Impact of Variability in Precipitation Patterns on the Geochemistry of Pyritic Uranium Tailings Rehabilitated with Saturated Cover Technology

Abstract

Increasing variability in precipitation patterns is expected to result from climate change in Canada. This effect has the potential to affect the performances of saturated covers in inhibiting acid rock drainage (ARD) and metal leaching (ML) processes. Because ARD and ML may cause the release of deleterious chemical species into the environment, such climate-change-driven impact was investigated using trickle leach columns. The physical, chemical, and mineralogical characteristics of the tailings as well as chemical composition of the leachate were measured before and after the column study. Results from the experiment showed that higher variability in precipitation regimes could enhance leaching of uranium. Leaching ranged from 67.1 to 90.1% of the total amount of U, with greater values associated with higher variability in precipitation patterns. Lower water levels and prolonged drought periods led to higher oxygen fluxes to the U tailings and dissolution of carbonate-bearing minerals. The release of carbonates could have enhanced uranium leaching through the formation of stable uranium-carbonate complexes in solution. Overall, this study shows that water level variation caused by varying precipitation patterns can significantly affect the drainage chemistry of saturated cover systems for which the level fluctuates freely near the tailings–cover interface.

Physico-chemical aspects of uranium extraction for investigation of underground well leaching control systems

“…For compounds of hexavalent uranium, the formation of the uranyl ion 𝑈𝑂 2 2+ is characteristic. Uranyl salts are highly hydrolyzed and have a pronounced acid reaction (pH 0.02M solutions of uranyl is 2.9) [ [1], [4], [9]].…”

“…Further, increase in acidity (up to pH=0.5-0.3) leads to a decrease in the content of 𝑈𝑂 2 𝑆𝑂 4 0 ; [UО2(SO4)2] 2-, since in acidic solutions at pH < 2-1.5 the most stable form of uranium is the uranyl trisulfate anion [UО2(SO4)3] 4-. If the solution is again raised to pH > 2.5, ion polymerization will appear with the formation of tri-and disulfate uranyl dimer [UО2О5(SO4)3] 4-, [UО2О5(SO4)2] 2due to hydrolysis of complex ions, which leads to a significant increase in capacity of anion exchangers [ [4], [10]].…”

“…The analysis of the experience of exploitation of uranium deposits in the Chusar and Syrdarya regions shows the following [4]:…”

“…For the opening of hydrogenous uranium deposits, the injection of biochemical solutions, as well as the pumping of productive solutions, are carried out using vertical wells. According to their purpose, they are divided into the following: technological, observational, control, and special [4].…”

“…1Турганалиев С.Р.,2 Орынгожа Е.Е., 1,3* Орингожин Е.С.,4 Никулин В.В.,1 Алишева Ж.Н.1 әл-Фараби атындағы Қазақ ұлттық университеті, Алматы, Қазақстан 2 Email: e24.01@mail.ru Никулин Владимир Владимирович PhD докторы, Нью-Йорк штаты Бингемтон университетінің доценті, ECE департаменті, PO Box 6000, Бингемтон, Нью-Йорк, 13902-6000. Еmail: vnikulin@binghamton.edu Алишева Жанат Нуркуатовна PhD докторы, Әл-Фараби атындағы Қазақ ұлттық университетінің доцент қ.а., Алматы, Қазақстан.…”