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25. Uso de Arcillas Especiales para Depuración de Aguas Residuales

Author

Andrade, L., Covelo, E.F., and Vega, F.A.

Subjects
wastewater treatment, clay adsorption, heavy metals, environment
Abstract

Para evaluar la eficacia de las arcillas especiales para la remoción de metales pesados de aguas residuales, se muestrearon y caracterizaron varios tipos de arcillas y las aguas de tres efluentes residuales industriales. Los componentes mayoritarios de las arcillas fueron: sepiolita: montmorillonita (76%); bentonita magnésica: vermiculita (74,4%); bentonita alumínica: esmectita (69,1%) y paligorskita (80%). Las aguas residuales se hicieron circular a través de lechos de cada una de las arcillas; manteniendo un tiempo de contacto de tres horas. Se analizó el contenido de metales pesados disueltos en las aguas antes y después de pasar a través de cada lecho. La sepiolita y la bentonita magnésica son eficaces para reducir la concentración de metales pesados en aguas residuales industriales. Se concluye que la adsorción depende del pH, del contenido de metales y del contenido de sólidos en suspensión en las aguas The effectiveness of the use of special clays for heavy metal removal from wastewater was evaluated. Various types of clays were tested on wastewater from three industrial effluents. The main components of the clays were sepiolite: montmorillonite (76%); magnesic bentonite: vermiculite (74,4%), aluminic bentonite: smectite (69.1 %) and palygorskite (80%). The wastewater was circulated through beds of each of the clays, maintaining a contact time of three hours. The heavy metal content in solution was analyzed before and after the water had circulated through the clay beds. The sepiolite and the magnesic bentonite were effective in reducing the heavy metal concentration of the industrial wastewater samples. The adsorption depended on pH and the metal content of the water, as well as its content of suspended solids

Published
2005

35. Time of flight secondary ion mass spectrometry and high-resolution transmission electron microscopy/energy dispersive spectroscopy: A preliminary study of the distribution of Cu2+ and Cu2+/Pb2+ on a Bt horizon surfaces

Author

Cerqueira, B., Vega, F.A., Serra, C., Silva, L.F.O., and Andrade, M.L.

Subjects
*TIME-of-flight mass spectrometry, *TRANSMISSION electron microscopy, *X-ray spectroscopy, *COPPER, *LEAD, *SOIL pollution, *SOIL absorption & adsorption, *HEAVY metals, *SOIL composition, *QUANTITATIVE research
Abstract

Abstract: Relatively new techniques can help in determining the occurrence of mineral species and the distribution of contaminants on soil surfaces such as natural minerals and organic matter. The Bt horizon from an Endoleptic Luvisol was chosen because of its well-known sorption capability. The samples were contaminated with Cu2+ and/or Pb2+ and both sorption and desorption experiments were performed. The preferential distribution of the contaminant species (63Cu and 208Pb) to the main soil components and their associations were studied together with the effectiveness of the surface sorption and desorption processes. The results obtained were compared with non-contaminated samples as well as with previous results obtained by different analytical techniques and advanced statistical analysis. Pb2+ competes favorably for the sorption sites in this soil, mainly in oxides and the clay fraction. Cu2+ and Pb2+ were mainly associated with hematite, gibbsite, vermiculite and chlorite. This study will serve as a basis for further scientific research on the soil retention of heavy metals. New techniques such as spectroscopic imaging and transmission electron microscopy make it possible to check which soil components retain heavy metals, thereby contributing to propose effective measures for the remediation of contaminated soil. [Copyright &y& Elsevier]

Published
2011
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36. Stability of some phenolic antioxidants in fatty preparations

Author

Irache, J.M., Diaz-Garcia, J.M., and Vega, F.A.

Abstract

Stability of butylated hydroxyanisole (BHA), propyl gallate (PG), trihydroxy butytophenone (THBP), tert-butyl hydroquinone (TBHQ) and a mixture of PG and BHA (1:1) in fatty preparations stored under three different conditions was studied. Each antioxidant was added to a fatty model to determine its degradation kinetics and its evolution during the oxidation of the fatty product. Their degradation was adequately described by a first-order kinetic process. An opposite relationship between the stability of antioxidants and their rate protection against oxidation of the fatty product was obtained. At 25°C, t90values ranged between 10 days for TBHQ and 61 days for BHA. On the other hand, compared when they were formulated alone, the increase of PG and the diminution of BHA degradation kinetics were observed. A degradation product arising from TBHQ was found in samples and stock solutions; an HPLC method for its identification is proposed with detection at 254 nm.

Published
1993
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