Grantee Research Project Results
2006 Progress Report: Nanostructured Microemulsions as Alternative Solvents to VOCs in Cleaning Technologies and Vegetable Oil Extraction
EPA Grant Number: R830903Title: Nanostructured Microemulsions as Alternative Solvents to VOCs in Cleaning Technologies and Vegetable Oil Extraction
Investigators: Sabatini, David A. , Harwell, Jeffrey H. , Witthayapanyanon, Anuradee , Do, Linh
Institution: University of Oklahoma
EPA Project Officer: Aja, Hayley
Project Period: January 1, 2003 through December 31, 2005 (Extended to January 13, 2007)
Project Period Covered by this Report: January 1, 2005 through December 31, 2006
Project Amount: $329,655
RFA: Environmental Futures Research in Nanoscale Science Engineering and Technology (2002) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
Objective:
The goal of this project is to develop and evaluate non-toxic, non-volatile, and biodegradable oil extraction. The specific objectives of the research project are to:
- Formulate microemulsion systems for motor oil and triolein. This work will identify specific surfactant molecules and linkers, concentration of these additives, optimization of the system based on cost per amount of oil solubilized and quantifying the solubilization capacity, interfacial tension, characteristic length and interfacial rigidity.
- Use the surfactant formulations with the most promising results for hexadecane and motor oil found in Objective 1 to dissolve a film of this oil deposited on a metal surface and fabric. Measure the amount of oil solubilized versus time under different shear rate conditions. Propose a model to explain the data based on different mass transfer mechanism for nanostructured fluids. Compare the results with volatile organic compound (VOC) solvents.
- Use the surfactant formulations with the most promising results for triolein in vegetable oil extraction. Indicate the fraction of oil removed and compare it with water and hexane extraction. Investigate and compare the quality of the oil obtained under the different systems. Correlate the fraction of oil removed versus the interfacial tension (IFT) of the equilibrium microemulsion system and formulate a dynamic model for oil detachment. Improve surfactant formulations and apply to vegetable oil such as peanut oil, soybean oil and canola oil etc. Estimate and compare the cost of the different alternative solvents and assess its economic feasibility.
- Develop a general model that will correlate oil solubilization/displacement with the nanoscale interfacial properties of microemulsion system (interfacial tension, characteristic length, interfacial rigidity, and interfacial curvature) and the flow shear conditions of the system.
Progress Summary:
VOC solvents, such as percholoroethylene (perc), hexane, and chloroform, have been used widely as conventional solvents in cleaning technologies and vegetable oil extraction for decades. These organic solvents are classified as hazardous and probable carcinogenic substances. Although environmental contamination and health risks occur when using organic solvents in numerous operations, these organic solvents still are used because of their ready availability and high cleaning efficiency. Therefore, the goal of this research is to find aqueous-based surfactant microemulsions that can replace VOC solvents with environmentally friendly systems.
Microemulsions contain nanosized aggregates that can be used as extracting entities at the nanoscale level. This project uses nanoscale microemulsion environments as receptors for oily soils. Microemulsions play a key role in solvent replacement because of the ultralow IFT and ultrahigh solubilization properties of these systems. In this project, we focus on a textile cleaning process and vegetable oil extraction applications.
In cleaning processes such as detergency, the removal of stains (highly hydrophobic oils) from some special types of fabric (e.g., wool, silk, linen, and rayon) can be a challenging task because of the strong attachment between dirty stains and fabric. Because of this reason, dry cleaning or cleaning using organic solvent has become popular. The primary organic solvent used in dry cleaning is perchloroethylene (perc), which is known to cause many adverse health effects such as headaches, nausea, and disorders of the central nervous system. Moreover, it also has been labeled as a probable human carcinogen. During the dry cleaning operation, perc emissions easily can contaminate the air and water and thus cause environmental concern. The purity of organic solvent is the key to success. The organic solvent must be maintained at a high purity to achieve the maximum cleaning efficiency. As a result, a large amount of energy is consumed in the solvent regeneration step. Therefore, in this project, we seek an alternative to perc-based dry cleaning by developing aqueous-based microemulsions for cleaning oily soils.
In the first part, our target is to formulate microemulsion systems providing a low IFT and high oil solubilization capacity with highly hydrophobic oils such as hexadecane and motor oil. The result shows that the conventional surfactant and alcohol system is not able to produce the low IFT value and also cannot form a nice middle phase microemulsion with these highly hydrophobic oils, whereas an extended surfactant, surfactant with internal linkers, makes them possible. The extended surfactant not only produces an ultralow IFT value at the dilute surfactant concentration but also has extremely low critical micelle concentration and critical microemulsion concentration values. The drawback of the extended surfactant microemulsion is the long equilibration time (2 weeks), which will not be possible for many cleaning processes requiring a short contact time (i.e., detergency, hard surfactant cleaning, and solvent extraction, etc.). Therefore, we propose either adding linkers or cosurfactant to speed up its equilibrium. The addition of linkers or cosurfactant in the formulation reduces an equilibration time by minutes or sometimes hours.
