CEN/TR 15018:2005

SLOVENSKI STANDARD
01-maj-2006
Karakterizacija odpadkov – Alkalni razklop vzorca odpadka
Characterization of waste - Digestion of waste samples using alkali-fusion techniques
Aufschluss von Abfallproben mittels Alkalifusion
Caractérisation des déchets - Digestion d'échantillons de déchets par mise en solution
par fusion alcaline
Ta slovenski standard je istoveten z: CEN/TR 15018:2005
ICS:
13.030.01 Odpadki na splošno Wastes in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT
CEN/TR 15018
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
November 2005
ICS 13.030.01
English Version
Characterization of waste - Digestion of waste samples using
alkali-fusion techniques
Caractérisation des déchets - Digetsion d'échnatillon de Aufschluss von Abfallproben mittels Alkalifusion
déchets par Mise en solution par fusion alcaline - Guide de
bonnes pratiques pour la mise en solution par fusion - Les
différentes méthodes et protocoles existants
This Technical Report was approved by CEN on 6 December 2004. It has been drawn up by the Technical Committee CEN/TC 292.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 15018:2005: E
worldwide for CEN national Members.

Contents
Introduction.4
1 Scope.5
2 General information.5
2.1 Digestion of samples.5
2.2 Digestion by fusion.5
3 Fluxes.6
3.1 Alkaline fluxes.7
3.2 Acid fluxes.10
3.3 Oxidising fluxes.11

3.4 Reducing fluxes (alkaline fluxes + reducing agents, sulphides).12
3.5 Digestion by sintering.12
4 The crucibles.12
4.1 Platinum.12
4.2 Silver.13
4.3 Nickel.13
4.4 Vitreous carbon.13
4.5 Iron.13
4.6 Porcelain.13
5 Protocols currently used within industry.13
5.1 Analysis of 16 metallic elements in crushing residues [11] .13
5.2 Determination of Si, Al, Fe, Mn, Mg, Cr, Ti, and F in slags [12] .15
5.3 Fusion with carbonate or borate mixture [15].16
5.4 Fusion with lithium borate [14] .17
5.5 Standards (non exhaustive list) .17
5.6 Fluxes and their applications.18
6 Comparison of different digestion techniques .21
7 Conclusion.23

