Magnetic-lignin Nanoparticles as Potential Ethanol Extractants from Aqueous Solutions

Date of Award

2019

Degree Name

M.S. in Chemical Engineering

Department

Department of Chemical and Materials Engineering

Advisor/Chair

Advisor: Erick Vasquez

Abstract

Ethanol extraction from aqueous solutions, such as biofuel fermentation broths, is a highly energy-intensive process with high operational costs. Currently, unit operations such as distillation, dehydration by vacuum distillation, and extractive distillation are used to obtain ethanol at a high purity level from aqueous streams, which is challenging due to the azeotrope formation. Alternative technologies using ionic liquids in liquid-liquid extraction have been proposed for ethanol extraction processes; however, these liquids are not environmentally friendly, have high toxicity, and possess complex structures. Hence, the utilization of other solvents in liquid-liquid extraction could become a more attractive process for ethanol extraction from aqueous solutions. Vegetable oils, fatty esters, hydrocarbons, and fatty alcohols have been proposed as green solvents and as the extract phase based on separation factors and distribution coefficients and due to their inherent low-cost. For instance, as compared to many other green solvents, a high distribution coefficient for castor oil in ethanol extraction from water has been found, suggesting a high capacity of this solvent in ethanol separation processes. Nonetheless, few studies focus on understanding the fundamental principles of extraction and phase equilibria for extract solvents. In this study, a liquid-liquid equilibrium study of the ternary system comprised of castor oil, water, and ethanol is obtained experimentally for the first time using a gas chromatograph system equipped with a headspace autosampler. In addition to obtaining the ternary diagram for castor oil/water/ethanol mixtures, this study analyzes the use of bio-based lignin magnetic nanoparticles to increase the extract phase ethanol separation efficiency. Lignin is an underutilized renewable resource that has high adsorptive properties, which combined with magnetic nanoparticles, could aid significantly in many liquid-liquid extraction processes due to its inherent aromatic characteristics. To optimize the preparation of the lignin magnetic nanomaterials, multiple mass ratios of lignin to magnetite were used in the synthetic steps followed by a complete characterization analysis using a variety of experimental techniques including spectroscopy, microscopy, and magnetization measurements. Fundamental studies on surface tension, interfacial tension, and ethanol adsorption are presented and discussed to understand the effects of lignin magnetic hybrid nanomaterialsin the ethanol/water/castor-oil ternary system. Overall, this work shows the potential of lignin magnetic nanoparticles as ethanol adsorbents that could ultimately aid a liquid-liquid extraction process that utilizes a green solvent such as castor oil in ethanol extraction from aqueous solutions.

Keywords

Chemical Engineering, Materials Science, Chemistry, Nanoscience, Sustainability, Ethanol extraction, magnetic nanoparticles, ternary diagram, castor oil, lignin-magnetite

Rights Statement

Copyright © 2019, author

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