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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Behavior of perfluorochemicals on solid surfaces: sorption and mineralization processes

Wang, Fei, 王飞 January 2013 (has links)
The study evaluated the sorption behavior of PFOS and PFOA on γ-alumina and boehmite. The results of adsorption kinetics on γ-alumina and boehmite show that it takes 48 h to reach equilibrium. The adsorption isotherms reveal the maximum adsorption capacities of PFOS and PFOA are different due to their different functional groups. An increase in pH leads to a decrease in PFOS and PFOA adsorption on alumina, which may be attributed to the reduction in electrostatic interaction. The adsorption of both PFOS and PFOA decreases with an increase in ionic strength due to the compression of the electrical double layer. The different sorption level of PFC on γ-alumina and boehmite indicated that the crystal phase of mineral also affected the sorption process. The sorption of PFOS and PFBuS on boehmite was significantly retarded by the competitive sorption of humic acid (HA), implying that PFOS and PFBuS are likely more mobile in water and groundwater systems enriched with HA. The sorption behavior of PFOS and PFBuS on the HA-modified boehmite surface was also found to differ due to their different chain lengths. In addition, the results revealed that the sorption of PFOS and PFBuS on HA-modified boehmite is pH-dependent. The isotherm study of FOSA on three types of microplastics indicated that hydrophobic interaction plays a dominant role in the sorption process and the molecule structure of different microplastics can affect its sorption level. The PFOS sorption isotherm indicated that electrostatic interaction plays an important role in the PFOS sorption process on PE and PS while its sorption on PVC was electrostatic interaction independent. The effects of pH and ionic strength indicated that electrostatic interaction plays an important role in PFOS sorption process. The kinetic study showed that the PCMAs had a rapid sorption towards PFAS species and the isotherm study indicated that hydrophobic interaction played an important role in the sorption process. The sorption of PFOS by the PCMAs was not significantly affected by the pH and slightly decreased with an increase in ionic strength. Moreover, the sorbent had showed excellent regeneration performance. Two main fluorine mineralization mechanisms leading to the substantial formation of CaF2 and Ca5(PO4)3F phases were observed. They had a close relationship with the thermal treatment condition and the PFOS content of the sludge. At low temperatures (300C -600C), CaF2 dominated in the product and increases in treatment time and temperature generally enhanced the fluorine transformation. However, at higher temperatures (700C -900C), increases in treatment time and temperature had a negative effect on the overall efficiency of the fluorine crystallization. The results suggest that in the high temperature environment there were greater losses of gaseous products such as HF and SiF4 in the transformation of CaF2 to Ca5(PO4)3F, the hydrolysis of CaF2, and the reaction with SiO2. The quantitative analysis also showed that when treating sludge with low PFOS content at high temperatures, the formation of Ca5(PO4)3F may be the primary mechanism for the mineralization of the fluorine in PFOS. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy
2

Reactions of some unsaturated fluorocarbon derivatives with organo compounds of phosphorus and nitrogen

