Sequential extraction for evaluating the behaviour of selected chemical elements in light weight aggregates manufactured from mining and industrial wastes

The chemical extraction of twenty-nine elements in a washing aggregate sludge, a clay-rich sediment, a sewage sludge, the mixtures of these materials and the artificial lightweight aggregates [LWAs] manufactured with them was determined by applying the optimized European Community Bureau of Reference sequential extraction procedure in order to establish the effect of the thermal treatment on the extraction of the selected elements. In accordance with the UNE-EN-1744-3 standard [2003], which states a single extraction procedure, preparation of eluates by aggregate leaching was also carried out. All the elements are mainly associated with the residual fraction in the LWAs so their availability is relatively low. The element that presented the highest concentration in the eluates after completion of the single extraction procedure was Fe. All the studied elements are in concentrations below the limit values for inert wastes so, from the standpoint of chemical leaching, the studied LWAs may be used in lightweight concrete manufacturing

Heavy metal chemical fractionation and immobilization in lightweight aggregates produced from mining and industrial waste

The fractionation of five heavy metals in a washing aggregate sludge, a sewage sludge, a clay-rich sediment, the mixtures of these materials and the lightweight aggregates manufactured with them has been determined by applying the optimized European Community Bureau of Reference sequential extraction procedure in order to evaluate the effects of the heating process on the extraction of these elements. Additionally, preparation of eluates by aggregate leaching has been performed in accordance with the UNE-EN-1744-3 standard. The availability of all the studied heavy metals has been reduced by the thermal treatment, since most of the heavy metals have become part of the undigested material in the lightweight aggregates. Nickel has been the heavy metal that has presented the highest concentration in the eluates obtained after completion of the single extraction procedure in the lightweight aggregates. The studied lightweight aggregates may be used in lightweight concrete manufacturing from the standpoint of heavy metal leaching