Grantee Research Project Results
2005 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, 2004 through December 31, 2005
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 objective of this research project is 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 quantify the solubilization capacity, interfacial tension, characteristic length, and interfacial rigidity.
The specific objectives of the project are to:
- Use the surfactant formulations with the most promising results for hexadecane and motor oil 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, and 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 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, and estimate and compare the cost of the different alternative solvents and assess its economic feasibility.
- Develop a generl 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:
VOCs, such as percholoroethylene (perc), hexane, and chloroform, have been widely used as conventional solvents in cleaning technologies and vegetable oil extraction. 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 a high cleaning efficiency. 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 ultra low interfacial tension (IFT) and ultra high solubilization properties of these systems. In this project, we focus on textile cleaning process and vegetable oil extraction applications.
In the textile cleaning process, special kinds of fabric (e.g., wool, silk, linen, and rayon) and special stains (highly hydrophobic oils) make dry cleaning desirable. The primary chemical solvent used in dry cleaning is perc. Perc is known to cause many adverse health effects and has been labeled as a probable human carcinogen. During the dry cleaning operation, Perc emissions can easily contaminate both air and water phases and thus cause environmental concern. In addition, significant energy consumption is required in the solvent regeneration step. 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 of this research, 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. Results to date show that, although conventional surfactants alone are not able to form middle phase microemulsion with these highly hydrophobic oils, mixtures of conventional surfactants and hydrophilic/lipophilic linkers are successful. We also observe that the use of hydrophilic/lipophilic linkers improved our formulations and make the resulting extraction systems more robust. In addition, we successfully used newly produced alkyl propoxylated sulfates, known as extended surfactants (surfactants with “internal” linkers), in formulating such systems. These extended surfactants reduce the amount of surfactant required and reduce the complexity of the formulation while still producing ultra low IFT.
After successfully formulating low IFT-microemulsion systems, we applied them to detergency tests 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 were stained on 65/35 polyester-cotton blend fabric. Our microemulsion formulations were used in two different approaches: as a pretreatment solution (4.67 wt% concentrate surfactant concentration) and as a washing solution (0.2 wt% surfactant concentration). The results show that more than 80 percent of hexadecane is removed by using the pretreatment method. As a washing solution, our microemulsion formulation removed oil from fabric up to 81 percent at very low surfactant concentration (0.2 wt%). Compared to a commercial detergent, it is very encouraging to see that both of our microemulsion formulation approaches show a superior detergency performance.
For vegetable oil extraction, conventional hexane extraction of edible oil from oilseeds is of growing concern because of its environmental impact, energy cost, and worker exposure. A number of alternative technologies have been evaluated for oilseed extraction, including extraction by enzymatic mixtures or other VOCs. VOCs are mostly toxic and carcinogenic substances. The goal of our project is to formulate environmentally friendly surfactant-based formulations that maintain the simplicity of operation and achieve reduction in energy consumption. The results to date for vegetable oil extraction are likewise very promising. We have successfully achieved two main goals. First, we have been able to formulate simple aqueous-extended-surfactant-based formulations that are able to achieve utralow IFT (as low as 0.009 mN/m). At low concentrations (i.e., less than 0.5 wt%), extended-surfactants have shown the ability to produce ultralow IFT with a wide range of vegetable oils, including canola, peanut, soybean, corn and olive oils at room temperature, and without additives. To our knowledge, we are the first to achieve this result, which shows great promise for use in edible oil extraction. At low surfactant concentrations, ambient temperature, and without additives, extended-surfactant systems show 90 percent of peanut oil yield, which is very competitive with hexane-based and aqueous enzymatic methods. Second, we have successfully formulated linker-extended-surfactant formulations that can form Winsor Type III and Winsor Type IV with triolein and a wide range of vegetable oils (corn, canola, soybean, peanut, and olive) at ambient temperature and without co-oils and/or alcohols. To our knowledge, we are the first to report this result. The formation of Winsor Type III microemulsion at room temperature without addition of co-oils and/or alcohols have been extremely challenging for decades. In the next stage of our research, we will use the linker-extended-surfactant formulation to test with the vegetable oil extraction.
In summary, the results to date are very encouraging for using surfactant-based microemulsions for organic solvent replacement in dry cleaning and vegetable oil extraction.
Future Activities:
The following activities will be performed in the next year:
- Study the effects of the extended surfactant-linker-based microemulsion and the mixture conventional- and extended-surfactant microemulsion systems on phase behavior, and characterize the interfacial properties such as IFT, characteristic length, and interfacial rigidity.
- Perform detergency tests for promising aqueous-based microemulsion formulations with hexadecane and motor oil.
- Elucidate the dominant detergency mechanism to have a better understanding and improve detergency performance.
- Apply our surfactant formulations to hard surface cleaning.
- Study effects of other variables on the efficiency of vegetable oil extracted, namely, the effect of agitation speeds, solid to liquid ratio, and extraction and centrifugation time.
- Perform aqueous-extended-surfactant based experiments on various vegetable seeds, including canola, soybean, and olive seeds, to prove the universal capability of the method.
- Study the linker-extended-surfactant system in vegetable oil extraction in comparison to the extended-surfactant system.
- Perform oil quality test.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 11 publications | 2 publications in selected types | All 2 journal articles |
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Type | Citation | ||
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Acosta EJ, Nguyen T, Witthayapanyanon A, Harwell JH, Sabatini DA. Linker-based bio-compatible microemulsions. Environmental Science & Technology 2005;39(5):1275-1282. |
R830903 (2005) |
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Supplemental 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, Chemicals, Technology, Technology for Sustainable Environment, pollution prevention, Environmental Engineering, 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
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.