Efficiency evaluation of natural radionuclide extraction from oil sludge

Abstract

This study examines the mechanisms of radionuclide redistribution and phase-specific concentration in the separated low-activity fractions of oil sludge during treatment. Thermal processing of the sludge led to an increase in the specific activity of key radionuclides and promoted their thermochemical redistribution among the solid, aqueous, and oil phases. A diluted sulfuric acid solution containing the non-ionic surfactant OP-10, applied at concentrations exceeding the critical micelle threshold, was employed as a destructive reagent. Radionuclides such as $^{228}\text{Ra}$ and its decay products, $^{228}\text{Ac}$ and $^{228}\text{Th}$, were predominantly concentrated in barium sulfate and gypsum phases, thereby facilitating subsequent disposal due to the minimal volume of solid residue produced (less than 10~mass%) during thermochemical treatment. Compositional and phase-mineralogical analyses of the initial sludge and its separated fractions were conducted using XRD/EDS and XRF techniques. Natural radionuclides and their progeny were primarily associated with the mineral phase, co-precipitated with barium and calcium sulfates. These results provide a foundation for the development of effective disposal strategies for radioactive oil sludge and contribute to improving sanitary, epidemiological, and environmental safety.