Comunicaciones a congresos, Conferencias, … (Fac. de Ciencias)
Permanent URI for this collectionhttps://hdl.handle.net/10171/70279
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- Distinct complexing trends of chitosan with toxic metals (PO1-24)(European Chitin Society, 2009-05-23) Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)We have been able to prove that not only adsorption but also complexation of different metals (Pb, Cd, Mo, Cu, Zn and Cr) actually takes place in acetate buffer (pH=4) with Chitosans of different molecular weights and deacetylation degrees. Depending on the different electrochemical behaviour on mercury electrode of studied metals and the nature of the resulting complexes, diverse approaches have been used. Chitosan molecular weight and concentration had been seen to play a key role in the Chitosan binding activity with Zn, Pb and Cd, as reported elsewhere[1]. Length of Chitosan chains influences the degree of complexation with both Cr and Mo, while Cu binding capacity remains independent of the molecular weight of the assayed polymers. The larger the polymer chain length the higher the number of amino group available for the retention of both Cr and Mo within the tridimensional structure of the acting ligand. This is consistent with a predominant intra-chain linkage of both metal atoms. On the contrary, in the case of Cu, an inter-layer binding mechanism is proposed as the main retention factor by Chitosan.
- Biopolymer-cement composites for building purposes: performance of chitosan and some of its derivatives as cement admixtures(Mahatma Gandhi University, 2010-09-24) Alvarez-Galindo, J.I. (José Ignacio); Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)Invited lecture presented on the 2nd ICNP held in Kottayam, India on 24th September 2010.
- Chitosan-cement matrices for solidification-stabilization of heavy metals(University of Birmingham, 2010-09-13) Alvarez-Galindo, J.I. (José Ignacio); Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)Cement matrices have been extensively used to solidify-stabilize hazardous wastes containing heavy metals [1]. However, the presence of some heavy metals such as Pb and Zn modify the rheological properties of the cement due to the interaction with different cement phases [2], [3]. These changes in fresh-state properties of the cement materials may have a negative influence on the applicability of these matrices. Moreover, the hardened-state properties could be affected by the fresh-state changes and, consequently, the long-term stability and leaching of the heavy metals would be jeopardized. The use of some polymeric additives may be interesting in order to solve the aforementioned problems. Polysaccharides have been reported to be efficient cement additives behaving as viscosity-enhancing admixtures and set retarders [4].
- Voltammetric evaluation of chitosan as an effective complexing ligand for the removal of toxic heavy metals(ISE, 2008-09-07) Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)Program of the 59th Annual Meeting of the International Society of Electrochemistry, 2008:138: The aim of this study is to evaluate de complexation of toxic heavy metals such as Pb, Zn, Cd and Cu by three commercial chitosans with different molecular weights. For this purpose, the complexation capacity of chitosan was evaluated through competitive deposit of the metals onto the HMDE from ligand-containing solutions and subsequent voltammetric measurement of the anodic stripping signal. Chitosan and spiked metal solutions were dissolved in an acetic-acetate buffer solution (pH=3,5). The complexation capacity was also evaluated at different concentrations of chitosans. Up to now, preliminary results indicate that chitosan complexes more effectively Zn than Pb, probably due to the lower size of Zn which allows its inclusion into the available linking sites of chitosan. Besides, Zn stripping peak shows a marked decrease in its intensity and a displacement towards less negative potentials, proving the high affinity of chitosan for Zn.
- An etherified derivative of chitosan as an improved complexing agent for solidification/stabilisation of heavy metals into cementitious matrices(2010-06-20) Alvarez-Galindo, J.I. (José Ignacio); Bessard, B. (Benjamin); Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)Book of abstracts of the13th International Conference on Electroanalysis ESEAC, 2010; PIN50:357: Chitosan is a natural widely available biopolymer and increasingly used for most diverse applications. Different chitosans of various molecular weight and deacetylation degrees have been previously checked as for their complexing activity towards selected target heavy metals, such as Zn, Pb, Cd, Cu, Mo and Cr [1,2]. Some rheological properties of cementitious matrices have been seen to improve upon incorporation of those biopolymers, such as water retention, setting time and consistency (through the flow table test). In this paper we report the different complexing patterns found for Zn and Pb when a chitosan derivative is used. These results will be discussed by comparison with the behaviour of the aforementioned non-modified chitosans.
- Assessment of the effect of pH values on the complexing ability of two etherified derivatives of chitosan with a view to improving retention of heavy metals into cement mortars(2010-06-20) Alvarez-Galindo, J.I. (José Ignacio); Bessard, B. (Benjamin); Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)Book of abstracts of the13th International Conference on Electroanalysis ESEAC, 2010; PIN50:358: Removal of heavy metals from polluted aqueous systems (industrial and waste waters) may be accomplished by complexing and sequestering them into inert matrices. A suitable matrix can be cement mortars, owing to the fact that they have the capability of immobilise and stabilise the complexes, reducing heavy metal leaching. The complexing ligand has to be properly chosen so that it presents high affinity for the metal and a good performance of the formed complex in the largely alkaline medium of the cement mortar. Our research interest is focused on chitosans and its derivatives as a model ligand that fulfills both demands. The complexing ability of unmodified chitosans for several target heavy metals has been checked in acetated buffer (pH = 4) [1]. In this contribution we will take advantage of the fact that some etherified chitosans are soluble in alkaline pH mimicking the cement mortar conditions. Retention of Zn and Pn in alkaline media by the etherified chitosans will be related to the heavy metal concentrations found in the leaching coming from polymer modified mortars.