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A New, Safe, Rapid Digestion Method For Uranium Exploration Using ColdBlock™ Digestion TechnologyKirill Pereverzev, Director of Technology and Business Development, ColdBlock Technologies Inc. and Dr. Matthew Leybourne, Associate Professor Geochemistry, Department of Earth Sciences, Laurentian University

INTRODUCTION Uranium production and the nuclear industry is important to Canada. Current digestion techniques are problematic. ColdBlock Digestion and its technology offer a safer and effective alternative. The dissolution is very rapid, taking only 10 minutes (or less) and the resultant solution is easily processed through spectroscopic analysis.

Results obtained using the ColdBlock Digestion technology were comparable to the certified values from CANMET and Geostats with near 100% recovery. It was postulated that samples where recovery was below 100% were of a matrix that was resistant to the inverse aqua regia treatment. This was supported when consulting the certificate of analysis and identifying that both the Geostat and CANMET certified values were derived using total digestion techniques rather than a leach. This was further examined when looking at the behavior of the geological samples submitted by a uranium producer.

Digestion of the submitted geological samples was initially done using the same leaching method as for the CRMs. The analytical results from this method were then compared to those of the certified values provided for a partial digestion. It was observed that the values were consistently elevated above 100%. This outcome was initially seen as a possible contamination issue however this was dismissed when new test tubes were used and produced similar results. The proposed explanation was that because of the increased power of the 6-channel digester, the aqua regia leach could reach more resistant elements and hence higher recoveries were observed.

In addition to the partial digestion certified values, the geological samples were also submitted with total digestion values based on a three-acid digestion protocol including hydrofluoric, perchloric, and nitric acids. To assess ColdBlock recoveries, and compare to this three-acid digestion value, a method was employed as described by Helmeczi et al.2 The values obtained were very consistent, albeit higher than the certified values, which led to recoveries between 140% to 200%. These recoveries were attributed to the effectiveness of the phosphoric acid treatment as it was previously described as being able to dissolve chromite species as well as most rare earths.

ColdBlock-based digestions for uranium showed comparable results to existing techniques while using a safer acid matrix and demonstrating significantly faster digestion time. Future work will be focussing on expanding the application of ColdBlock Digestion technology.

Associates

METHODS AND RESULTS SUMMARY AND DISCUSSIONColdBlock digestion is a versatile and safer technology. Helmeczi et al.2 demonstrated that through a selective application of phosphoric acid, a near 100% recovery of rare earth elements could be achieved. The same study2 also highlighted the recovery of Uranium and Thorium. Building on the findings of Helmeczi et al.2 this study focussed on Uranium-bearing CRMs, as well as geological samples provided by a uranium producer in Saskatchewan.

The analysis was performed using two analytical instruments:n Agilent 5100 ICP-OESn Perkin Elmer DRC Elan DRC II

The certified reference materials and samples were treated using two different methods:

Treatment Option 1n 12 mL Inverse Aqua Regian 3:1 ratio of HNO3:HCln 0.2 g to 1.0g of sample sizen 10 minutes’ digestion

Treatment Option 2n 10 mL Phosphoric acidn 0.2 g of samplen 10 minutes’ digestion

Comparable results were obtained using the ColdBlock technique when compared with the certified values from CANMET and Geostats with near 100% recovery, as well as with samples from the uranium producer. ColdBlock-based digestions for uranium are shown to be comparable to results obtained with current techniques while using a safer acid matrix and requiring significantly less digestion time.

Digest ion Technology

In order to analyze a geological sample, the solid sample must first be converted (digested) into a form that can be analyzed by an analytical spectroscopy system. Several digestion techniques are available to an analyst consisting of primarily two groups: fusions and acid digestions.

Fusions:

n Use solid reagents, called fluxes, to allow total liquefaction of the sample.

Acid Digest ion:

n Works by using acids to dissolve minerals and stabilize ions in an aqueous solution.

n Dissolution speed is accelerated with the application of heat. Heat flows to the acid and sample by conduction and convection when using hotplates or hotblocks. To improve heating efficiency and speed, microwave ovens were used to harness the efficiency of microwave radiation to heat the acid and sample. This was met with limited success due to the need to pressurize the reaction vessel.

ColdBlock Digest ion:

n Realizing the problems with the current acid digestion technologies, ColdBlock Technologies developed a novel way to transfer the heat efficiently, allowing the sample particle to accept much of the heat before the acid medium. Using a shortwave infrared lamp as the heat source, the radiation would pass through the reaction vessel and acid and be absorbed by the sample particle allowing for unprecedented digestion speeds.

n In addition to the infrared heat source, the technology also employs a heat exchanger mechanism to improve the recovery of the acid being volatilized due to the superheated sample particles in solution.

Uranium production allows for ongoing growth in the nuclear industry and Canada is currently a world leader in the production and processing of this strategic and critical resource. Current acid digestion techniques use dangerous acids including hydrofluoric (HF), perchloric (HClO4), and sulphuric acid (H2SO4). Fusion techniques generate high total dissolved solids that are difficult to analyze with existing spectroscopy systems. As such, technological advances eliminating these issues will help Canada remain a major player in the uranium industry. ColdBlock Digestion, a Canadian-made and invented technology, offers an alternative to the current problematic methods by dissolving uranium in a phosphoric acid matrix using shortwave Infrared (IR) light in only 10 minutes. The resultant solution is easily processed through spectroscopic analysis.

