View metadata,Downloaded citation and from similar orbit.dtu.dk papers on:at core.ac.uk Dec 18, 2017 brought to you by CORE provided by Online Research Database In Technology Thermodynamic Modelling of Surfactant Solutions Cheng, Hongyuan; Stenby, Erling Halfdan; Kontogeorgis, Georgios Publication date: 2004 Document Version Publisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Cheng, H., Stenby, E. H., & Kontogeorgis, G. (2004). Thermodynamic Modelling of Surfactant Solutions. 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Increasing energy efficiency and the reduction and/or prevention of the emission Thermodynamic Modelling of Surfactant Solutions of environmentally harmful substances are principal areas of focus when striving to attain a sustainable development. These are the key issues of the CHEC (Combustion and Harmful Emission Control) Hongyuan Cheng Research Centre at the Department of Chemical Engineering of the Technical University of Denmark. CHEC carries out research in 2003 fields related to chemical reaction engineering and combustion, with a focus on high-temperature processes, the formation and control of harmful emissions, and particle technology. In CHEC, fundamental and applied research, education and know- Ph.D. Thesis ledge transfer are closely linked, providing good conditions for the application of research results. In addition, the close collabora- tion with industry and authorities ensures that the research activ- ities address important issues for society and industry. CHEC was started in 1987 with a primary objective: linking funda- mental research, education and industrial application in an inter- nationally orientated research centre. Its research activities are technical university of denmark funded by national and international organizations, e.g. the Tech- department of chemical engineering nical University of Denmark. ISBN: 87-91435-00-5 Thermodynamic Modelling of Surfactant Solutions Hongyuan Cheng 2003 Department of Chemical Engineering Technical University of Denmark DK-2800 Kongens Lyngby, Denmark Copyright © Hongyuan Cheng, 2004, ISBN 87-91435-00-5 Printed by BookPartnerMedia, Copenhagen, Denmark Preface i Preface This thesis is submitted as a partial fulfilment of the Ph.D. degree at the Technical University of Demark. The project, granted by the Danish Environmental Research Programme, has been carried out from January 2000 to June 2003 at the Department of Chemical Engineering, Technical University of Denmark under the supervision of Professor Erling Stenby and associate Professor Georgios Kontogeorgis. I wish to thank my supervisors for their guidance, their ideas, and their ability to encourage me. My thanks also extend to Professors Peter Rasmussen, Jørgen Mollerup, Michael Michelsen, Simon Andersen and Kaj Thomsen in IVC-SEP for discussions on the new research topic. I would also like to thank Dr. Chau-Chyun Chen for our many discussions on matters of modelling surfactant solutions through email and during his visit in Denmark. My thanks also give to my family, my wife Hongwen Li and my son Fan Cheng for their support and understanding during the past years. Finally, I wish to thank all members of the IVC-SEP for making the past years so successful. Hongyuan Cheng Kongens Lyngby, October 2003 Preface ii Summary iii Summary In this work, the key physical properties of non-ionic and ionic surfactant solutions, such as the critical micelle concentration (CMC) and the octanol-water partition coefficient (Kow), are studied by molecular thermodynamic methods based on UNIFAC. The mean activity coefficients of the aqueous electrolyte and organic electrolyte solutions are modelled by a modified Achard’s UNIFAC model proposed in this work. Some of important properties in the surfactant solutions, such as the hydrophilic-lipophilic balance (HLB), the Krafft point (KP), the cloud point (CP), the aggregation number (ng), the toxicity (EC50) and the bio- concentration factor (BCF) are also investigated. And suitable correlations have been developed. Surfactant solutions are unique systems because the surfactant molecules form micelles in aqueous and non-aqueous solvents by self-assembly under the hydrophobic interaction with solvent molecules. Surfactant solutions have attracted much attention from academia and industry because they play important role in different industrial areas, e.g. chemical and oil industry, pharmaceutical and bio-industries, paper, food and film industries. In this work, different thermodynamic frameworks for the micelle formation of surfactant molecules in aqueous solution are systematically reviewed and compared. The method proposed by Chen et al. (Chen, C.