Rheological properties characterization and flow behavior of water-jojoba biodiesel emulsions

This study investigates the flow behavior and rheological properties of stable water-in-jojoba biodiesel (WJBD) emulsions with varying water concentrations, aiming to enrich the endeavors of using WJBD emulsions as an alternative sustainable biofuel for diesel engines and exhaust emission reducer, as they were not addressed and published before. Jojoba biodiesel was synthesized through a transesterification process involving jojoba oil extract and methanol, catalyzed by sodium hydroxide. Rheological measurements, including shear stress, viscosity, and viscoelastic properties, were conducted using a MCR 92 rotational rheometer over a temperature range of 10–60 °C. Rotational and oscillating tests were conducted according to the required parameters to be measured to study the flow behavior and viscoelastic profile of WJBD emulsions with the impact of water concentration. Olympus IX83 Microscope has been utilized to record and examine the distribution of the water droplets phase within the jojoba biofuel emulsion. As for the emulsions, they were prepared with distilled water and a nonionic surfactant of Tween-80 using a high-speed homogenizer, creating mixtures with water ranging from 5 % to 15 % by volume in 5 % increments. The results indicate that the emulsions exhibit almost Newtonian behavior, with viscosity nearly constant as shear rate increases. Temperature effects on the shear stress and viscosity were found to mimic the behavior of conventional diesel fuel. Additionally, amplitude and frequency sweep tests were conducted to determine the storage and loss moduli, which provide insights into the emulsions’ elastic and viscous behavior, respectively. The results reveal that the storage modulus exceeds the loss modulus, indicating a predominantly elastic behavior up to a transition point, beyond which the behavior becomes more viscous. These findings highlight the potential of WJBD emulsions as a viable alternative fuel with properties that resemble those of conventional diesel, providing insights into their use in various industrial applications. The study advances the understanding of water-in-jojoba biodiesel emulsions by elucidating their flow and viscoelastic characteristics, thus providing a foundation for future research and development in this area.