last update: July 05, 2000
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STC-ERSP Program Details Principal Investigator: K.L. Roberts Project Title: Surfactant/Supercritical CO2 Cleaning of Contaminated Substrates (#20) Phone/Fax: (336) 334-7564/(336) 334-7904 E-mail: kroberts@ncat.edu Research Plan Connectivity Outreach Components Requested Budget Allocation - Year 1 Plans for Additional Funding Research Plan Overall objectives Roberts (A&T) proposes to determine the performance of various surfactant/supercritical CO2 systems for the removal of contaminant substances from metallic surfaces and natural fibers. By continuing previous work with the cleaning of metallic substrates with supercritical hydrocarbon/surfactant mixtures, the phase equilibria associated with surfactant/supercritical CO2 systems will first be characterized. The effect of temperature, pressure, surfactant molecule and contaminant types (i.e., polar, ionic, oily) on phase equilibria will then be determined. Finally the cleaning performance of the supercritical fluid/surfactant mixtures will be evaluated as functions of temperature, pressure, surfactant molecule, composition and cleaning time. Relation to overall objectives of the Center The utilization of surfactants/supercritical fluid cleaning processes has found industrial application in the removal of contaminants from high precision metal parts. Current cleaning technologies use high amounts of chlorinated liquid hydrocarbons that have problems such as high disposal costs and environmental problems such as ground-level ozone formation and ozone layer depletion. The use of surfactant/supercritical CO2 mixtures for metallic substrate cleaning could potentially replace chlorinated organic-based cleaning technologies such as dry cleaning. With minor variations in system pressure, surfactants could be recovered leading to a minimization of surfactant requirements. This project will require a fundamental understanding of supercritical fluid/surfactant systems and the surface cleaning mechanisms for these systems. Approach and timelines: Year 1- Year 5 Years 1-2To implement cleaning experiments using model surfactant compounds such as Aerosol OT, lecithin and didodecyldimethylammonium bromide and supercritical CO2. Reverse micelle mixtures with H2O and respective phase equilibria will be determined. The effect of temperature, pressure, surfactant molecule, contaminants (i.e., polar, ionic, oily) and composition on the phase equilibria of the surfactant/supercritical fluid systems. Preliminary phase equilibria models will be developed using basic cubic equations of state. Years 2-3 The performance of the above stated supercritical CO2/surfactant mixtures will be determined for contaminated metallic and fibrous substrates. The performance of the mixtures will be analyzed using the predictive models of surfactant/supercritical CO2 equilibria. The analysis of the reverse micelle cleaning systems will be carried out utilizing the techniques of Carbonell and Grant (NCSU). Year 2-5 The best surfactant/supercritical fluid mixtures for cleaning will be identified. New applications for these systems will be explored including (but not limited to) the use of biosurfactants, the cleaning of industrially important materials (i.e., silicon & GaAs wafers, polymeric substrates, composite materials). Thrust area of this proposal Thrust Area C: Rate Processes Connectivity Collaborators, multi-institutional, multi-disciplinary components The analysis of the cleaning mechanisms for surfactant/supercritical fluid cleaning would utilize the well-establish techniques of Carbonell and Grant (NCSU). Novel surfactant compounds produced by DeSimone (UNC-CH) will be analyzed in the cleaning systems. Comparisons between the liquid CO2/surfactant cleaning techniques of DeSimone (UNC-CH) and Carbonell (NCSU) and this group's supercritical CO2/surfactant cleaning will be made for the removal of contaminants from various substrate types. The measurement of thermophysical properties (i.e., heat of adsorption, phase transition temperature, specific volumes, etc.) will be carried out in the Thermophysical Property Measurement Laboratory at North Carolina A&T with Kabadi (NC A&T). Related work in other thrust areas This project will make strong connections with Thrust Area A (Colloid and Surface Science in Compressible Media) and Thrust Areas B (Molecular Thermodynamics and Computer Simulations) in the application of colloid/surface science and molecular thermodynamics to advanced cleaning processes. The researchers in Thrust Area A (Colloid/Surface Science) will use the surfactant/CO2 systems for the examination of micelle formation in high-pressure systems. The researchers in Thrust Area B (Molecular Thermodynamics and Computer Simulations) will analyze the surfactant/supercritical CO2 systems in an attempt to more accurately characterize and predict the phase equilibria of these systems. Sharing of resources (students, supplies, equipment, etc.) The student responsible for this project will share phase equilibria data and surfactant compounds with other groups for analysis and model analysis. The student will be intimately involved in the understanding of relationships between surfactant properties and system equilibria on cleaning efficiency. The student will work closely with the PI. Outreach Components Suggested K-12 Outreach Ideas Roberts and the student will be involved in community outreach activities such as the AIChE Outreach for K-12 students, the National Society of Black Engineers Pre-College Initiative program (6-12), and Guilford County Schools of NC. The importance of surfactants in our daily lives and in the manufacturing of common consumer items will be presented. Requested Budget Allocation - Year 1 Personnel salaries
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