![[logo] US EPA](https://webarchive.library.unt.edu/eot2008/20081107120948im_/http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
Final 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. , Do, Linh , Harwell, Jeffrey H. , Witthayapanyanon, Anuradee
Institution: University of Oklahoma
EPA Project Officer: Lasat, Mitch
Project Period: January 1, 2003 through December 31, 2005 (Extended to January 13, 2007)
Project Amount: $329,655
RFA: Environmental Futures Research in Nanoscale Science Engineering and Technology (2002)
Research Category: Nanotechnology
Description:
Objective:The objectives are to:
- Formulate microemulsion systems for motor oil and triolein. This work will identify specific surfactant molecules and linkers and the concentration of these additives ; will optimization of the system based on cost per amount of oil solubilized; and will quantify the solubilization capacity, interfacial tension (IFT), characteristic length and interfacial rigidity.
- Use the surfactant formulations with the most promising results for hexadecane and motor oil found in Objective 1, and 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 mechanisms 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 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, canola oil, etc. Estimate and compare the cost of the different alternative solvents and assess their economic feasibility.
- Develop a general model that will correlate oil solubilization/displacement with the nanoscale interfacial properties of a microemulsion system (interfacial tension, characteristic length, interfacial rigidity, and interfacial curvature) and with the flow shear conditions of the system.
VOCs, such as percholoroethylene (perc), hexane, and chloroform, have been widely used as conventional solvents in cleaning technologies and vegetable oil extraction for decades. These organic solvents are classified as hazardous, flammable, and probable carcinogenic substances. While environmental contamination and health risks occur when using organic solvents in numerous operations, these organic solvents are still used due to their ready availability and high cleaning efficiency. Therefore, the goal of this project is to find a high-efficiency and environmentally friendly cleaning solution that can be used to replace VOC solvents.
Aqueous-based surfactant microemulsions are an outstanding candidate for this project, since microemulsions offer low IFT and high solubilization properties, which are key factors in enhanced oil removal. The remarkable advantages of using alternative aqueous-based microemulsions (nano scale surfactant aggregates) have been evaluated in two applications, the textile cleaning process and vegetable oil extraction. In the textile cleaning process, a target study is to compare the removal of highly hydrophobic oils, which strongly deposit on fabric, using microemulsion formulations as an alternative to the dry cleaning process. Hexadecane and motor oil are selected to be model oils due to their highly hydrophobic nature. Various surfactants are quickly scanned based on a dynamic IFT (dyn IFT) technique, with the resulting microemulsion properties further evaluated based on an equilibrium phase study. The result shows that conventional surfactants do not achieve low dynamic IFT values during 20 -minute measurements (IFT around 10-1–101 mN/m) and do not form middle phase microemulsions without the addition of alcohol or additives, while extended surfactants offer the ultra low dynamic IFT values (10-2–10-3 mN/m) within 5 minutes. These ultra-low IFT values correspond to the presence of middle-phase microemulsion. Moreover, the low IFT value (10-2 mN/m) of an extended surfactant is initially attained when surfactant concentration reaches the critical microemulsion concentration, or CμC, of the surfactant (on the order of 300 ppm).
