Quantum-chemical substantiation of the properties of the bioreagent oxidizing non-ferrous metal sulfides

The paper determines the structural formula and quantum chemical characteristics of the most energetically probable, stable conformation of the bioreagent molecule formed during the oxidation of iron (II) ions by the autotrophic mesophilic iron-oxidizing bacteria Acidithiobacillus ferrooxidans in a solution of sulfuric acid consisting of iron (III) ion and three acid residues of glucuronic acid.
The bioreagent oxidant is widely used in the industry for leaching metals from non-ferrous sulfide ores and enrichment concentrates.
The quantum chemical characteristics of the bioreagent molecule are analyzed in comparison with the characteristics of anhydrous iron (III) sulphate, also used in hydrometallurgy as an oxidizer. The structure and quantum-chemical characteristics are studied using the method of molecular computer simulation, the theory of boundary molecular orbitals, and the Pearson principle. It has been established that the most energetically probable, stable conformation of the bioreagent molecule contains the acid residues of glucuronic acid of a non-cyclic structure. According to the research results, the bioreagent refers to the more rigid Lewis acid – electron acceptor – than iron (III) sulphate. The bioreagent molecule is less polarized, characterized by lower absolute electronegativity and 2 times larger volume. A theoretical substantiation of the greater persistence of primary sulphides – pyrite, pentlandite, chalcopyrite, relative to the secondary minerals – pyrrhotine, chalcocite and covellite is proposed based on the calculated values of the boundary molecular orbitals, absolute stiffness and electronegativity of iron, copper and nickel sulfides. The bioreagent characteristics that determine the interaction efficiency – volume, heat of formation, steric energy and its components, total energy, etc. are many times greater than for Fe2(SO4)3. The high oxidative activity of the bioreagent relative to Fe2(SO4)3 can be justified by the higher partial charge of the iron atom, the greater length of bonds between atoms, the lower energy of the lower free molecular orbitals and the greater degree of charge transfer during the interaction of the bioreagent with the sulfide minerals.

1. Dew D.W., Miller D.M., Van Aswegan P.C. Genmin’s commercialization of the bacterial oxidation process for the treatment of refractory gold concentrates. In: Proc. Int. Gold Conf. (Beaver Creek, Randol, Golden, Colorado). 1993. P. 229—237.

2. Adamov EV, Panin V.V. Biotechnologia metallov: Kurs lecziy [Biotechnology of metals: Lecture course]. Mosсow: Utseba, MISiS, 2003.

3. Van Aswegen P.C., Van Niekerk J., Olivier W. The BIOXTM process for the treatment of refractory gold concentrates. In: Biomining (Eds. Rawlings D.E., Johnson B.D.). Berlin: Springer, 2007. P. 1—34.

4. Kaksonen A.H., Mudunuru B.M., Hackl R. The role of microorganisms in gold processing and recovery: A review. Hydrometallurgy. 2014. Vol. 142. P. 70—83.

5. Olson G.J., Brierley J.A., Brierley C.L. Bioleaching review. Pt. B: Progress in bioleaching: applications of microbial processes by the minerals industries. Appl. Microbiol. Biotechnol. 2003. Vol. 63. P. 250—257.

6. Neale J.W., Gericke M., Ramcharan K. The application of bioleaching to base metal sulfides in Southern Africa: Prospects and opportunities. In: Proc. 6th Southern African Base Metals Conf. 2011. P. 367—388.

7. Cobley J.G., Cox J.C. Energy conservation in acidophilic bacteria. Microbiol. Rev. 1983. Vol. 47. No. 4. P. 579—595.

8. Rohwerder T., Gehrke T., Kinzler K., Sand W. Bioleaching review. Pt. A: Progress in bioleaching: fundamentals and mechanisms of bacterial metal sulfide oxidation. Appl. Microbiol. Biotechnol. 2003. Vоl. 63. Р. 239—248.

9. Sand W., Gehrke T., Jozsa P.G., Schippers A. (Bio) chemistry of bacterial leaching — direct versus indirect bioleaching. Hydrometallurgy. 2001. Vol. 59. P. 159—175.

