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Making waste products inert for the purposes of upgrading or disposal in landfill

Research into inerting industrial wastes has concentrated on samples of wastes produced by the iron and steel industry, which must go through a stabilization process before being discharged. Initially the physicochemical characterization of the wastes was carried out. With respect to polysulphide stabilization, the mineralogical forms zinc oxide and zinc carbonate were found to be sensitive to polysulphide action but ferrite ZnFe(2)O(4) and substituted magnetite displayed no reaction to the sulphur anion. The behaviour of zinc is ambiguous because sulphuration could not be measured. In studying a synthetic sample it was not possible to produce two different sulphuration reactions but it was demonstrated that the granulometry of the compound to be made inert is the most important factor in sulphuration kinetics. The tests performed on the waste demonstrated that the stabilization of heavy metals such as zinc, lead, cadmium, chrome and chrome(VI) using polysulphide solutions was effective. Pilot tests performed on electric furnace dust showed that the quantities of lead found in leachate fell over a period of time and were very small after two month maturity.

Hydraulic binder stabilization results showed the following:
quantities of mobilizable zinc, lead and cadmium in a batch of electric furnace dust fell steeply from 580, 80 and 150 mg/kg respectively to 1, 12 and less than 0.3 mg/kg (these concentrations were below storage site admission thresholds);
for a different kind of electric furnace dust, the leachable quantity of chrome fell from 4500 to 800 mg/kg;
in another case, the quantity of leachable lead fell from 230 mg/kg to less than 10 mg/kg.

Tests on processing waste in a microwave oven showed that it is difficult to obtain good sintering of the waste. The treatment affects the mobility of lead (reduction) and chrome (increase).

Reported by

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