GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 215-6
Presentation Time: 2:50 PM


XIONG, Yongliang, Repository Performance Department, Sandia National Laboratories, 4100 National Parks Highway, Carlsbad, NM 88220,

In this work, the measured solubilities of Nd(OH)3(s) in Na2SO4 solutions up to 1.8 mol•kg–1 from our work are combined with the literature solubility data on Nd2(SO4)•8H2O in H2SO4 solutions to develop a Pitzer model to describe the Na+—Nd3+—SO42–—H+—OH system to high ionic strengths, applicable to nuclear waste isolation and recovery of Rare earth elements (REE) from acidic mine drainage.

REE are critical elements, as they are widely used in numerous industries. At the same time, REE such as Nd(III), are used as good analogs to transuranic actinide elements in +III oxidation state in nuclear waste management. In particular, in the field of nuclear waste management, natural groundwaters such as brines associated with salt formations, may contain relatively high concentrations of sulfate, and the interactions between sulfate and actinides are important. As an example, in the Waste Isolation Pilot Plant (WIPP), a U.S. DOE geological repository for defense-related transuranic waste in the bedded salt formations in New Mexico, USA, the sulfate concentrations in the two WIPP brines that are important for performance assessment, i.e., Generic Weep Brine (GWB), and Energy Research and Development Administration (WIPP Well) 6 (ERDA-6), are 0.203 mol•kg–1 and 0.187 mol•kg–1, respectively. In the low level and intermediate level radioactive sulfate liquid waste in Spain, they are very rich in Na2SO4 with SO42– concentrations up to 2.2 mol•kg–1.

Acidic mine drainages with high sulfate concentrations are potentially the new resources for REE, as they have relatively high concentrations of REE. For instance, the acidic mine drainages from Spain have REE concentrations up to ~70 mmol•kg–1, and the acidic mine drainages in coal mines from China have REE concentrations up to ~1 mmol•kg–1. Therefore, the Pitzer model from this work could also be applied for recovery of REE from acidic mine drainages.

A This research is funded by the WIPP programs administered by the Office of Environmental Management (EM) of the U.S. Department of Energy.

B Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2016-6612A