Bibliography.24

Foreword
This Technical Report (CEN/TR 15018:2005) has been prepared by Technical Committee CEN/TC 292
“Characterization of waste”, the secretariat of which is held by NEN.
This Technical Report is the translation of the French guideline BP X 30-428 "Digestion by fusion – Good practice
guide for digestion by fusion: the different existing methods and protocols" and adoption as a CEN/TR. It gives
information about the digestion of the waste samples using alkali-fusion techniques.
Introduction
EU regulations (e.g. hazardous waste, waste incineration, European waste catalogue) ask in many cases for the
total content of certain elements. In the European landfill directive, knowledge of total composition is given as an
example of waste property-based criteria and is part of the basic characterization of waste.
In these special cases the total content of certain elements has to be determined. The standard based on acid
digestion of waste samples (EN 13656) is in almost all cases applicable. However for some elements or waste
composed of very refractory matrix (e.g. silicates, carbides, oxides), or when some residue is left after acid
digestion, alkali-fusion may be used to bring the waste sample completely into solution.
1 Scope
This Technical Report describes digestion methods for the determination of element contents of waste samples by
using different alkali-fusion techniques.
2 General information
2.1 Digestion of samples
The determination of the elemental chemical composition of waste material includes a pretreatment of the sample
comprising several stages:
 sampling for analysis (drying, crushing, homogenisation, sample reduction);
 digestion.
This last stage of digestion is essential because it allows to obtain a homogenous medium compatible with current
analytical methods (atomic absorption spectrometry AAS, inductively coupled plasma and atomic emission
spectrometry ICP/AES, inductively coupled plasma mass spectrometry ICP/MS, molecular absorption spectrometry
MAS, X-ray fluorescencespectometry XRF).
The diversity of the materials is such that this stage remains very complex and can give rise to major errors due
mainly to:
 contamination of the sample by digestion reagents;
 incomplete digestion;
 loss of elements by adsorption onto the mineralization residue, onto the filter, or onto the walls of the
mineralization reaction vessel;
 loss of elements by volatilisation (over and above those connected with drying and crushing);
 loss by reprecipitation in the form of hardly soluble salts.
Digestion is generally conducted in two stages. The attack, which consists in destroying the sample's organic
matter and in dissolving the mineral residue by possibly modifying the specification by a very aggressive medium,
followed by a dilution of the residue by a liquid allowing to obtain a homogeneous solution compatible with the
subsequently implemented analytical techniques. Specific methods have been developed for volatile elements.
While numerous digestion methods exist, none is universal. The choice depends, on the one hand, on the nature of
the sample (matrix type) and, on the other hand, on the sought after element(s) or on the targeted objective :
determination of the total content or search for exogenous contaminants. Digestion can be performed by a wet
(acid attack) or dry (fusion, calcination, combustion) technique.
The purpose of this code of good practices is to inventory those fusion methods which allow the mineralisation and
digestion of waste for which acid attacks do not give satisfactory results.
2.2 Digestion by fusion
Fusion is often employed for the digestion of mineral materials (silicates, alumino-silicates, .) and more particularly
of certain refractory oxides (zircon, chromite, .), but it is unsuitable for the digestion of volatile elements.
Digestion by fusion requires the use of a specific flux which determines the nature of the reaction involved:
 acid-alkaline reaction:
 alkaline fusion (carbonates, borates, hydroxides);
 acid fusion (disulphates and pyrosulphates, fluorides, boron oxides);
 redox reaction:
 oxidizing fusion (alkaline fluxes + oxidants, peroxides);
 reducing fusion (alkaline fluxes + reducing agents, sulphides).
Fusion is conducted in platinum, porcelain, silver, nickel, iron, vitreous carbon, zirconium, graphite or terracotta
crucibles. The choice of the crucible depends on the nature of the substance to be decomposed and on the type of
flux.
Heating can take place in muffle ovens, induction ovens, tunnel ovens, over flames (Mecker burner) or more
recently in microwave ovens. The time and temperature vary depending on the sample, crucible and flux being
used.
The dilution of the fusion product is generally carried out in water or acidified water (water acidified with
hydrochloric or nitric acid up to 5 % ml/l) which is heated in order to solubilise the solid formed at time of fusion.
3 Fluxes
Several types of salts or other chemicals are proposed for the fusion of rock samples: alkaline borates, sodium
carbonate (Na CO ), sodium hydroxide (NaOH), sodium peroxide (Na O ), equivalent potassium compounds,
2 3 2 2
potassium pyrosulphate (mixture of K S O and KHSO ), alkaline fluorides (e.g. : KHF ). These fluxes have
2 2 7 2
specific applications.
In general, the efficiency of a flux for attacking silicate rocks increases from Na CO < NaOH < Na O . Table 1
2 3 2 2
gives a non exhaustive list of the fluxes together with their melting point and the generally used crucibles.
Table 1 — Fluxes used for the fusion of silicate rocks
Salt Melting point (°C) Fusion crucible
Lithium metaborate LiBO 845 Pt + 5 % Au
Lithium tetraborate Li B O 930 or graphite
2 4 7
Sodium carbonate Na CO 851 Pt or Ni
2 3
K CO
Potassium carbonate 891
2 3
a
Sodium hydroxide NaOH Zr (or Au, Ni, Ag)
318, 314
Potassium hydroxide KOH 360
Na B O
Sodium tetraborate (borax) 741
2 4 7
a
Sodium peroxide Na O Zr
480 d, 675
2 2
Potassium superoxide KO 380
a
Potassium fluoride KF
846, 856
a
Potassium hydrogen fluoride KHF
225 d, 239
a
K S O
Potassium pyrosulphate
300, 414
2 2 7
a
Sodium pyrosulphate Na S O
2 2 7
a
Lithium carbonate LiCO
a
Cesium carbonate CsCO
a
NaKCO
Sodium Potassium carbonate 500
a
Ammonium hydrogen sulphate NH HSO
4 4
a
Sodium hydrogen sulphate NaHSO
a
KHSO
Potassium hydrogen sulphate
a
Ammonium hydrogen fluoride NH HF
4 2
a
Sodium nitrate NaNO
a
Potassium nitrate KNO
a
d : decomposes.
3.1 Alkaline fluxes
3.1.1 Carbonates
Fusion using sodium carbonate is the most generally employed method of attack for the digestion of silicates (rocks
and glasses). One can use either sodium carbonate which melts at 850 °C, or a mixture of potassium carbonate
and sodium carbonate in equal parts, an eutectic mixture which melts at 700 °C. Sodium and potassium carbonate
(NaKCO ) has a melting point of 500 °C.
Potassium carbonate is rarely used alone. Mixed with sodium carbonate, it is used for analysing silicates because
the fusion temperature is lower than that of the sodium carbonate alone. This mixture can therefore be used for the
determination of volatile elements such as chlorine, fluorine.
Sometimes a little nitrate is added in order to stimulate the oxidation of chromium for example.
Fusions using carbonates generally take place in platinum crucibles at 900 °C. These fusions shall be performed
preferably in an inert atmosphere in order to limit the formation of soluble sodium platinate.
Conversely, when the sample under analysis contains iron, the fusion shall be conducted maintaining an oxidising
atmosphere inside the crucible in order to prevent the re
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