Surface Modifications of Cellulose Nanocrystals: Applications in Stabilization and Demulsification of Magnetically Controlled Castor Oil/water/ethanol Pickering Emulsions for Liquid-liquid Extraction of Ethanol from Water
This doctoral dissertation focuses on surface modification of cellulose nanocrystals (CNC) by two modification techniques and application of the modified CNCs in magnetically controllable castor oil/water/ethanol Pickering emulsions for liquid-liquid extraction of ethanol from water. At first, a greener hydrophobic CNC was synthesized by oxa-Michael addition of N-Benzylmaleimide to the hydroxyl group of CNC surface following green chemistry principles. The modified CNCs were found to have higher thermal stability and increased hydrophobicity than the pristine CNC and they have applications in bio-composites, reinforced polymer nanocomposites, Pickering emulsions, and controlled drug delivery systems. The second modified CNC was obtained by coating the CNCs surface with Fe3O4 nanoparticles in one-step co-precipitation of iron chloride salts by ammonium hydroxide in the presence of CNC. As synthesized superparamagnetic CNC@Fe3O4 nanoparticles was studied in stabilizing castor oil/water/ethanol emulsions for the liquid-liquid extraction of ethanol from water using the castor oil as an extractant. Moreover, lignin-coated iron oxide nanoparticles (lignin@Fe3O4), obtained from the University of Dayton, was also tested in stabilizing the castor oil/water/ethanol emulsions. The effect of CNC@Fe3O4 and lignin@Fe3O4 nanoparticles in magnetically-controllable demulsification was also tested. The results demonstrated that both CNC@Fe3O4 and lignin@Fe3O4 nanoparticles successfully emulsified the castor oil/water/ethanol mixtures and magnetically demulsified the emulsions on demand. Furthermore, the ternary liquid-liquid equilibrium diagram of castor oil/water/ethanol mixtures was developed experimentally and the data were successfully correlated with UNIQUAC and NRTL model. The resulting high distribution coefficient and selectivity of ethanol suggested that castor oil was a good solvent for extracting ethanol.