Sulfur is present in crude oil and petroleum products in the form of various compounds: mercaptans, hydrogen sulfide, sulfides, disulfides, thiophene derivatives, high-molecular-mass heterocyclic compounds, etc. The content of elemental sulfur in petroleum feedstock is low (up to 0.1%). Sulfur negatively affects the service and transportation properties of oil; therefore, the content of sulfur compounds in petroleum products and commercial oil is strictly limited. Numerous methods are used today for removing sulfur compounds from petroleum feedstock, such as hydrotreating, bio- and oxidative desulfurization, extraction, including supercritical fluid extraction, adsorption, alkylation, etc. This review deals with the use of extraction methods for treating petroleum feedstock to remove various sulfur-containing compounds. Particular attention is paid to papers dealing with the use of cheap and available polar organic solvents and inorganic chemicals for removing sulfur and its compounds both from model solutions and from crude oils and petroleum fractions. Also, search for new “green” solvents such as ionic liquids and eutectic mixtures, allowing removal of sulfur compounds from crude oil, shows promise. As a rule, complete removal of sulfur-containing compounds from oil samples by extraction requires a multistep extraction process.

The development and use of instrumental methods for the determination of a wide range of trace elements in oil is considered. Special attention is paid to methods of the direct introduction of...

Study on the behavior and fate of nanofertilizers in soil plays a key role in the assessment of the efficiency of their use for intended purposes. The behavior of nanoparticles (NPs) in soil depends on environmental scenarios, such as Wetting-Drying cycles (WDCs). In the present work, the mobility and fate of CeO₂, ZnO, and Cu NPs in agricultural soil at sequential WDCs have been studied. It has been shown that the mobility of CeO₂ and ZnO NPs decreases after each WDC. After four WDCs the relative amount of CeO₂ and ZnO NPs leached from soil decreases from 0.11 to 0.07% and from 0.21 to 0.07%, correspondingly. The decrease in the mobility of NPs is caused by their immobilization by water-stable soil aggregates, which are formed at sequential WDCs. Cu NPs are dissolved by soil solution, so their mobility (in ionic forms) increases after each subsequent WDCs. The relative content of Cu²⁺ sourced from Cu NPs increases up to 0.88% after four WDCs. It has been found that mineral NPs of soil can play an important role in the transport of insoluble engineered NPs. As for soluble NPs, the kinetics of their dissolution governs their mobility in ionic forms.

A flow-through method is proposed for the separation of sulfur compounds from sulfur and sour crude oils by solvent extraction using centrifugal extractors. The effectiveness of using various organic (tetrahydrofuran, pyridine, methanol, ethanol, acetone, dimethylformamide, and acetonitrile) and inorganic (mineral acids, NaOH) extractants for the extraction of sulfur-containing compounds from crude oils of the Ashal’chinskii and Romashkinskii deposits is estimated. It is shown that methanol and dimethylformamide are most effective for extracting sulfur from crude oils. The use of additional sample preparation, which consists in the ultrasonic and/or magnetic processing of oil in combination with its oxidation and heating, increases the efficiency of extraction of sulfur-containing compounds by 20–40%. It is shown that the choice of extractant composition for the extraction of sulfur compounds is determined by the physicochemical properties and composition of the oil.