Solidificação/Estabilização (S/E) de Fe, Ni, Sb e V em pastas de cimento contendo um catalisador de equilíbrio (Ecat).

Abstract

One of the main problems faced by industries is the proper management of waste. In the oil industry, for example, huge amounts of spent catalysts in fluidized bed catalytic cracking(FCC), also called Ecat, are produced worldwide. This residue has potentially toxic elements in its composition, such as iron (Fe), nickel (Ni), vanadium (V) and antimony (Sb). The disposal of Ecat without a proper pre-treatment is not tolerable. The use of the solidification/stabilization (S/S) technique of this residue in cement pastes was evaluated and leaching is an important evaluation means of this treatment, used to predict the degree of efficiency in fixing dangerous constituents in the treated waste. The aimof this thesis was to investigate the use of the S/Smethod to immobilize Fe, Ni, Sb and V from Ecat, usinga Portlandcement as binder. Leaching tests were applied according to the Toxicity Characteristic Leaching Procedure(TCLP 1311), using fresh waterand natural sea water,in different pH. Considering thecoprocessing of various residues in the manufacture of cement, the leaching of chromium and its speciation werealso investigated. Pastes were produced using Special ClassPortland cement(CPE) and15% Ecat. The results showed, in its entirety, that the CPE was efficient in immobilizing the evaluated elements (Fe, Ni, Sb and V). The retention percentage in the paste was 94% for Fe;91% for Ni;90% for V and 74% for Sb. It was observed that the element retention rate was higher in fresh water than in sea water or under TCLP 1311 conditions. This behavior was attributed to the attack of salts present in sea water. Despite this, the element retention rates varied between 73 and 85% after leaching in seawater. Concerning to Cr, the anhydrous CPE showed in its composition 48.70 mg kg-1of total Cr and the speciation of Cr in the leachate of the paste produced with CPE showed 1.881mg kg-1of Cr(VI) in TCLP solution and 1.178 mg kg-1of Cr(VI)in fresh water. In seawater, the Cr(VI) concentration was 23.88 mg kg-1, confirming the more aggressive attack of this environment. It was possible to infer that the S/S technique can be used, considering that all leached concentrations were below the limits established by environmental regulations. As for the evaluation of the cement used, the studies carried out confirmed the presence of Cr and Cr(VI). The toxicity of this species emphasizesthe importance of regulations that define thelimitsfor the presence of this and other contaminants in cement