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Proposed Models for Subcritical Water Extraction of Essential Oils

Chinese Journal of Chemical Engineering 2009年第3期17卷 359-365页

作者： M.Khajenoori A.Haghighi Asl F.Hormozi Chemical Engineering Department Faculty of EngineeringSemnan University

Mechanisms that control the extraction rate of essential oil from Zataria multiflora Boiss. (Z. multiflora) with subcritical water (SW) were studied. The extraction curves at different solvent flow rates were used to deter-mine whether the extractions were limited primarily by the near equilibrium partitioning of the analyte between the matrix and solvent (i.e. partitioning thermodynamics) or by the rates of analyte desorption from the matrix (i.e. ki-netics). Four simple models have been applied to describe the extraction profiles obtained with SW: (1) a model based solely on the thermodynamic distribution coefficient KD, which assumes that analyte desorption from the ma-trix is rapid compared to elution; (2) one-site kinetic model, which assumes that the extraction rate is limited by the analyte desorption rate from the matrix, and is not limited by the thermodynamic (KD) partitioning that occurs dur-ing elution; (3) two-site kinetic model and (4) external mass transfer resistance model. For SW extraction, the thermodynamic elution of analytes from the matrix was the prevailing mechanism as evidenced by the fact that ex-traction rates increased proportionally with the SW flow rate. This was also confirmed by the fact that simple re-moval calculations based on determined KD (for major essential oil compounds) gave good fits to experimental data for flow rates from 1 to 4 ml·min-1. The results suggested that the overall extraction mechanism was influenced by solute partitioning equilibrium with external mass transfer through liquid film.

关键词： essential oils Zataria multiflora Boiss. subcrltlcal water extraction mechanisn

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INVESTIGATION ON SURFACE FEATURE OF NEODYMIUM YTTRIUM ALUMINIUM TETRABORATE CRYSTAL

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Chinese Science Bulletin 1991年第24期36卷 2088-2092页

作者：张吉果潘恒福陆宝生 Institute of Crystal Materials Shandong UniversityJinan 250100 PRC

Ⅰ. INTRODUCTION Neodymium yttrium aluminium tetraborate [NdxY1-xAL （BO3）4, （NYAB）] is a functional material which is self-activated and self-frequent doubling. It belongs to an incongruent compound in the phase d... 详细信息

关键词： NdxY1-xAL(BO3)4 crystal straight steps and mat-like striation growth hillocks growth spirals crystal growth mechanisn

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