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Adsorption-desorption kinetics of dicarboxylic acids on synthesized iron oxide nano- and mesoporous particles
2008 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The adsorption-desorption of aliphatic acid on mineral oxide surfaces regulates several environmentally significant chemical reactions. The kinetics of these reactions provides useful information on the evaluation and prediction of the adsoption rate and implies fundamental information on the adsorption mechanism. In the current work, nano and mesoporous iron oxide has been successfully synthesized using the ultrasonic method. The adsorption of dicarboxylic acid (succinic acid and maleic acid) at the hematite/water interface was studied by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The kinetics of adsorption was investigated at different initial bulk concentrations and various pH values. The results show that both adsorption and desorption of the two dicarboxylic acids studied are characterized by a fast initial reaction during the first 10 minutes and a much slower reaction eventually reaching a plateau value after several hours. The adsorption rate increases by increasing concentration and at pH 5 the adsorbed amount and the total rate of reaction rate is higher than at pH 3 and pH 8. This indicated that electrostatic interaction plays an important role in the adsorption process. Clear spectral differences between the two kinds of dicarboxylic acids upon adsorption onto hematite allowed us to discriminate between chemisorbed and physically adsorbed species as well as inner-sphere/outer-sphere complexes. It was shown that succinic acid is chemisorbed at the hematite surface, whilst the -CH=CH- alkenyl segment in the hydrocarbon chain of maleic acid seemed to prohibit its chemisorption on the surface. Furthermore, for succinic acid, both inner-sphere and outer-sphere complexation existed simultaneously at all pH values. The desorption experiments performed turned out to be very helpful in order to distinguish between inner-sphere and outer-sphere complexation. The initially adsorbed molecules contributing to the higher reaction rate is interacting with the hematite surface through hydrogen bonding interaction (outer-sphere complexation). Eventually, at a lower reaction rate, these outer sphere complexes are forming chemically bonded inner-sphere complexes.

Place, publisher, year, edition, pages
Keyword [en]
Physics Chemistry Maths, Iron oxide, Adsorption, Desorption, Kinetics, Mechanism
Keyword [sv]
Fysik, Kemi, Matematik
URN: urn:nbn:se:ltu:diva-55158ISRN: LTU-PB-EX--08/046--SELocal ID: c0ccbcac-42bc-496e-bcbb-e322e1cdd588OAI: diva2:1028539
Subject / course
Student thesis, at least 30 credits
Educational program
Chemical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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