-C., AIChE J., 42, 3231, 1996; Chen, C.-C., C. P. Bokis, and P. Mathias, AIChE J., 47, 2593, 2001) is selected for studying the micelle formation of surfactant molecules in aqueous solutions. Based on the method of Chen (1996), the CMC of non-ionic surfactant solutions is correlated and predicted successfully with the UNIFAC method. In this step, a new UNIFAC functional group is introduced. The necessary interaction parameters for the new group are obtained from vapour-liquid equilibrium data. In order to correlate the CMC of ionic surfactant solutions, an electrolyte UNIFAC model proposed by Achard et al. (Achard C., C. G. Dussap, and J. B. Gros, AIChE J., 40, 1210 , 1994a; Achard C., C. G. Dussap, and J. B. Gros, Fluid Phase Equilibria, 98, 71, 1994b) is modified and used to correlate the mean ionic activity coefficient of aqueous electrolyte and organic electrolyte solutions. It was found that the structural parameters (Q, Summary iv R) of ions used in the work of Achard and others do not follow Flory-Huggins assumption (Q/Rd1). Thus, a new method is developed to calculate the Q, R of ions from ionic radii using the condition Q/R<1. The mean activity coefficients of some aqueous electrolyte solutions are correlated with the modified Achard method and compared with the electrolyte NRTL and the extended UNIQUAC models. The mean activity coefficients of five sodium carboxylate systems are correlated simultaneously with the modified Achard model. The correlation results show a good agreement with the experimental values. Based on the work of Chen et al. (2001), the CMC of sodium alkyl sulphates, sodium alkyl sulfonates and potassium carboxylates are successfully correlated using the modified Achard model. Furthermore, the Kow of phthalates and non-ionic surfactants are predicted with different UNIFAC methods and commercial software. The prediction results are compared with the few experimental data available. Finally, some correlations for properties of surfactant solutions, i.e. HLB, KP, CP, ng, EC50 and BCF are presented. Summary v Summary in Danish – Resume på dansk I Ph.D arbejdet er de vigtige fysiske egenskaber af ikke-ioniske og ioniske surfaktantopløsninger, så som kritisk micelle koncentration (CMC) og oktanol-vand fordelingskoefficient (Kow), undersøgt ved molekylære termodynamiske metoder baseret på UNIFAC. Middel-ion-aktivitetskoefficienter for vandige elektrolytopløsninger og organiske elektrolytopløsninger er modelleret vha. en modificeret Achard’s UNIFAC model foreslået i denne afhandling. Nogle vigtige egenskaber for surfaktantopløsninger, som hydrofil-lipofil balance (HLB), Krafft punkt (KP), ”cloud”-punkt (CP), aggregationstal (ng), toksisitet (EC50) og bio-koncentrationsfaktor (BCF) er ligeledes bestemt og passende korrelationer er udviklet. Surfaktantopløsninger er unikke systemer, fordi surfaktantmolekyler i vandige og ikke- vandige opløsningsmidler danner miceller ved selvorganisening ved hydrofob vekselvirkning med solventmolekyler. Surfaktantopløsninger har fået megen akademisk og industriel opmærksomhed, fordi de spiller en vigtig rolle på forskellige industrielle områder, f.eks. olie- og kemisk-industri, farmaceutisk- og bio-industri, papir, fødevare og film industri. I Ph.D. arbejdet, er forskellige termodynamiske metoder for micelledannelse af surfaktantmolekyler i vandig opløsning systematisk undersøgt og sammenlignet. Metoden foreslået af Chen et al. (Chen, C.-C., AIChE J., 42, 3231, 1996; Chen, C.-C., C. P. Bokis, and P. Mathias, AIChE J., 47, 2593, 2001) er udvalgt for yderligere at undersøge micelledannelse af surfaktantmolekyler i vandige opløsninger. Baseret på Chens metode (1996), er CMC af ikke-ioniske sufaktantopløsninger korreleret og forudsagt med succes ved anvendelse af UNIFAC metoden. I dette trin er en ny funktionel gruppe introduceret