peroxide fusion powerful and safe dissolution of mining samples for aa and icp analysis[1]

Peroxide Fusion: Powerful and Safe Dissolution of Mining Samples for AA

and ICP Analysis

Luc Bérubé, M. Sc. Chemist

Sales and Services Manager

Philippe Daigle, M. Sc. Chemist

Technical Representative

CMA 2008, Bathurst

© All rights reserved

Claisse 2008 2

Presentation Overview

Standard dissolution methods vs peroxide

fusion

Chemistry of peroxide fusion

Choice of crucible

Application examples

Peroxide fusion vs borate fusion

Peroxide fusion on automated fusion machines


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Standards dissolution methods for mining samples

Hot plate or micro-wave acid digestion

Multi-step, multi-reagent methods

Manipulation of HF (threat to human health-bones)

and sometimes HClO4 (explosive)

Use of high pressure vessels

Usually long (1h and more)

Method is matrix dependant

Difficulty to obtain total dissolution


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Chemistry of Peroxide Fusion

Chemical formula: Na2O2

Chemical structure:

Melting point: 460°C

O Na

Na O


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Chemistry of Peroxide Fusion

Oxidation:

Reaction in solution:

Acidification

OONaONa 2460CT

22 EE

)()(22 22 aqaq OHEONaOHEOONa

)(2

2)( 2 aqs EOHHEO


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Zr or Ni Crucibles?

Temperature must not exceed 525°C


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Peroxide Fusion Application (FeSi)

1. Weigh 0.5g sample, 8 g Na2O2 and 2g of Na2CO3 on top into a zirconium crucible.

2. Heat slowly to avoid a violent reaction and sputtering.

3. Rise the gas pressure. The melt should be red hot.


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4. Once the oxidation reaction is ended, the melt cool down to ambient temperature.

5. The zirconium crucible is then immerged into a water solution. The liquid level must cover the crucible.


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6. When the decomposition reaction stop, add successively two portion of 10 ml of HCl to dissolve the hydroxides and acidify the solution.

7. Boil the solution to totally decompose the peroxide then complete to volume.


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Peroxide Fusion Applications

1. Chromium ores

2. Precious metals (Pt, Pd, Rh)

3. Niobium – Tantalum

4. Beryllium Aluminum Silicate

5. Silica rocks

6. Chromites

7. Ferro-chromium and other ferroalloys

8. Ferro-silicon, silicon, silicon carbide

9. Magnetite, illmenite, rutile

10. Other alloys and steels


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Advantages of Peroxide Fusion


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Peroxide vs Borate Fusion for AA/ICP Sample Preparation

Borate fusion Peroxide fusion

Crucible Pt-5%Au Zirconium

Fusion + Dissolution time 10-12 min. 15-30 min.

Sample matrix type oxides (rocks, zeolithes, cement…)

Reduced samples need

oxidizer.Carbides and

nitrides difficult.

Same as borate fusion.

Easy for metallic and reduced

materials.Carbides and

nitrides.

Temperature 900-1050°C Max 500°C

Fluxes used Lithium borate Sodium peroxide

Retention of volatiles Moderate Good


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Instrumentation for Peroxide Fusion

Bunsen burner

Ovens

Opened system automatic fusion machines


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Peroxide Fusion on Claisse Peroxide


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Conclusion

Peroxide fusion is a powerful technique that

allows the dissolution of many difficult

samples

Peroxide fusion is simple and safe

Peroxide fusion can be performed in opened

system fusion machines to increase safety,

result consistency and throughput

peroxide fusion powerful and safe dissolution of mining samples for aa and icp analysis[1]

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