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Browsing by Author "Reis, Ana T."

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  • Simultaneous removal of trace elements from contaminated waters by living Ulva lactuca
    Publication . Henriques, Bruno; Teixeira, Ana; Figueira, Paula; Reis, Ana T.; Almeida, Joana; Vale, Carlos; Pereira, Eduarda
    This work shows the capabilities of living seaweed, Ulva lactuca, to remove As, Cd, Pb, Cu, Cr, Hg, Mn and Ni from contaminated waters. Experiments were performed with three algal doses (1.5, 3.0 and 6.0 g L-1, FW), two ionic strengths (salinity 15 and 35), and trace element concentrations corresponding to the maximum allowed values in wastewaters. The highest removals were obtained with the algal dose of 6 g L-1, with efficiencies varying between 48% for As and 98% for Hg, after 24 to 72 h. Salinity showed no effect on the removal efficiency. Overall, Elovich model was the best in describing the kinetics of the process, except for Hg, where pseudo-second-order model performed better. The use of extractions with EDTA (0.001, 0.01 to 0.1 mol L-1) has clarified that most of the Hg (≈98%) and Cr (≈80%) crossed the macroalgae walls, while Ni, Cd and As were retained at the surface (between 60 and 80%). These results support the hypothesis that macroalgae-based technologies may be a viable, cost-effective, and greener option to reduce the rejection of priority hazardous substances in contaminated waters.
    2018-10-22Journal article Restricted access Show more
  • A Single Digestion Procedure for Determination of Major, Trace, and Rare Earth Elements in Sediments
    Publication . Carvalho, Lina; Reis, Ana T.; Soares, Eugénio; Tavares, César; Monteiro, Rui J.R.; Figueira, Paula; Henriques, Bruno; Vale, Carlos; Pereira, Eduarda
    The simultaneous determination of major, trace, and rare earth elements in sediments requires the development of specific procedures to prevent interfer- ences. A single digestion method adapted from the EPA method 3051A is proposed for the quantification of 42 elements in sediments by inductively coupled plasma techniques associated with optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP- MS). A combination of different acids and microwave- assisted acid extraction following hot plate extraction was tested. Evaluation of applicability range, linearity, limits of detection and quantification, selectivity, repeat- ability, intermediate precision, and trueness showed the accurate determination of all elements. Selectivity, pre- cision, and trueness values were below the criteria established by the laboratory. The applicability of the proposed method was tested in real sediment samples. For each element, difference between duplicates was lower than the corresponding repeatability limit, with the coefficients of variation ranging between 1.7 and 14%. These results point to the usefulness of this meth- od in multi-element determination of major, minor, trace, and REE in sediment samples, showing its appli- cability in environmental studies related, namely to sediment characterization, monitoring programs, assess- ment of environmental impacts, sediment provenance, and post-depositional mechanisms.
    2020-10-27Journal article Restricted access Show more