Naslov
The influence of citrate and fluoride ions on dissolution kinetics of aluminium rotating disc electrode

Autori
Hasenay, Damir ; Šeruga, Marijan ; Jakobek, Lidija ; Medvidović, Martina

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Knjiga sažetaka XIX. hrvatskog skupa kemičara i kemijskih inženjera / Škare, Danko - Zagreb : Hrvatsko društvo kemijskih inženjera i tehnologa (HDKI) ; Hrvatsko kemijsko drustvo, 2005

Skup
XIX. hrvatski skup kemičara i kemijskih inženjera

Mjesto i datum
Opatija, Hrvatska, 24.04.2005. - 27.04.2005

Vrsta sudjelovanja
Poster

Vrsta recenzije
Domaća recenzija

Ključne riječi
aluminium; dissolution kinetics; citrate; fluoride

Sažetak
The influence of citrate and fluoride ions, particularly the influence of concentration and pH value of solutions containing citrate and fluoride ions, on dissolution kinetics of aluminium was studied. Measurements were performed by the means of controlled potential coulometry, using an EG&G PAR Model 273A Potentiostat and EG&G PAR Model 636 Rotating disc electrode system, remotely controlled by PC. Aluminium oxide surface which is spontaneously formed on Al-electrode in aqueous solution of citric acid is significantly hydrated. The hydration of aluminium-oxygene bonds and subsequent dissociation of the surface hydroxyl groups lead to the possibility of different surface reactions, such as adsorption and surface complexation. Adsorption of electrolyte anions from the solution containing citrate and fluoride ions is competitive and reversible. In citric acid solutions pH = 3...6 dissolution of aluminium is essentially controlled by the surface processes, i.e. the dissolution rate depends on the degree of surface protonation and on the concentration of surface complexes. Addition of fluoride ions in citric acid solutions pH = 3...6 increase dramatically dissolution rate of aluminium and change dissolution kinetics, from surface-controlled to mixed (both transport- and surface-) controlled. Observation of these effects can be very useful for electrochemical investigations of adsorption processes on aluminium rotating disc electrode [1, 2]. More specifically, by recording the dissolution current as a function of rotation rate it is possible to distinguish between transport-controlled and surface-controlled processes, and to characterize the elementary reactions and their sequence. Electrochemical measurements were performed for different flouride (5x10-4...5x10-5 mol dm-3) and citrate (10-6...10-1 mol dm-3) concentration in the pH region of 3...6. In addition, the influence of anodic potential of Al-electrode was also studied. It was found that the results can be well described by the Langmuir adsorption isotherm from which it is possible to calculate the adsorption equilibrium constant for citrate adsorption on Al-electrode surface.

Izvorni jezik
Engleski

Znanstvena područja
Prehrambena tehnologija

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