BACKGROUND The redox potential is a quantitative indicator of the mixed redox potential of all substances in a system, which reflects the relative strength of the redox capacity of the whole system. It is of great significance to delineate the uranium enrichment horizon. The redox potential of sandstone-type uranium deposits controls the geochemical behavior of uranium and other variable valence elements, and is of great significance for accurately delineating uranium-enriched horizons. The potential difference method is used to measure the redox capacity of the sample by means of the oxidant solution, and the magnitude of the potential difference can accurately reflect the reducing ability of the reducing components in the sandstone-type uranium ore sample.

OBJECTIVES To compare the two methods for the determination of the redox potential (ΔEh) of sandstone-type uranium ores.

METHODS ΔEh of sandstone-type uranium ores was determined by two potential drop methods using potassium dichromate and potassium permanganate as oxidants. The effects of the solution medium concentration, oxidant concentration, equilibrium potential time, sample immersion time, and solid-liquid ratio of sample to oxidant solution on the determination of ΔEh were systematically studied. According to the optimal conditions of the two methods, 8 sandstone-type uranium samples were measured.

RESULTS The ΔEh of the potassium dichromate method was between 15mV and 118mV, and the relative standard deviation was between 2.50% and 7.44%. The ΔEh of the potassium permanganate method was between 45mV and 89mV, with the relative standard deviation of 0.89%-1.42%. The two methods had significant consistency in determining the relative level of ΔEh of 8 sandstone-type uranium ore samples, and the correlation coefficient was 0.9882.

CONCLUSIONS The ΔEh of the potassium dichromate potential drop method is more dispersed with a large range, and the difference in reducing ability between samples can be identified more intuitively. The ΔEh of the potassium permanganate potential drop method is more stable. The ΔEh values of sandstone-type uranium deposits measured by two potential drop methods can be used for the division of redox zoning.