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Titel:
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The influence of particle size on leaching of elements from coarse granular materials
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Auteur(s):
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Gepubliceerd door:
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Publicatie datum:
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ECN
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1998
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ECN publicatienummer:
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Publicatie type:
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ECN-C--98-045
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ECN rapport
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Aantal pagina's:
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Volledige tekst:
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62
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Niet beschikbaar.
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Samenvatting:
In the framework of CEN standardization a compliance test for granularmaterials has been formulated, which is divided in four parts covering
different test conditions. The recently added fourth procedure had a particle
size range up to 40 mm. Concern was expressed about the repeatability of this
latter procedure. This prompted an investigation of the effect of different
particle size ranges on the leaching result. The materials studied are MSWI
bottom ash, phosphate slag and crushed cement-stabilized MSWI fly ash. The
particle size ranges studied ranged from 0 - 0.2 mm up to 40 mm. The results
of the study show that the relative standard deviation increases on average
for the three materials from the 0-4 mm, 0-10 mm to the 0-40 mm size
fraction. The frequently voiced notion that upon size reduction leaching
increase has been proven wrong as a general statement. Several elements show
the opposite behaviour: higher leachability from coarser material than from
fine material. This phenomenon is often associated with a change in pH
between coarse and finer size fractions (the coarser being lower in pH).
Phosphate slag shows the most significant particle size effect, which can be
explained by the dense internal structure of slag, which enhances the
particle surface effect. Still the most significant difference does not
amount to more than a factor of 6 between the size fractions 0-4 mm and 0-40
mm. For more porous materials such as MSWI bottom ash, the effect is much
smaller, however with a much higher relative standard deviation for the 0-40
relative to the 0-4 mm fraction. The 0-40 mm size range in the fourth test is
strongly discouraged to enhance robustness and repeatability of the test.
Based on practicality and repeatability, the best size range for the
compliance leach test is 0-4 mm, where the sensitivity to the particle size
distribution is less critical. 4 refs.
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