Direct Force Measurement between Surfaces Coated with Hydrophobic Polymers in Aqueous Solutions and the Separation of Mixed Plastics by Flotation

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dc.contributor.authorMa, Ninien
dc.contributor.committeechairYoon, Roe-Hoanen
dc.contributor.committeememberAdel, Gregory T.en
dc.contributor.committeememberLuttrell, Gerald H.en
dc.contributor.departmentMining and Minerals Engineeringen
dc.date.accessioned2014-03-14T20:50:39Zen
dc.date.adate2009-01-09en
dc.date.available2014-03-14T20:50:39Zen
dc.date.issued2008-08-27en
dc.date.rdate2010-12-22en
dc.date.sdate2008-12-22en
dc.description.abstractFroth floatation is an important process used in the mining industry for separating minerals from each other. The separation process is based on rendering a selected mineral hydrophobic using an appropriate hydrophobizing reagent (collector), so that it can selectively attach onto the surfaces of a rising stream of air bubbles. Thus, controlling the hydrophobicity of the minerals to be separated from each other is of critical importance in flotation. If one wishes to separate plastics from each other by flotation, however, it would be necessary to render a selected plastic hydrophilic and leave the others hydrophobic. In the present work, the possibility of separating common plastics from each other by flotation has been explored. While water contact angle is the most widely used measure of the hydrophobicity of a solid, it does not give the information on the kinetics of flotation. Therefore, the forces acting between the surfaces coated with different hydrophobic polymers (or plastics) in water were measured using the Atomic Force Microscope (AFM). The results obtained with polystyrene, polymethylmethacryrate (PMMA), polypropylene (PP), and Teflon showed the existence of long-range attractive forces (or hydrophobic force) that cannot be explained by the classical DLVO theory. The surface force measurements were conducted in pure water and in solutions of surfactant (alkyltrimethylammonium chloride) and a salt (NaCl). In pure water, the attractive forces were much stronger than van der Waals force. In the presence of the surfactant and NaCl, the long-range attraction decreased with increasing concentration and the alkyl chain length. A series of contact angle measurements were conducted to determine the hydrophobicity of polystyrene (PS), polyvinyl chlorite (PVC), and polymethylmethacrylate (PMMA) in the presence of different wetting agents (surfactants). The results show the possibility of separating plastics from each other by flotation, and a series of microflotation tests conducted on PS and PVC showed promising results.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-12222008-163505en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-12222008-163505/en
dc.identifier.urihttp://hdl.handle.net/10919/36399en
dc.publisherVirginia Techen
dc.relation.haspartNini_Ma_Thesis.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectplastic recyclingen
dc.subjectflotation of plasticsen
dc.subjectDLVO theoryen
dc.subjectfroth flotationen
dc.subjectcontact angleen
dc.subjectsurface forceen
dc.subjecthydrophobic polymersen
dc.titleDirect Force Measurement between Surfaces Coated with Hydrophobic Polymers in Aqueous Solutions and the Separation of Mixed Plastics by Flotationen
dc.typeThesisen
thesis.degree.disciplineMining and Minerals Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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