Valorización de residuos industriales en el desarrollo de técnicas de tratamiento innovadoras en la recuperación de suelos contaminados en la Región de Murcia

Abstract

The present thesis, which follows the format of a selection of publications, looks at two aspects of risk analysis associated with land use changes involving soils contaminated with ETPs - the characterisation of these soils as a result of mining and industrial activities, and the techniques that may be applied to recover the same. We describe an in situ immobilisation experiment using the sludge resulting from cutting marble on material of mining origin (Portman Bay) and with the industrial wastes from a Chemical Industry (Escombreras). The residues used (marble sludge), which have a high calcium carbonate content, high pH and and fine granulometry, can in this way be reused and given extra value since the results obtained can be considered excellent. Heavy metal mobilisation in different situations is related with metal speciation and studies are necessary to evaluate the risks involved. In this respect, three aspects should be emphasised: - The evaluation of the potential and natural mobility of sediments of mining origin through in vitro speciation studies and selective and sequential extractions. DRXD and SEM-EDX techniques were used to study the wastes after treatment to assess the effectiveness of the speciation test. - The importance of knowing the bioavailable values of the ETPs for realising the correct evaluation of the risk of ingestion by humans and the relation between these values and the mineralogy of the soils. - The formation of outcrops as a consequence of acid mining drainage that may represent a danger due to the high solubility and bioavailability of the ETPs they contain. We use the MINTEQ model to evaluate the same. The results for the toxicity of the leachates obtained in the immobilisation experiments in columns provide an estimate of the capacity of marble sludge to immobilise metals and reduce sediment toxicity. Treatment with calcium carbonate-rich wastes is viable for producing stable compounds with the metals and for reducing the risk for the biotic ecosystem, as confirmed by the results of the bioassays carried out using the Microtox method. This method is valid for evaluating the toxicity of the leachates generated in the different phases but it does not identify the cause of the toxicological problem, which might be the high concentration of metals, acidity, high saline concentration, etc.. for this reason other, complementary diagnostic methods must be applied. The stabilisation/immobilisation of heavy metals using calcium carbonate-rich wastes was very effective and the toxicity of the leachates of the treated wastes disappeared. The EC50 presented a direct relation with the concentration of the soluble metals and acidity in the samples.