Physical and Chemical Interactions Affecting U and V Transport from Mine Wastes

Author

Sumant AvasaralaFollow

Publication Date

Spring 3-2-2018

Abstract

This research investigates the physical and chemical interactions that affect the transport of uranium (U) and vanadium (V) from uranium mine waste sites by integrating laboratory experiments and reactive transport modelling with various spectroscopy, microscopy, and diffraction techniques. The document consists of results from three related studies. In the first study (Chapter 3), the reactive transport of U and V was investigated by sequentially reacting mine wastes collected from Blue Gap/Tachee Claim-28 mine site, AZ with 10mM NaHCO₃ (7.9) and 10mM CH₃COOH (3.4) during continuous flow through column experiments. Under both of these conditions (pH 3.4 and 7.9), dissolution of U-V bearing minerals predominant at the site were identified as a key mechanism affecting the reactive transport of U and V. The equilibrium (K_eq) and reaction rate constants (k_m) for U-V bearing mineral dissolution were estimated to be K_eq = 10^-44.81 and k_m = 4.8x10^-13 mol cm^-2 sec^-1 at circumneutral conditions, and K_eq = 10^-38.65 and k_m = 3.2x10^-13 mol cm^-2 sec^-1 under acidic conditions. These results, coupled with electron microscopy data, suggest that the release of U and V is affected by difference in solution pH and crystalline structure of U-V bearing minerals. Identifying the crystal chemistry of these U-V bearing minerals was the task in the second study (Chapter 4) of the dissertation. Using various diffraction and microscopy tools, the U-V bearing minerals were identified as hydrated carnotite.

Finally, the mobility of U from co-occurring submicron U(IV) and U(VI) mineral phases in mine wastes from the Jackpile mine in Laguna Pueblo, NM was investigated under oxidizing conditions. Co-occurrence of U(VI) and U(IV) at a 19:1 ratio mostly as coffinite (USiO₄) and U-phosphate was observed in these mine waste solids. The highest U release from these mine wastes was observed during batch reactions with 10 mM NaHCO₃ solution containing ambient dissolved oxygen concentrations. Results from these investigations provide an improved understanding on the role of thermodynamics, crystallinity, stoichiometry, and solution chemistry in the reactive transport of U and V from mine wastes that affect the water quality of surface and ground water resources.

Keywords

Uranium, Vanadium, transport, uranyl vanadate, reactivity, dissolution, column experiments

Document Type

Dissertation

Language

English

Degree Name

Civil Engineering

Level of Degree

Doctoral

Department Name

Civil Engineering

First Committee Member (Chair)

Dr. Jose M. Cerrato

Second Committee Member

Dr. Ricardo Gonzalez Pinzon

Third Committee Member

Dr. Bruce Thomson

Fourth Committee Member

Dr. Adrian Brearley

Fifth Committee Member

Dr. Mehdi Ali

Recommended Citation

Avasarala, Sumant. "Physical and Chemical Interactions Affecting U and V Transport from Mine Wastes." (2018). https://digitalrepository.unm.edu/ce_etds/205