Furthermore, the detergency performance of our microemulsion formulations is illustrated in comparison to water, commercial detergent product (CP), and dry cleaning solvent (perc). Our microemulsion solutions achieve an 80% removal of hexadecane stains. Although the cleaning efficiency of our formulation has not yet achieved the detergency performance of perc yet (93% vs. 91%), this result shows a possibility of using our aqueous-based solvent to replace the organic solvent. Another promising result is that our microemulsion formulation systems demonstrate a superior detergency performance when compared to a commercial detergent (85 versus 77%, respectively). Then we subsequently demonstrate a nice relationship between the IFT value, surfactant concentration, and detergency performance. The maximum oil removal is observed at the Cμ;C, where the IFT of a system drops below 10-2 mN/m. It must be emphasized that the amount of extended surfactant used to obtain a maximum detergency is extremely low compared to a commercial detergent product used in a standard washing machine (0.03 wt% vs. 0.3 wt%). This dilute surfactant formulation is not only desirable from an economical perspective, but also is more environmental friendly, as it results in less surfactant discharged to the environment. Additionally, our aqueous-based microemulsions also show an exciting result in use with a heavy duty load washing machine. Organic solvent (perc) exhibits very high cleaning efficiency at the low solvent loading rate, but its performance gradually decreases when the perc contains more oily soil in solution (perc is less pure). This result is expected because in dry cleaning, the organic solvent must be maintained at high purity to achieve the maximum detergency performance, whereas our microemulsion solution retains the same cleaning efficiency even at the high solvent loading rate. The result supports the idea of using the microemuls ion solution as an alternative solvent. Besides cleaning performance, the use of aqueous-based microemulsion also reduces the energy cost used to purify the organic solvent in dry cleaning.
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 due to growing environmental concern. Additionally, the crude oil produced by hexane has high contents of free fatty acid, wax and unsaponifiable matter, and also suffers from a dark greenish-brown color (Juliano, 1985). 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: successfully design vegetable oil microemulsions using environmentally benign formulations at ambient conditions and successfully achieve 93–96% of peanut oil and canola oil extraction by using a dilute aqueous extended-surfactant based system. From our work, we have found that it might not be feasible to extract soybean oil by using this method, since soybean seeds contain high amounts of lecithin, which acts as a surfactant and stabilizes the macroemulsion formed during the extraction process. From surfactant selection studies, we have shown that among different classes of extended-surfactants studied, the linear alkyl-propoxylated-ethoxylated-sulfate class of surfactants is most suitable for vegetable oil extraction, since 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 work, 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—surfactant concentrations, extraction times, shaking speeds, solid-to-liquid ratios, and salinity concentrations—on vegetable oil extraction efficiency. These are important design variables in our future pilot-scale study. We have found that surfactant concentrations and salt concentrations have major impacts on vegetable oil extraction efficiency. Using too low of a liquid-to-solid ratio increases the viscosity of the mixture and leads to poor surfactant and oilseed contact. On the other hand, using too high of a solution-to-solid ratio causes less particle collision, leading to poor extraction efficiency. From the evaluation of crude oil quality, it was shown that our method offers better crude oil quality in terms of free fatty acid content compared to the hexane method. We have successfully achieved the goal to prove the concept of using aqueous surfactant based method to extract vegetable oils.
Reference:
Juliano BO. Rice bran. In: Juliano BO, ed. Chemistry and Technology, 2nd edition. MN: The American Association of Cereal Chemists, 1985, pp. 647-687.
Journal Articles on this Report: 2 Displayed | Download in RIS Format
| Other project views: | All 10 publications | 2 publications in selected types | All 2 journal articles |
| Type | Citation | ||
|---|---|---|---|
|
|
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) R830903 (Final) |
|
|
|
Witthayapanyanon A, Acosta EJ, Harwell JH, Sabatini DA. Formulation of ultralow interfacial tension systems using extended surfactants. Journal of Surfactants and Detergents 2006;9(4):331-339. |
R830903 (Final) |
|
microemulsion, interfacial tension, linkers, extended surfactant, textile cleaning, vegetable oil extraction,
,
POLLUTANTS/TOXICS, INTERNATIONAL COOPERATION, TREATMENT/CONTROL, Sustainable Industry/Business, Scientific Discipline, RFA, Technology for Sustainable Environment, Sustainable Environment, Technology, Chemicals, Environmental Engineering, Environmental Chemistry, pollution prevention, nanotechnology, environmental sustainability, nanostructured microemulsions, cleaner production, Volatile Organic Compounds (VOCs), clean technologies, VOC removal, alternative solvents, vegetable oil extraction, alternative materials
Relevant Websites:
http://www.cems.ou.edu/iasr
http://cees.ou.edu/
http://www.coe.ou.edu/sabatini/
Progress and Final Reports:
2005 Progress Report
2006 Progress Report
Original Abstract