XII Iberian Meeting of Electrochemistry XVI Meeting of the ...

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XII Iberian Meeting of Electrochemistry & XVI Meeting of the Portuguese Electrochemical Society PA 01 Nickel Speciation in the Xylem Sap of the Hyperaccumulator Alyssum serpyllifolium ssp. lusitanicum G rowing on Serpentine Soils of Northeast Portugal Sheila Alves 1 , Cristina Nabais 2 , Maria de Lurdes Simões Gonçalves 1 , Margarida M. Correia dos Santos 1 1 Centro de Química Estrutural, IST, Av. Rovisco Pais, 1049-001, Lisboa, Portugal. 2 Centro de Ecologia Funcional, FCT, Universidade de Coimbra, 3000 Coimbra, Portugal sheila@ist.utl.pt Due to the dynamic nature of voltammetric methods, it is possible to have knowledge on the kinetics of the interconversion of the species present in solution and also to obtain information regarding the concentration of those species [1]. As previously reported, Square Wave (SW) and Cyclic Voltammetry proved to be efficient tools in a speciation study of Ni in the xylem sap of Quercus ilex, vulgar holly oak [2,3]. In this work SW Voltammetry was used to provide a model for Ni speciation in the xylem sap of Alyssum serpyllifolium Desf. ssp. lusitanicum Dudley & Silva, a Nihyperaccumulator endemic to the serpentine soils of northeast Portugal. The xylem sap was collected from plants growing in its native habitat and characterized in terms of Ni, Ca and Mg content using Flame atomic Absorption Spectrometry [4] and carboxylic and amino acids content using Reverse Phase High Performance Liquid Chromatography with Diode Array Detection (RP-HPLC-DAD) [5]. Thereafter Ni speciation was study in model and real solutions of xylem sap by SW voltammetric titrations at 0.10 M ionic strength and pH = 7.0 (figure 1). The results showed that Ni transport in the xylem sap occurs mostly as a free hydrated cation (about 70%). Citric acid is the main Ni complexing ligand (18% of total Ni). Oxalic, aspartic, malic and malonic acids complexes account for approximately 5, 4, 2 and 2% of total Ni, respectively. The coordination to other amino acids is negligible [5]. Acknowledgments: This work was co-financed by POCI 2010 and by the European Social Fund. Sheila 50 Alves acknowledges F CT for PhD Grant SFRH/BD/21597/2005. [Ni] Free 10 6 M Figure 1. SW voltammograms of the titration of A. serpyllifolium ssp. lusitanicum xylem sap diluted solution with nickel E / V vs. Ag/AgCl -1.5 -1.3 -1.1 -0.9 40 50 References [Ni] 0 [1] Mota A.M.; Correia dos Santos M.M. In: Metal Speciation 30 0 and 50 Bioavailability 100 150 in Aquatic [Ni] t, 10 6 M Systems (eds: Turner D.; Tessier A.), Wiley, 1995, pp. 205-258. [2] Correia dos Santos, M.M.; 20 Santos, M.M.; Alves, S.; Simões Gonçalves, M.L. Electroanalysis, 2007, 19, 2351. [4] Alves, S.; 10 Gonçalves, M.L.S.; Correia dos Santos, M.M. Phytochemical Analysis, 2009, 20, 365. [5] Alves, B [Ni] Free 10 6 M A Incre asin Alves, S.; Simões Gonçalves, M.L.; Nabais C. Electroanalysis, 2006, 18, 814. [3] Correia dos S.; Nabais C.; Gonçalves, M.L.S.; Correia dos Santos, M.M. Submitted for publication. 150 100 g 0 -20 -40 -60 -80 -100 -120 -140 0 0 10 20 30 40 50 [Ni] t , 10 6 M I / nA September, 811, 2010. ISEL - Lisbon 56
XII Iberian Meeting of Electrochemistry & XVI Meeting of the Portuguese Electrochemical Society PA 02 Electrodegradation of 4-aminonaphtalene-1-sulfonic acid with BDD and Ti/Pt/PbO 2 Anodes A.S. Rodrigues, M.J. Pacheco, L. Ciríaco, A. Lopes UMTP and Department of Chemistry, University of Beira Interior, 6201-001 Covilhã, Portugal asfrodrigues@hotmail.com Naphthalene sulfonic amines are very toxic pollutants released to the environment in the effluents of several industries, especially in the textile industry. Many of this type of pollutants are biorefractory and electrochemical processes, such as anodic oxidation using anodes with high oxygen overpotential, like boron doped diamond (BDD) and Ti/Pt/PbO 2 , have become an alternative method to achieve their degradation [1]. Both anodes have high oxidation power and are able to generate highly reactive physisorbed hydroxyl radicals. The aim of this work was to study the performance of the above mentioned anodes, BDD and Ti/Pt/PbO 2 , in the anodic oxidation of 4-aminonaphtalene-1-sulfonic acid, using as supporting electrolyte two different salts: NaCl and Na 2 SO 4 . Ti/Pt/PbO 2 electrodes, with geometric area of 10 cm 2 , were prepared by thermal electrochemical method [2]. The BDD electrode was purchased from Adamant Technologies/CSEM. The electrochemical assays were performed in galvanostatic mode, at 300 A m -2 imposed current density. The electrochemical assays were run in an electrochemical cell, with a BDD or Ti/Pt/PbO 2 anode, working in batch mode. Degradation of 4-aminonaphtalene-1-sulfonic acid was followed by UV-VIS spectrophotometry, Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) determinations. When the performance of both anode materials is compared, in the tests run with NaCl as electrolyte, it can be concluded that the mineralization is always higher for the BDD anode, since after 6 h assay TOC removal was 61% for this electrode and 21% for the Ti/Pt/PbO 2 . However, in what concerns COD removals, the difference between the BDD and 90% for those performed with Ti/Pt/PbO 2 . The analysis of data obtained with chlorides suggest that COD removal occurs in the first hours of electrolysis, while, with sulfates, removal occurs gradually throughout the test. In spite of this different behavior, the final COD removal, after 6 h, is only slightly dependent on the electrolyte. Acknowledgments: The financial support of Fundação para a Ciência e a Tecnologia, F CT, BII- 12/UMTP/UBI/2009. References [1] Ciríaco L.; Anjo C.; Correia J.; Pacheco M.J.; Lopes A. Electrochimica Acta, 2009, 54, 1464. [2] Andrade L.S.; Rutuolo L.A.M.; Rocha-Filho R.C.; Bocchi N.; Biaggio S.R.; Iniesta J.; Garcia- Garcia V.; Montiel V. Chemosphere, 2007, 66, 2035. September, 811, 2010. ISEL - Lisbon 57
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