(188e) Cellulose Nanocrystals- and Lignin Magnetic Nanocomposites Enhance the Ethanol Extraction from Aqueous Solution Using Castor Oil As the Extractant

Ethanol use as a gasoline additive keeps rising in the USA, with approximately 15,000 million gallons consumed in 2019. Multiple separation processes are needed to achieve low-water content ethanol, and commonly distillation is performed, which requires multiple stages and high energy consumption. This work focuses on using liquid-liquid extraction at room temperature to separate ethanol from its aqueous solution using castor oil as the extractant phase. We chose castor oil due to its high ethanol solubility, immiscibility with water, low toxicity, low cost, high boiling point (~ 313 °C), and low heat capacity. Also, we investigated superparamagnetic iron oxide, Fe₃O₄, nanoparticles coated with kraft lignin or Fe₃O₄-coated cellulose nanocrystals, and used these as additives to investigate the potential enhancement of the ethanol extraction process by imposing external magnetic fields. Kraft lignin, a hydrophobic material with low molecular weight, high stability, and high strength material, was chosen to protect the Fe₃O₄ nanoparticles from oxidation and formed multicore magnetic structures. Similarly, cellulose nanocrystals (CNCs) provided a hydrophilic substrate with a unique aspect ratio that served as a platform capable of attaching multiple magnetic nanoparticles onto its surface. The Fe₃O₄ nanoparticles and the biobased nanocomposites were synthesized and coated using the co-precipitation method and characterized using Fourier Transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, dynamic light scattering and zeta potential measurements, and vibrating sample magnetometry. For the liquid-liquid extraction experiments, different concentrations of ethanol aqueous solution (2%, 5%, 10%, 20%, and 30% wt.%) extracted by different ratios of castor oil (50%, 70% of total volume) were studied. Different amounts of nanoparticles (0, 0.15, 0.25, and 0.5 w/v%) added into the extraction system were studied. Ethanol aqueous solution and castor oil mixtures with nanoparticles were emulsified at 13,000 rpm for 5 minutes and kept at room temperature for 24 hours to reach equilibrium. A magnetic field (300 mT) was applied using a Neodymium rare-earth magnet to break-up the emulsions faster and separate the aqueous and the organic phase. After achieving phase separation, headspace gas chromatography (HS-GC-FID) was used to determine each phase's ethanol concentration. The liquid-liquid extraction experiments results showed that water/castor oil/ethanol emulsions were formed by adding modified-magnetic nanoparticles (lignin or CNCs). Due to the magnetic nanoparticles' presence, the emulsions were easier to separate into two phases under an external magnetic field. Our current studies revealed that the nanoparticles enhanced the extraction process by increasing the amount of ethanol transferred from the aqueous phase to the oil phase (50:50 v/v) by 33% compared to the liquid-liquid extraction, without the nanoparticles. Once ethanol transfers to the oil phase, and due to the boiling point difference between the castor oil and the ethanol, simple evaporation could lead to high ethanol purity levels.