Furthermore, after we are successful in formulating low IFT-microemulsion systems, we then will apply them to a detergency test based on the hypothesis that the low IFT and high solubilization properties of surfactant microemulsion can promote two major mechanisms of oil removal in detergency (roll-up and snap-off mechanisms). Hexadecane and motor oil are chosen and stained on 65/35 polyester-cotton blend fabric. Our microemulsion formulations are used in two different approaches, as a pretreatment solution (0.07 M or 4.67 wt % concentrate surfactant concentration) and as a washing solution (0.003 M or 0.2 wt % surfactant concentration). The results show that more than 80 percent of hexadecane is removed by using a pretreatment method. Additionally, it is worth pointing out that the high cleaning efficiency of our aqueous-based microemulsion is maintained even for a heavy duty load and also overcomes the cleaning performance of dry cleaning without the solvent purifying step. This emphasizes a possibility to use the aqueous-based microemulsion, which is an environmentally friendly and energy saving system, to replace organic solvents used in cleaning applications. Another exciting result is shown by using microemulsion formulation as a washing solution. Our microemulsion solvent can remove oil from fabric up to 81 percent using a very low surfactant concentration (0.2 wt %). Compared to an organic solvent and a commercial detergent, it is very encouraging to see that both of our microemulsion formulation approaches show a superior detergency performance.
Edible oils are obtained from oilseed by either hexane extraction or the combination of mechanical pressing and hexane extraction. In 2001, the U.S. Environmental Protection Agency promulgated regulations on hexane emission because of the growing environmental concern. Additionally, the crude oil produced by hexane has a high content of free fatty acid, wax, and unsaponifiable matter, and also suffers from dark greenish-brown color. The goal of our project is to formulate environmentally friendly surfactant-based formulations that maintain the simplicity of operation and reduce energy consumption while maintaining performance.
We have accomplished two ultimate goals for this project: (1) the successful design of vegetable oil microemulsions using environmentally benign formulations at ambient conditions; and (2) achievement of 93 percent of peanut oil extraction by using a dilute aqueous extended surfactant-based system. From surfactant selection studies, we have shown that among different classes of extended surfactants studied, the linear alkyl-propoxylated (PO)-ethoxylated (EO)-sulfate class of surfactants is most suitable for vegetable oil extraction because it produces the lowest IFT. Additionally, the C10-18PO-2EO-sulfate exhibits the best performance for vegetable oil extraction in terms of IFTs and salinity.
In this progressive report, we have evaluated the quality of vegetable oil extracted by using an aqueous extended surfactant-based method. We compare the crude oil quality obtained by our method to that by the hexane method. We also look at the effects of different processing parameters on vegetable oil extraction efficiency, which are surfactant concentrations, extraction times, shaking speeds, solid-to-liquid ratios, and salinity concentrations. These are important designed variables in our future pilot-scale study. In the progressive study, we have found that surfactant concentrations and salt concentrations have major impact on vegetable oil extraction efficiency. Using too low liquid-to-solid ratios increases the viscosity of the mixture and leads to poor surfactant and oilseed contact. From the evaluation of crude oil quality, it was shown that our method offers crude oil quality in terms of free fatty acid content compared to the hexane method. In the next step, we plan to study the pilot-scale and design a continuous extraction process and evaluate the economic feasibility of this technology.
Future Activities:
We will: (1) apply microemulsion knowledge received from hexadecane microemulsion study to complex hydrophobic oils such as motor oil; (2) perform detergency tests for promising aqueous-based microemulsion formulations with motor oil; (3) elucidate the dominant detergency mechanism to have a better understanding and improve detergency performance; (4) perform a pilot-scale study in a continuous manner for vegetable oil extraction; (5) study effects of other variables on the efficiency of vegetable oil extracted (i.e., the effect of agitation speeds, solid-to-liquid ratio, and extraction and centrifugation time in the continuous process); (6) perform aqueous extended surfactant-based experiments on various vegetable seeds, including canola, soybean, and olive, to prove the universal capability of the method; (7) study the effect of recycle extended surfactant solution on the vegetable oil extraction; and (8) perform an oil quality test.
Journal Articles:
No journal articles submitted with this report: View all 11 publications for this projectSupplemental Keywords:
microemulsion, interfacial tension, linkers, extended surfactant, textile cleaning, vegetable oil extraction,, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, TREATMENT/CONTROL, POLLUTANTS/TOXICS, Sustainable Industry/Business, Environmental Chemistry, Sustainable Environment, Technology, Chemicals, Technology for Sustainable Environment, Environmental Engineering, pollution prevention, clean technologies, cleaner production, environmental sustainability, nanotechnology, VOC removal, alternative materials, alternative solvents, vegetable oil extraction, biodegradable materials, Volatile Organic Compounds (VOCs)Relevant Websites:
http://www.cems.ou.edu/iasr Exit
http://cees.ou.edu/ Exit
http://coecs.ou.edu/soonercity/sabatini/ Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.