of low grade graphite ore deposits of Tamilnadu (India). Ultra Chemistry. 2012. Vol. 8(2), pp. 159–168.
20. Ryaboy V.I., Shepeta E.D., Kretov V.P., Levkovets S.E., Ryaboy I.V. Influence of the surface-active properties of the reagents containing sodium dialkyl-dithiophosphates on the flotation of sulfides. Balkan Mineral Processing Congress 16th; 2015. Belgrade. June 17-19, 2015. Vol. 1, pp. 321–326.
21. Chizhevsky V.B. Flotation properties of alcohols. Obogashchenie rud [Beneficiation of ores], 1988, no. 3, рр. 16–19. (In Russ.)
22. Glembotsky V.A. Osnovy fiziko-khimii flotatsionnykh protsessov. 2-e izd., pererab. i dop. [Fundamental physics and chemistry behind flotation processes. 2nd revised edition]. Moscow: Nedra, 1980, 471 р. (In Russ.)