The vegetable oil extraction industry is the primary contributor of volatile organic compound emissions in the food industry. The annual hexane loss in the soybean oil extraction process alone in the US could be as high as 210 - 430 million liters. There are growing health concerns and increased environmental regulations regarding the use of hexane in vegetable oil extraction. Exposure to hexane at 15 ppm/day for three months has been shown to cause peripheral nerve damage, and hexane is also a potential hazardous explosive material. The U.S. Environmental Protection Agency (EPA) established regulations on hexane emission due to growing environmental concerns. There is a pressing need for more sustainable extraction method as an alternative to hexane.
The overall goal of this research is to identify the fundamental processes that will allow us to develop a robust surfactant-based bio-oil extraction process, including a fundamentally-based model for design of microemulsion extraction processes for a range of bio-oils. The work proposed here would, for the first time, provide a quantitative understanding of fundamental processes influencing the bio-oil extraction by the aqueous surfactant-based method, and further would provide a new quantitative model which can be used for making a priori predictions of extraction performance under realistic conditions. The resulting model could be used to design surfactant-based extraction systems for a wide range of plants and oilseeds, which is not available at present. The results of this work have the potential to be transformative, in that they will significantly advance the way in which bio-oils are extracted, resulting in an industry-wide replacement of environmentally-hazardous solvent-based methods with more environmentally-benign aqueous surfactant-based methods. Aqueous processing of oilseed extraction is preferred over hexane because it is environmentally friendly, safe and produces oil with superior quality. While enzyme-based extraction of soybean oil can achieve greater than 90% oil extraction efficiency, the enzyme-assisted extraction process requires long incubation time, high temperature and produces stable emulsions, which are not desirable in industrial scale. To address these challenges, this project will utilize bio-compatible extended-surfactant systems to achieve high oil extraction efficiency while avoiding stable emulsion formation. The work will then be extended to test micro-algae oil extraction to validate the versatility of the surfactant-assisted aqueous extraction method and process model. This project will study the mixture of a branched surfactant with a novel extendedsurfactant (surfactants with an intermediate polarity groups inserted between the head and the tail of the surfactant molecule). Extended-surfactants consistently showed ultralow interfacial tension with a wide range of vegetable oils, but they require very high salt concentration to achieve optimum performance. By mixing extended-surfactants with a hydrophobic and branched surfactant, the requires salinity will be reduced while the branching will decrease the surfactant tail-tail interaction, allowing better oil penetration, thereby improving the extraction efficiency.
The results of this innovative research potentially benefit to the society, as well as education initiatives designed to enhance the learning experience of undergraduate and graduate students at the University of Oklahoma. The new application of surfactant in oilseed extraction and understanding the fundamental science of this approach will be integrated into a colloids and surface science course at the University of Oklahoma, which has attracted a number of undergraduate and graduate students from multi engineering disciplines (i.e. chemical engineer, chemistry, environmental engineer and science). In addition, the developed aqueous surfactantbased oil extraction prediction model resulting from this research will be submitted to the K-Gray Engineering Pathway Digital Library, allowing course shareware among universities. The developed model will provide an interactive educational module where students can explore the fundamental mechanisms involved in oilseed extraction as well as applying the model in advanced chemical process design.
