Extraction concentrating of the acid-soluble forms of rare earth elements from oils of the Volga-Ural oil and gas province using rotating coiled columns

Trace elements in oils are the natural markers of the oil origin of and the mechanism of oil genesis. Direct determination of rare earth elements (REE) in crude oils is rather difficult due to their low concentrations (10–6 wt. %). Information about the forms of trace elements in oils is of particular interest. The goal of the study is determination of the content of acid-soluble forms of REE in oils from various fields of the Volga-Ural oil and gas province. Six samples of oils of heavy and medium density and viscosity were analyzed. Extraction of acid-soluble forms of REE was carried out using rotating coiled columns in 0.5 M aqueous solution of nitric acid. Toluene was used to dilute the oils up to the necessary values of the density and viscosity providing the possibility of extraction in the system aqueous acid solution – oil. The content of REE was determined by inductively coupled plasma mass spectrometry on an Agilent 7900 spectrometer. Their content in an acid-soluble form in oil samples under study ranged within 172 – 2173 ng/kg. Such a wide range of values is attributed to the difference in the geology and age of deposit formation. The highest content of acid-soluble forms of REE (2173 ng/kg) was observed in the oil sample from the Novo-Elkhovsky field, whereas the lowest value (172 ng/kg) was measured in the oil sample of the Pioneer field. It is shown that the content of acid-soluble forms of REE depends on tectonic zoning, productive horizons and layers, as well as on the physical and chemical properties of oils. The distribution of acid-soluble forms of light and heavy REE was evaluated. Most of the REE (75 – 99%) determined in the analyzed oil samples are light REE. It is noted that systematization of the data on the properties of oils, geological and geochemical characteristics of the deposits will provide reliable forecasting of the various forms of REE present in oils.

SEPARATION OF P t (IV), P d (II) AND R h (III) FROM CHLORIDE SOLUTIONS BY MULTISTAGE SOLVENT EXTRACTION USING NITROGEN-CONTAINING EXTRACTANTS

The possibility of Pd (II), Pt (IV), and Rh (III) separation from chloride solutions by solvent extraction in rotating coiled columns (RCC) is demonstrated. The reagents most frequently used in extraction of platinum metals were selected as extractants: trioctylamine (TOA), methyltrialkylammonium chloride (MTAA), tributylphosphate (TBP), N, N, N',N'-tetra-re-octyldiglyTOlamide (TODGA). The completeness of extraction of the platinum group metals from individual and mixed hydrochloric acidic and chloride solutions was studied depending on the nature and concentration of the extractant, acidity of the test solutions and other factors. Optimal conditions for the quantitative extraction of metals from model hydrochloric acidic and chloride solutions and subsequent selective separation at the stripping stage are specified. A scheme of multistaged extraction separation of Pd (II), Pt (IV), and Rh (III) from chloride solutions using a 0.05 M solution of MTAA in toluene as a stationary phase in RCC is proposed. The scheme includes extraction of Pd (II) and Pt (IV) ions from a chloride solution (0, 1 M HCl + 30 g/liter NT) into the organic phase with simultaneous separation of Rh(III) remaining in the aqueous phase, and sequential stripping of Pd (II) and Pt (IV) from the organic phase with a 0.01 M solution of thiourea in 0.1 M HCl and a 1 M solution of thiourea in 0.5 M HCl, respectively. The scheme was tested in separation of the platinum group metals from the technological solution of a given composition. The degree of metal extraction with a 0.05 M MTAA solution in toluene and sequential stripping with thiourea solutions is 99.5% for Rh (III), 99.9% for Pd (II), and 97.4% for Pt (IV). The separated water fractions of rhodium and platinum after leaving the column did not contain impurities of other platinum metals whereas the water fraction of palladium contained 0.5% Pt.