Navegando por Autor "Vasques, Isabela Cristina Filardi"
Agora exibindo 1 - 1 de 1
- Resultados por Página
- Opções de Ordenação
Item Arsenite and arsenate removal from contaminated water by precipitation of aluminum, ferrous and ferric (hydr)oxides(Universidade Federal de Viçosa, 2017-06-30) Vasques, Isabela Cristina Filardi; Mello, Jaime Wilson Vargas de; http://lattes.cnpq.br/5528585258437076Arsenic is a metalloid commonly found in mining sites and can be mobilized in water following acid mine drainage. Due to severe consequences of As contamination, the World Health Organization (WHO) recommended 10 µg L -1 as a threshold concentration for As in drinking water. To face As toxicity, several methods to remove it from water have been considered, including co-precipitation with Fe and Al (hydr)oxides. Such compounds have been considered a good alternative to remove As from contaminated water due to strong bindings between them. However, not only the water needs to be efficiently clean, but also the waste generated must be safe to disposal. In this study three Fe:Al molar ratio (100:0, 80:20 and 60:40) were used to synthesize ferrous and ferric (hydr)oxides by precipitation in water containing high concentrations (50 and 500 mg L -1 ) of As (III) and As (V). Mineralogical phases detected by XRD were goethite, lepidocrocite, magnetite, maghemite, gibbsite and bayerite for precipitates from Fe (II) and ferrihydrite, hematite and gibbsite for synthesis with Fe (III). BCR extractants were used in order to evaluate As remobilization from precipitates, including acid soluble, reducible and oxidizable phases. Arsenic associated to Al and adsorbed phases were also assessed by extractions with NH 4 F and KH 2 PO 4 , respectively. Arsenic adsorbed to iron (hydr)oxides represented the major phase among all other extracted phases. It was found that the method was highly efficient for all treatments (> 93 %) in the beginning of the experiment, but efficiency was somewhat lower for treatments in which lepidocrocite and gibbsite were identified in the precipitated phases. In spite of the high efficiency, however, the threshold for drinking water was not attained to the higher concentration of As (III and V). At this high concentration, even the required threshold for effluent discharge was not attained for arsenite in some treatments. In general, the sludges resulting from treatments were considered safe for disposal, except for treatments with arsenite, which were considered hazardous by leaching test. In general, the presence of Al increased the efficiency as well as the stability of the sludge resulting from treatments with Fe (II), but was unfavorable for treatments with Fe (III). In summary, precipitation of Fe (III) in the absence of Al was more efficient to remove As, therefore, treatments in which precipitation of hematite is favored are the most effective to treat As contaminated water ensuring a safe sludge disposal.