Removal of Trace Elements by Cupric Oxide Nanoparticles from Uranium In Situ Recovery Bleed Water and Its Effect on Cell Viability

Summary

Production bleed water (PBW) was treated with cupric oxide nanoparticles (CuO-NPs) and cellular toxicity was assessed in cultured human cells. The goal of this protocol was to integrate the native environmental sample into a cell culture format assessing the changes in toxicity due to CuO-NP treatment.

Abstract

In situ recovery (ISR) is the predominant method of uranium extraction in the United States. During ISR, uranium is leached from an ore body and extracted through ion exchange. The resultant production bleed water (PBW) contains contaminants such as arsenic and other heavy metals. Samples of PBW from an active ISR uranium facility were treated with cupric oxide nanoparticles (CuO-NPs). CuO-NP treatment of PBW reduced priority contaminants, including arsenic, selenium, uranium, and vanadium. Untreated and CuO-NP treated PBW was used as the liquid component of the cell growth media and changes in viability were determined by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay in human embryonic kidney (HEK 293) and human hepatocellular carcinoma (Hep G2) cells. CuO-NP treatment was associated with improved HEK and HEP cell viability. Limitations of this method include dilution of the PBW by growth media components and during osmolality adjustment as well as necessary pH adjustment. This method is limited in its wider context due to dilution effects and changes in the pH of the PBW which is traditionally slightly acidic however; this method could have a broader use assessing CuO-NP treatment in more neutral waters.

Introduction

Approximately 20% of the US electrical supply is provided by nuclear energy and, based in part on national incentives to increase energy independence, US nuclear capacity is expected to increase ¹. Worldwide growth of nuclear energy also is expected to continue, with much of the growth occurring outside the US ². As of 2013, 83% of US uranium was imported, but 952,544 metric tons of reserves exist in the US ^3,4. In 2013 there were 7 new facility applications and 14 restart/expansion applications between Wyoming, New Mexico, and Nebraska ⁵. In the US, uranium is predominately extracted through in situ recovery (ISR) ....

Protocol

All samples were collected at the uranium liquid processing building of a uranium ISR facility in Wyoming.

1. Production Bleed Water (PBW)

1. Collect two types of water samples from an ISR uranium facility: PBW and reverse osmosis (RO) water. Collect PBW from a monitoring tap after the ion exchange process but before reverse osmosis decontamination. Collect RO samples after the PBW is decontaminated by reverse osmosis treatment.
   NOTE: Lixiviant is transported in pipelines from multiple well fields to the uranium liquid processing building, where it is collected in a column and prepared for ion exchange. Approximately 1-3% of....

Results

PBW component concentrations and pH in untreated and CuO-NP-treated PBW are reported in Table 1. Martinson and Reddy (2009), reported that the point of zero charge of the CuO-NP is estimated at 9.4 ± 0.4. Given that the pH of PBW was 7.2-7.4, in these conditions, water donates protons to CuO-NPs, causing the nanoparticle surface to be positively charged allowing for the adsorption of negatively charged species. CuO-NP treatment removed priority contaminants from PBW, including arsenic, selenium, uranium .......

Discussion

Previous studies reported that CuO-NPs removed arsenic from groundwater ^11,13,30,31. This study supports these previous findings and also reports that CuO-NPs remove additional contaminants from PBW. This study also confirms previous reports that CuO-NPs are effective at arsenic removal, despite the presence of other contaminants and potential competing ions ¹¹. Speciation modeling predicted that 97% of vanadium species in PBW are negatively charged, allowing for adsorption to CuO-NPs, and batch tre.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
CuCl2	Sigma	203149
Borosilicate glass balls	VWR	26396-639	6 mm
Nitric Acid	Fisher	A509-P500	Trace metal grade
0.45 μm syringe filter	Fisher	SLHA 033S S
10x EMEM	Fisher	BW12-684F
Fetal Bovine Serum	ATCC	30-2020
L-glutamine	Fisher	BP379-100
NaHCO3	Sigma	S5761
Penicillin/Streptomycin	ATCC	30-2300
0.22 μm vacuum filter unit	Fisher	09-740-28C
HEK293	ATCC	CRL-1573
HEPG2	ATCC	HB-8065
Trypsin	Sigma	SV3003101
MTT	Sigma	M2128
D-penicillamine	Fisher	ICN15180680
96-well plates	Fisher	07-200-92
DMSO	Fisher	D12814
Spectra Max 190	Molecular Devices
Visual MINTEQ version 3.0	KTH Royal Institute of Technology
ICP-MS	Agilent		Details of instruments, models and detection limits were published in Reddy et al., 2013.
IC DIONEX DX 500	Dionex		Details of instruments, models and detection limits were published in Reddy et al., 2013.
VWR Incubator	VWR