Separation of linear hydrocarbons and carboxylic acids from ethanol and hexane solutions by reverse osmosis |
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| Institution: | 1. National Institute of Materials and Chemical Research, Tsukuba, Japan;2. Institute of Industrial Science, University of Tokyo, Tokyo, Japan;1. State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, PR China;2. Collaborative Innovation Center of Chemical Science and Chemical Engineering, Tianjin 300072, PR China;3. Tianjin Ringpu Bio-Technology CO., LTD, Tianjin 300072, PR China;1. Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China;2. University of Chinese Academy of Sciences, Beijing 100039, China;3. Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), China;1. Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA;2. Materials Science & Engineering Division, National Institute of Standards and Technology, MS 8542, 100 Bureau Drive, Gaithersburg, MD 20899, USA;1. Chemical Process Engineering – AVT.CVT, RWTH Aachen University, Turmstrasse 46, 52064 Aachen, Germany;2. DWI-Leibniz-Institute for Interactive Materials, Forckenbeckstraße 50, 52074 Aachen, Germany |
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| Abstract: | In this study, asymmetric cellulose acetate membranes with moderate NaCl rejection (85.5%) were prepared and used to study the influence of the chemical nature of organic solutes in different organic solvents. The solute rejection and the solvent flux of linear hydrocarbons (Mw=226–563 g/mol) and linear carboxylic acids (Mw=228–340 g/mol) in ethanol and hexane were studied as a function of the molecular weight, the feed concentration and the transmembrane pressure.The ethanol flux was three times higher than the hexane flux. The rejection coefficients for both types of solute were quire acceptable (R=60–90%), when ethanol was the solvent. In hexane the linear hydrocarbons showed a rejection of 40–60%, while all carboxylic acids reached a negative rejection of ?40 to ?20%. This negative “observed” rejection can be attributed to accumulation of carboxylic acid at the membrane; the solute concentration at the membrane becomes much higher than in the bulk solution, due to a higher affinity of the solute with the membrane in hexane than in ethanol. Sorption experiments support this hypothesis.Furthermore, it was found that the rejection increases with increasing molecular weight and the rejection and flux are hardly affected by the feed concentration. |
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