We compared ColdBlock digestions of several uranium bearing Certified Reference Materials (CRMs) obtained from CANMET, Geostats, and a uranium producer to existing values that were obtained using two acid leach, four acid total, and XRF fusion techniques.

86%106% 104% 101%

83%97%

0%

100%

GU-03 GU-08 GU-10 GU-11 RL-1 BL-5The graph illustrates the % recovery of Uranium from the examined CRMs using an inverse Aqua Regia treatment. The measured values obtained using ColdBlock Digestion were compared to certified values that were obtained using 4-Acid digestion, fusion, and Instrumental Neutron Activation Analysis (INAA) as indicated by the respective certificate of analysis. The values were collected in triplicate and the error bars represent a standard deviation.

Geological Samples Recovery of uranium after an inverse Aqua Regia leach and phosphoric acid digestions

CRM Samples Recovery of uranium after an inverse Aqua Regia leach digestion

1. “Uranium In Canada | Canadian Uranium Production - World Nuclear Association”. World-nuclear.org. N.p.,2016. Web. 13 Sept. 2016.

2. “A novel methodology for rapid digestion of rare earth element ores and determination by microwaveplasma-atomic emission spectrometry and dynamic reaction cell–inductively coupled plasma-massspectrometry”. Helmeczi E, Y. Wang and I.D. Brindle. Talanta 2016 (160); 521-527.

AcknowledgementsDr. Matthew Leybourne, Laurentian UniversityErick Helmeczi, Brock UniversityLorie-Anne Doig, ColdBlock Technologies

www.coldblock.ca 1-888-428-2855

Agilent Technologies

IR lamps emithigh energyto energize

particles directlyAchieves digestionin 10-15 minutes

Excellent andaccurate recovery

of elements

A coldblockpromotes

condensation

Canadian Uranium Production1

YUKONTERRITORY

NORTHWESTTERRITORIES

VICTORIAISLAND

NUNAVUT

BRITISHCOLUMBIA

ALBERTASASKATCHEWAN

MANITOBA

ONTARIO

QUEBEC

NEWFOUNDLAND

NEWBRUNSWICK

NOVA SCOTIA

YUKONTERRITORY

NORTHWESTTERRITORIES

VICTORIAISLAND

BAFFINISLAND

NUNAVUT

BRITISHCOLUMBIA

ALBERTASASKATCHEWAN

MANITOBA

ONTARIO

QUEBEC

NEWFOUNDLAND

NEWBRUNSWICK

NOVA SCOTIA

BAFFINISLAND

VancouverEdmonton

SaskatoonWinnipeg

Toronto

Montreal

Port Radium

Beaverlodge

Cluff Lake

Cigar Lake

Elliot LakeBancroft

Midwest Project

McLean Lake

Rabbit LakeMcArthur River

Key Lake

Blind River

Bruce

Pickering

Port HopeDarlington

Gentilly 2Point Lepreau

Port Radium

Beaverlodge

Cluff Lake

Cigar Lake

Elliot LakeBancroft

Midwest Project

McLean Lake

Rabbit LakeMcArthur River

Key Lake

Blind River

Bruce

Pickering

Port HopeDarlington

Gentilly 2Point Lepreau

Nuclear Power Plant

Uranium Fuel Cycle

Former Mine

Proposed Mine

Uranium Operating Mine

Uranium In Canada | Canadian Uranium Production - World Nuclear Association. World-nuclear.org. N.p., 2016. Web. 13 Sept. 2016.

Concentration (ppm)

Sample A 3.17

Sample B 0.64

Sample C 0.36

0.00

1.00

2.00

3.00

Con

cent

ratio

n (p

pm)

Measured Concentrationof Uranium

% Recovery of UraniumVs Certified Value

% R

ecov

ery

Concentration (ppm)

Sample A 130%

Sample B 130%

Sample C 132%

0%

100%

The same inverse Aqua Regia treatment was used to digest the geological samples. The measured values were compared to provided certified values. The certified values had been obtained using an Aqua Regia digestion. The values were collected in triplicate and the error bars represent a standard deviation.

Measured Concentrationof Uranium

Con

cent

ratio

n (p

pm)

Concentration (ppm)

Sample A 10.0

Sample B 3.38

Sample C 1.83

0.0

2.0

4.0

6.0

8.0

10.0

% Recovery of UraniumVs Certified Value

% R

ecov

ery

Concentration (ppm)

Sample A 142%

Sample B 199%

Sample C 169%

0%

100%

200%

The geological samples were provided with two certificates of analysis, an acid leach consisting of nitric and hydrochloric acids, and a three-acid digestion consisting of nitric, perchloric, and hydrofluoric acids. To compare the 3-acid digestion values, it was opted to use the method described by Helmeczi et al. 3 (ie, phosphoric acid to dissolve the sample and later dilution with 2% nitric acid). The phosphoric acid digestions were performed in triplicate, with error bars indicating a standard deviation.