Sulfur recovery from organic molecules such as toxic sulfones is an actual problem, and its solution through the use of environmentally friendly and nature-like processes looks attractive for research and application. For the first time, the possible bioconversion of organic sulfones (benzo-and dibenzothiophene sulfones) to inorganic sulfide under anaerobic conditions with simultaneous biogas production from glucose within a methanogenesis process is demonstrated. Biogas with a methane content of 50.7%–82.1% was obtained without H₂S impurities. Methanogenesis with 99.7%–100% efficiency and 97.8%–100% conversion of benzo- and dibenzothiophene sulfones (up to 0.45 mM) to inorganic sulfide were obtained in eight days by using a combination of various anaerobic biocatalysts immobilized in a poly(vinyl alcohol) cryogel. Pure cell cultures of sulfate-reducing bacteria and/or H₂-producing bacteria were tested as additives to the methanogenic activated sludge. The immobilized activated sludge “enhanced” by bacterial additives appeared to retain its properties and be usable multiple times for the conversion of sulfones under batch conditions.

The effect of the concentration of an oxygen acceptor in the form of a nitrate-containing salt on the rate and mechanism of hydrocarbon degradation (HC) in actual soil samples extracted from wells of 1 to 5 m in depth from areas allocated for future urban development under the influence of bacterial strains belonging to the genus Rhodococcus (R. ruber Ac-1513 D and R. erythropolis Ac-1514 D) is studied. Initial soil samples containing up to 9.8% HC were capable of producing biogas for 59 years under anaerobic conditions, in the absence of an oxygen acceptor, under the influence of methane-forming indigenous microorganisms. At the same time, the content of fire-dangerous methane in gas products ranged from 8 to 36%, which makes housing development in such areas unacceptable without preliminary treatment. To accelerate hydrocarbon degradation by oil-oxidizing bacteria under non-specific oxygen-free conditions, it was proposed to use an electron acceptor, calcium nitrate. The mechanism of hydrocarbon degradation in the presence of Ca(NO₃)₂ through denitrification has been established. It is shown that effect of calcium nitrate studied in the presence of three concentrations (1.25, 2.5, and 5.0%) on denitrification and anaerobic HC degradation was reversely proportional, which may be associated with the inhibition of the denitrification process by high concentrations of Ca(NO₃)₂. In the presence of a minimum concentration of calcium nitrate (1.25%), maximum rates of anaerobic HC degradation in the soil are of k = 1.27 and 0.32 year^–1 during warm and cold seasons, respectively. The content of the main non-flammable reaction product, carbon dioxide in the gas mixture was 99% by volume. Thus, the complete decomposition of the hydrocarbon and the gas generation phase may be completed within 1 year, which is 59 times faster than processes occurring in the absence of an oxygen acceptor.

Due to the presence of environmental problems, it is urgent to improve the processes aimed at the processing and purification of hydrocarbon-containing wastes and wastewaters. The review presents the latest achievements in the development of nanostructured catalysts made from different materials that can be used to purify oil-polluted wastewaters (petroleum refinery wastewater, oilfield-produced water, sulfur-containing extracts from pre-oxidized crude oil and oil fractions, etc.) and eliminate components of hydrocarbon pollutants (polyaromatic hydrocarbons, phenols, etc.). The results of the analysis of possible combinations of chemical and biological catalysts for deeper and more effective solutions to the problems are discussed. The possibilities of highly efficient elimination of hydrocarbon pollutants as a result of the hybrid application of nanoparticles (graphene oxide, mesoporous silica, magnetic nanocatalysts, etc.) or catalytic nanocomposites for advanced oxidation processes and biocatalysts (enzymes, cells of bacteria, mycelial fungi, phototrophic microorganisms and natural or artificial microbial consortia) are analyzed.

This work continues a cycle of studies aimed at developing new approaches to the regeneration of coked bimetallic heterogeneous catalysts. The activities of three Ru-125 (Pt-Re/γ-Al₂O₃) industrial reforming catalyst samples (fresh catalyst (A), catalyst removed from an industrial reactor (B), and sample B after treating it with ozone in supercritical carbon dioxide (SC-CO₂) (C)) are been compared in the reforming of n-heptane. It is established that sample B is deactivated appreciably: the conversion of n-heptane and the yield of reforming products are generally much lower than on the fresh catalyst. After treating it with an O₃/SC-CO₂ mixture, the conversion of n-heptane not only returns to the level of fresh sample A, but also exceeds it by a factor of 1.2. The qualitative composition of the products obtained on samples A, B, and C is nearly the same, but there are some changes in the quantitative ratio of certain products. Regeneration with ozone is found to be promising for further development and scaling.

The selection of a biocatalyst was performed and the first optimal microbial association was obtained. This association was capable of converting products of depolymerization of sawdust, straw, and lignin into volatile fatty acids with an acid-producing activity that was greater by 1.3 times than the initial methane activity. The largest percentages of butyric acid (40%) and ethanol (14%) were obtained from biomass out of straw in concentrations of soluble organic substances from 2.5 to 6.3 g_COD/L. Using biomass from sawdust and lignin at concentrations of organic substances from 4.0 to 8.0 g_COD/L and a duration of the conversion process of up to 18 days we obtained an output of butyric acid that was two times smaller than that on a biomass from straw.