Remoção de metais pesados em lixiviados para uso como fertilizantes
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abstract
The aim of this work is to offer a sequence of processes to convert leachate liquid stream with a highly variable composition, collected from the composting line of a mechanical and biological treatment facility, into commercial fertilizers, which fit the composition requirements of the European Legislation. The leachate was first characterized by total organic carbon (TOC), density, fixed and volatile solids, nutrients as organic and ammoniacal nitrogen, phosphorus, potassium, and heavy metals content, to verify the accordance with the European Legislation for fertilizers. The preliminary characterization showed that the leachate contains low levels of organic and ammoniacal nitrogen and phosphorus but high contents of potassium and TOC, which are interesting to fertilizing purposes, and chromium, which needs to be removed to fit the specifications. To chromium removal, some adsorbents materials were proposed: activated carbon produced from the compost of the referred company and acid activated clays obtained from a partnership with a Kazakhstan institution. The results after the adsorption process showed an interaction between the adsorbents and TOC, which was not intended, and a reduction in the heavy metals content, more efficient for Pb, Cd, Zn and Cu, but less for Cr removal. For future work, the study of the use of ionic resins was proposed through the development of an experimental design, in order to obtain the optimized parameters for the minimization of TOC loss, and promotion of heavy metals removal, especially chromium, using a response surface methodology.
