Combined mineralogical and EXAFS characterization of polluted sediments for the definition of technological variables and constraints

An extremely severe aspect, both from environmental and economic viewpoint, is the management of pollutedsediments removed from drainage and irrigation canals. Canals, in order to retain their functionality over the time,need to have their beds, periodically cleaned from sediments there accumulating. The management of removedsediments is extremely demanding, also from an economical perspective, if these latter needs to be treated asdangerous waste materials, as stated in numerous international standards. Furthermore the disposal of such a largeamount of material may introduce a significant environmental impact as well. An appealing alternative is the recoveryor reuse of these materials, for example in brick and tile industry, after obviously the application of appropriatetechniques and protocols that could render these latter no longer a threat for human health. The assessment ofthe effective potential danger for human health and ecosystem of sediments before and after treatment obviouslyrequires both a careful chemical and mineralogical characterization and, even if not always considered in the internationalstandards, the definition of the coordination shell of heavy metals dangerous for human health, as afunction of their oxidation state and coordination (e.g. Cr and Pb), and introducing technological constraints oraffecting the features of the end products. Fe is a good representative for this second category, as the features ofthe end product, such as color, strongly depend not only from Fe concentration but also from its oxidation state,speciation and coordination. This work will first of all provide mineralogical characterization of sediments fromvarious sampling points of irrigation and drainage canals of Po river region in the north-eastern of Italy. Sampleswere investigated with various approaches including X-ray powder diffraction under non-ambient conditions, thermalanalysis and EXAFS spectroscopy. Obtained results, and in particular EXAFS spectra were used to define andoptimize the technological variables of the recovery process.