10. Tributsch H. Direct versus indirect bioleaching. Hydrometallurgy. 2001. Vol. 59. P. 177—185.

11. Karavayko G.I., Rossi J. Biogeotehnologia metallov [Biogeotechnology of metals. Practical guidance]. Mosсow: Center mezdunarodni proectov GKNT, 1989.

12. Mineev G.G. Biometallurgia zolota [Biometallurgy of gold]. Mosсow: Metallurgia, 1989.

13. Rodriguez Y., Ballester A., Blazquez M.L. New information on the pyrite bioleaching mechanism at low and high temperature. Hydrometallurgy. 2003. Vol. 71. P. 37—46.

14. Gehrke T., Telegdi J., Thierry D., Sand W. Importance of extracellular polymeric substances from Thiobacillus ferrooxidans for bioleaching. Appl. Environ. Microbiol. 1998. Vol. 64. Р. 2743—2747.

15. Sand W., Gehrke T. Extracellular polymeric substances mediate bioleaching/biocorrosion via interfacial processes involving iron (III) ions and acidophilic bacteria. Res. Microbiol. 2006. Vol. 157. P. 49—56.

16. Yu R.L., Tan J.X., Yang P., Sun J., Ouyang X.J., Dai Y.J. EPS-contact-leaching mechanisms of chalcopyrite concentrates by A. ferooxidans. Trans. Nonferr. Met. Soc. China. 2008. Vol. 18. P. 1427—1432.

17. Fomchenko N.V. Dvuhstadialnoe bakterialno-khimicheskoe okislenie sulfidnikh konzentratov zolota i tsvetnikh metallov [Two-stage bacterial-chemical oxidation of sulphide concentrates of gold and non-ferrous metals]: Abstr. Diss. of PhD. Mosсow: RHTU iмeni D.I. Меndeleeva, 2012.

18. Gusakov M.S. Razrabotka sposoba wiselatsivania sulvidnih konzentratov sernokislimi rastvorami trhvalentnogo zeleza, polusennimi immobizowanoi biomassoi (na primere medno-nikelevogo pirrotinovogo konsentrata Talnahskoi OV) [Development of a method for leaching sulfide concentrates with ferric acid solutions of trivalent iron obtained by immobilized biomass (for example, copper-nickel pyrrhotine concentrate of Talnakh mining plants)]: Abstr. Diss. of PhD. Mosсow: MISIS, 2012.

19. Krylova L.N., Ignatkina V.A. Sostav i fiziko-himitskie svoistva bioreagenta, primenyaemogo dlay wiselasiwania metallov [Composition and physico-chemical properties of the bioreagent used for metal leaching]. Fiziko-technitskie problemi razrabotki poleznih iskopaemih. 2016. No. 6. P. 142—148.

20. Krylova L.N., Wigandt K.A., Adamov E.V., Zheng Zhihong. Dostoinstwa i nedostatki bakterialnogo wichilachiwaniay sulfidnich conzentratow [Advantages and disadvantages of bacterial leaching of sulfide concentrates]. Tsvet. metally. 2013. No. 11. С. 21—26.

21. Fukui K. Role of frontier orbital in chemical reactions. Science. 1982. Vol. 218. No. 4574. Р. 747—754.

22. Pirson R.D. Zhestkie i myagkie kisloti i osnovania [Hard and soft acids and bases]. Uspehi khimii. 1971. Vol. 40. No. 7. P. 1259—1282.

23. Ramachandran K.I., Deepa G., Deepa K., Namboori P.K. Computational chemistry and molecular modeling principles and applications. GmbH: Springer-Verlag, 2008.

24. Solozhenkin P.M. Molecularnoe modelirovanie tionocarbamatov i iсh wzaimodeistwiya s matrizami mednich mineralov i pirita [Molecular modeling of thionocarbamates and their interaction with matrices of copper minerals and pyrite]. Оbogashenie rud. 2014. No. 4. P. 38—44.