Aquest treball contribueix a l'estudi de la sorció de metalls preciosos en chitosan, presentant-lo com una futura alternativa a nivell industrial en front dels altres processos ja utilitzats actualment. Concretament el nostre estudi esta centrat en la recuperació de metalls preciosos provenint de solucions clorhídriques a baixes concentracions.

Degut a l'alt valor i poca abundància d'aquests metalls, es necessari desenvolupar i consolidar nous processos de recuperació i separació per aquests metalls.

El treball presentat en aquesta tesi ha estat planificat basant-se en la contribució entre l'estudi de les propietats del chitosan realitzada en el "Laboratoire Gènie de l'Environnement Industrial de l?Ecole des Mines d?Alès" i per la investigació del comportament dels metalls preciosos en solució realitzada en el Departament de Enginyeria Química de la Universitat Politècnica de Catalunya.

Per portar els nostres objectius a terme, el primer treball va consistir en el estudi de les condicions d'equilibri i en les cinètiques d'adsorció del pal·ladi utilitzant flocs de chitosan. Aquest estudi es va realitzar en reactor tancat i obert.

Un cop aquesta part del treball va ser realitzada el nostre interès es va centrar en l'obtenció de nous derivats del chitosan que milloressin la seva capacitat d'adsorció, insertant derivats de sofre a la cadena de chitosan. Aquests nous derivats van ser utilitzats per l'estudi de la capacitat de sorció del platí i pal·ladi.

Per altre part degut als problemes generats per el alt contingut d'aigua en les perles de chitosan fabricades, es va realitzar un estudi amb perles prèviament secades i posteriorment rehidratades.

Finalment les nostres investigacions per tal de completar el nostre treball es van ampliar per l'estudi del osmi, iridi, rodi, ruteni.

Aquesta Tesi Doctoral resumeix el treball presentat en els següents articles:

I. Palladium Sorption on Glutaradehyde Crosslinked ChitosanM. Ruiz, A. M. Sastre i E. GuibalReactive & Functional Polymers, 45, 155-173 (2000)
II. Palladium Sorption on Glutaraldehyde-Crosslinked Chitosan in Fixed-Bed SystemsM. Ruiz, A. M. Sastre, M. C. Zikan i E. GuibalJournal of Applied Polymer Science, 81, 153-165 (2001)
III. Platinum and Palladium Sorption on Chitosan DerivativesE. Guibal, M. Ruiz, T. Vincent, A. M. Sastre i R. Navarro MendozaSeparation Science and Technology, 36 (5 & 6), 1017-1040 (2001)
IV. Palladium Sorption Using Chitosan DerivativesM. Ruiz, A. M. Sastre, J. R. Degorce-Dumas i E. GuibalTexts of textes des affiche posters. International Water Association (2000). ISBN: 2-9515416-0-0
V. Pd and Pt Recovery Using Chitosan Gel Beads. I. Influence of Drying Process on Diffusion PropertiesM. Ruiz, A. M. Sastre, E. GuibalSeparation Science and Technology (2002), en premsa
VI. Pd and Pt Recovery Using Chitosan Gel Beads. II. Influence of Chemical Modification on Sorption PropertiesM. Ruiz, A. M. Sastre, E. GuibalSeparation Science and Technology (2002), en premsa
VII. Influence of Drying Process of Chitosan Beads on the Sorption of Platinum and PalladiumM. Ruiz. A. M. Sastre i E. GuibalAdvances in Chitin Sciences, VI, (2002), en premsa
VIII. Osmium and Iridium Sorption on Glutaraldehyde Crosslinked Chitosan Gel BeadsM. Ruiz, A. M. Sastre i E. GuibalSolvent Extraction Ion Exchange, sotmès per a publicació

This work contributes to the study of the sorption of precious metals on chitosan, presenting it as a future alternative at an industrial level to the various existing processes.

This study is focused on the recovery of precious metals from hydrochloric acid solutions by techniques based in sorption on natural polymers.

Due to the high value and scarcity of precious metals, the need of developing and consolidating new separation and concentration processes is very important.

The work presented in this thesis has been planified and based on the contribution given by the research of the properties of chitosan in the sorption of metals, realized in the "Laboratoire Gènie de l'Environnement Industrial de l'Ecole des Mines d'Alès" and by the research of the behaviour of the precious metals in solution, realized in the Department of Chemical Engineering, Universitat Politècnica de Catalunya.
To get this investigation under way and to be able to develop it, the first work consisted of the study of the equilibrium conditions and the adsorption kinetics of Pd in chitosan in the form or flakes. This study was carried out using a closed and open reactor system.

Once this part of the work had been carried out, the specific interest of this investigation focused on obtaining chitosan derivatives that might improve the sorption capacity for Pd and Pt, by grafting sulphur compounds onto the chitosan, and also including desorption studies for Pd.

Owing to the possible transport problems which the high water content of the pearls of chitosan might cause, a drying process was used, comparing the results with those previously obtained (paper V). At the same time the sorption capacity of Pd and Pt was improved, introducing more amino groups in the chitosan chains

Finally, owing to the fact that the main part of the work was dedicated to the sorption of Pd and Pt, it was decided to complete this study by extending it to the metals Rh, Ru, Os, Ir and Re.

The results obtained are shown in the following papers:

I. Palladium Sorption on Glutaradehyde Crosslinked ChitosanN. Ruiz, A. M. Sastre i E. GuibalReactive & Functional Polymers, 45, 155-173 (2000)
II. Palladium Sorption on Glutaraldehyde-Crosslinked Chitosan in Fixed-Bed SystemsN. Ruiz, A. M. Sastre, M. C. Zikan i E. GuibalJournal of Applied Polymer Science, 81, 153-165 (2001)
III. Platinum and Palladium Sorption on Chitosan DerivativesF. Guibal, M. Ruiz, T. Vincent, A. M. Sastre i R. Navarro MendozaSeparation Science and Technology, 36 (5 & 6), 1017-1040 (2001)
IV. Palladium Sorption Using Chitosan DerivativesN. Ruiz, A. M. Sastre, J. R. Degorce-Dumas i E. GuibalTexts of textes des affiche posters. International Water Association (2000). ISBN: 2-9515416-0-0
V. Pd and Pt Recovery Using Chitosan Gel Beads. I. Influence of Drying Process on Diffusion PropertiesN. Ruiz, A. M. Sastre, E. GuibalSeparation Science and Technology (2002), en premsa
VI. Pd and Pt Recovery Using Chitosan Gel Beads. II. Influence of Chemical Modification on Sorption PropertiesN. Ruiz, A. M. Sastre, E. GuibalSeparation Science and Technology (2002), en premsa
VII. Influence of Drying Process of Chitosan Beads on the Sorption of Platinum and PalladiumN. Ruiz. A. M. Sastre i E. GuibalAdvances in Chitin Sciences, VI, (2002), en premsa
VIII. Osmium and Iridium Sorption on Glutaraldehyde Crosslinked Chitosan Gel BeadsN. Ruiz, A. M. Sastre i E. GuibalSolvent Extraction Ion Exchange, sotmès per a publicació