Akinetic study of the depyritization of oil shale HCl-kerogen concentrate by Thiobacillus ferrooxidans at different temperatures

Abstract

The results of kinetic studies of bacterial depyritization of HCl-kerogen concentrate of Aleksinac (Serbia) oil shale by the chemolithoautotrophic thionic bacteria Thiobacillus ferrooxidans under discontinuous laboratory conditions at various temperatures (0, 20, 28 and 37 ºC) at a pH of ca. 1.5 are presented in this paper. Low pH prevents the occurrence of the precipitation of iron(III)-ion hydrolysis products on the substrate particles and thereby reduces the process efficiency. Bacterial depyritization is developed as per kinetics of the first order. The activation energy which points to a successive mechanism of pyrite biooxidation, was computed from the Arrhenius plot. The biochemical kinetics indicators point to a high affinity of the bacteria toward pyrite but small values of Vmax, which are probably the result of decelerated metabolic processes due to the low pH value of the environment resp. the large difference of thepHbetween the external medium and the cell interior.

U radu su prikazani rezultati kinetičkih proučavanja bakterijske depiritizacije HCl-kerogenskog koncentrata aleksinačkog (Srbija) bituminoznog škriljca pomoću hemolitoautotrofne tionske bakterije Thiobacillus ferrooxidans u diskontinualnim laboratorijskim uslovima na različitim temperaturama (0, 20, 28 i 37 ºC) pri pH oko 1,5. Nisko pH sprečava nastajanje proizvoda hidrolize gvožđe(III)-jona, koji se talože na česticama supstrata i time smanjuju efikasnost procesa. Bakterijska depiritizacija se odvija po kinetici prvog reda. Iz Arrhenius-ovog dijagrama izračunata je aktivaciona energija koja ukazuje na sukcesivni mehanizam biooksidacije pirita. Pokazatelji biohemijske kinetike ukazuju na visoki afinitet bakterija prema piritu, ali male vrednosti Vmax, što je verovatno posledica usporenih metaboličkih procesa zbog niske pH vrednosti sredine odnosno velike razlike pH između spoljašnje sredine i unutrašnjosti ćelije.