Wastewater treatment and recovery of uranium by iron and aluminium (hydr)oxides

• Ano de defesa: 2017
• Autor(a) principal: Ferreira, Vanessa de Paula
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa; Solos e Nutrição de Plantas
• Palavras-chave em Português: Urânio; Águas minerais sulfurosas; Minerais de argila; Ciência do Solo
• Link de acesso: https://locus.ufv.br//handle/123456789/29344

Uranium (U) mining and its enrichment process can cause environmental contamination and others problems, especially when acid mine drainage (AMD) occurs. Studies in literature demonstrates the iron (Fe) (hydr)oxides efficiency to immobilize soluble U. However, changes in redox conditions may compromise the efficiency of some minerals, since the ferric hydroxides are unstable under low redox potential (Eh). On the contrary, aluminium (Al) is stable in such environments and could enhance the stability of Fe (hydr)oxides. In this study, the soluble U immobilization was evaluated by the co-precipitation with Fe and Al (hydr)oxides in a U contaminated water. The U recovery and stability in the solid phase were also studied. Solutions of ferric and ferrous sulfate, Al sulfate and a U standard solution were mixed in different proportions in order to obtain 21 treatments, which consisted of a combination of three Fe: Almolar ratio (100:0, 80:20 and 60:40), two valence states of Fe (Fe 2 + and Fe 3 + ) and one more treatment only with Al (Fe:Al = 0:100), in three concentrations of U(80, 40 e 20 mg L -1 ). The synthesis lasted 84 days. The pH solution was measured and adjusted to 9 weekly, as well as the sampling of supernatant sample collections. U, Fe and Al concentrations were determined by ICP-OES. The solid phase was characterized by X-ray diffraction (XRD) and the U remobilization potential in the solid phase evaluated discrete extraction and a leaching test. Results demonstrated that all treatments were efficient to immobilize soluble U in the first 24 hours of incubation. In the end of the incubation period, treatments in the presence of Al were more efficient (more than 95%) than the ones only in the presence of Fe. Besides, treatments in the presence of Al only were not as efficient as the ones in the presence of both Al and Fe. The dominant mineralogical phases formed were magnetite and hematite, in the absence of Al and in the presence of Fe 2+ e Fe 3+ , respectively; goethite in the presence of Al and Fe 2+ ; ferrihydrite in the presence of Al and Fe 3+ and gibbsite in the presence of Al and in the absence of Fe. Magnetite, hematite and gibbsite were less stable compared to goethite. Leaching test and discrete extractions procedures confirmed the need of an appropriated mine waste storage facility for the sludge produced by water treatment and a possible U recovery is also suggested, for example, to its enrichment process.