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Contenuto archiviato il 2022-11-21

Binding of heavy metals in steelworks waste by suitable control of dumping

Obiettivo


This research has made it possible to grasp better the properties of various waste and steelmaking by-products, which leads 'in fine' to propose a schema for dumping generalizing the use of scoria or slag as a bottom layer both for:

- deposits of natural land for banal industrial waste,
-controlled dumps called class I, in order to protect the surroundings in case of accidental leakage and to generate a leaching agent to be treated less charged with pollutants.
The dumps and tips of integrated steelworks contain considerable quantities of very varied products a number of which contain heavy metals (Pb, Zn, Cr, Ni, Mn, V, etc.) in percentages that vary from one to another. There is a risk of leakage to the environment of these heavy metals, during natural percolation which presents a definite risk for the population, the flora and the fauna, on account of its high ecotoxicity.

The Authorities generally remain very vigilant with regard to the risks of pollution due to heavy metals. A number of directives have already been drawn up by the Community on the subject (74/464/EEC, 4 May 1976) (84/360/EEC, 28 June 1984). The national governments are laying down regulations on the dumping of steelworks waste and co-products which, over the short term, will become economically increasingly restrictive for the profession whenever heavy metals are concerned (the obligation of specialised dumping, preliminary detoxication of waste, etc.).

The regulations that govern the dumping of industrial waste are nevertheless still based on leaching tests only. These tests when applied to heavy metals indicate that leaks are basically due to the initial alkalinity of the product and to the resulting pH. This data is not sufficient to allow assessment of the true leakage of heavy metals from waste dumped because the in-situ percolation may give rise to chemical variations (pH) or physico-chemical variations (forming insoluble phases) which entirely holds up migration of heavy metals.

Preliminary tests performed by the SOLLAC steel company clearly show that the leakage of heavy amphoteric metals can be totally prevented if the deposit consists of products of antagonistic chemical or physical-chemical nature so that none of the heavy metals can pass into the solution during percolation.

The final purpose of this work of research is therefore to define the mixtures of superpositions of steelworks waste produced by integrated steel mills and which do not give rise to leakage of heavy metals when dumped. At the same time, the planned work should lead to a proposal for control of dumping in order to minimise the risks due to heavy metals.

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Coordinatore

Laboratoire d'Etude et de Contrôle de l'Environnement Sidérurgique (LECES)
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Indirizzo
Voie Romaine
57212 Maizieres-les-Metz
Francia

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