Dawson, David S. January 1967 (has links)
Perfluorocyclobutene and 1,2-dichlorotetrafluorocylobutene react readily with diethylphosphine at 20° to give unstable mono-substitution products, 1-diethylphosphino-2-halotetrafluorocy-clobutenes. With tetramethyldiphosphine, low yields of 1,2-bis(dimethylphosphino)tetrafluorocyclobutene and trifluorodimethylphosphorane are obtained from the chloro- and perfluoro-butenes respectively. Diphenylphosphine also gives the 1,2-disubstituted product at 20°, from perfluorocyclobutene only. This olefin interacts with tetraphenyldiphosphine (130 ) to give 1-diphenylphosphinotrlfluorocyclobutenone (from 95% ethanol). Under identical conditions the chloro-butene reacts with the phenyl-phosphines to give trifluorodiphehylphosphorane and fluoro-diphenylphosphine oxide. Tetrakis (trifluoromethyl) diphosphlne on heating or ultra-violet irradiation reacts only very slightly, while bis(trifluoromethyl)phosphine is essentially inert towards the cyclobutenes. Dimethylamine readily adds to hexafluorobutyne-2 at 20° to give the 1:1 adduct, 2=dimethylamino-3-H-hexafluorobutene-2, the ratio of trans:cis isomers being 6.2:1. The cis isomer Is converted by distillation, but not by heating in a sealed tube, to the trans form. This latter isomer quickly achieves an equilibrium with the cis configuration on exposure to the air; at equilibrium, trans:cis ≈1.6:1. Hexafluorobutyne-2 reacts vigorously at 20° with a trimethylamine-water mixture. The major products of the complex reaction are a bis(hexafluorobutenyl) ether and trans-3-H-heptafluorobutene-2. When the reaction mixture is permitted to reach room temperature only slowly, the ether predominates. In the absence of water a high polymer of the butyne is slowly deposited. Chlorodimethylamine requires heating or ultra-violet irradiation to react with the butyne. The reaction is complex. At 85° (also on irradiation), the major product is the 1:1 adduct (100% cis); at 139°, trans-2-chloro-3-H-hexafluorobutene-2 predominates. Prolonged ultra-violet irradiation of a bis(trifluoromethyl)phosphine-hexafluorobutyne-2 mixture affords a mixture of 1:1 and 2:1 adducts. The expected 1,1,1,4,4,4-hexafluorobut-2-enyl derivatives, are obtained from the acetylene and diethylphosphine, diphenylphosphine and tetraphenyldiphosphine (130°). Tetra-methyldiphosphine gives a low yield of methyldifluorophosphine oxide. Triphenylphosphine vigorously catalyzes the polymerization of the butyne at -78°. ChlorodimethyIphosphine and hexa-fluorobutyne-2 afford trans-3-H-2-chlorohexafluorobutene-2 and trifluorodimethylphosphorane, while chlorodimethyIphosphine sulfide does not react on heating (106°) or ultra-violet irradiation. Tetramethyldiphosphine disulfide and iodine afford a loosely-bound 1:1 complex at 20° in the absence of excess iodine. Trifluoromethyl iodide does not react with the disulfide at 104° and only slightly on prolonged ultra-violet irradiation. DimethyIphosphine readily adds to hexafluoroacetone and 1,1,1-trifluoroaeetone, giving the 2-dimethylphosphino-isopropanols. The reaction with hexafluoroacetone also gives a 1:3 phosphine-acetone adduct. The product from 1,3-diehlorotetrafluoroacetone decomposes violently on reaching room temperature. The reactions of these fluorinated ketones with diphenylphosphine are more complex. The products include a mixture of 1:1 adducts; namely, 2=diphenylphosphino=isopropanols and isopropyldiphenyl-phosphine oxides. The latter probably are a result of an Arbuzov rearrangement of isopropoxydiphenyl-phosphines, Tetramethyl-diphosphine and hexafluoroacetone give a 1:3 adduct along with the 1:3 dimethylphosphine-hexafluoroacetone adduct. / Science, Faculty of / Chemistry, Department of / Graduate
3

Fluorocarbon derivatives of arsenic, sulfur and nitrogen.

Dhaliwal, Pritam Singh January 1966 (has links)
The disulfides RSSR (R = C₂H₅,C₆H₅ and CF₃ ) read with the diarsines R₂' As-AsR'₂ (R' = CH₃, CF₃) to give the compounds R'₂ As-SR. Dimethylarsine readily cleaves As-S and As-N bonds to yield a diarsine and the corresponding thiol and amine respectively. Unsymmetrical disulfides are obtained from the reaction of trifluoromethanesulfenyl-chloride with compounds containing arsenic-sulfur bonds. Trifluoromethanesulfenylchloride is readily reduced by dimethylarsine to yield chlorodimethylarsine and trifluo-romethanethio1. Tetramethyldiarsine is readily cleaved by trifluoromethanesulfenylchloride and trifluoromethanesulfonylchloride and yields trifluoromethyIthiodimethy-larsine and trifluoromethanesulfonyldimethylarsine respectively, in addition to chlorodimethylarsine, Tetramethyldiarsine also reacts with methanesulfonylanhydride to yield dimethylarsinomethanesulfonate. The cyclic f luoro-olefins RC= CR'CF₂(CF₂)n (n = 1, R = R' = F, R = R' = Cl, R = Cl, R' = H, and n = 2, R = R' = Cl, R = Cl, R' = H) react with secondary amines and arsines to give the compounds R"C= CR'CF₂ (CF₂) (R" = (C₂H₅ )₂N, (CH₃)₂ As), Methane thiol also reacts with these cyclic fluoroolefins (n = 1, R = R' = F, R = R'=Cl) to yield the compounds CH₃SC = CR'CF₂CF₂(R' = F, Cl). With 1-H-2-chlorotetrafluorocyciobutene, methane thiol affords a 1:1 adduct, which fails to eliminate hydrogen halide even at 150. With 1-H-2-chlorohexafluorocyclopentene and methane thiol, double bond migration occurs to yield 1-chloro-5-H-5-methylthiopentafluoroeyelopentene, 1-Ethyl-2-chiorotetrafluorocyciobutene affords 1-ethyl-2-methylthiotetrafluorocyciobutene and 1-ethyl-2-dimethyl-arsinotetrafluorocyciobutene when heated with methane thiol and dimethylarsine respectively. The rates of the above reactions are dependent on the nucleophilicity of the attacking nucleophile, the size of the fluoro-olefin ring and the electronegativity of the groups attached to the double bond. The chelating properties of the new ditertiary arsine, 1,2-dimethylarsinotetrafluorocyclobutene (difars) have also been investigated. Reaction with Fe(CO)₅ and Mo(CO)₆ under mild conditions yields the stable crystalline complexes [(difars) Fe(CO)₃] and[(difars) Mo(CO)₄], and under vigorous conditions all the carbon monoxide can be displaced from Mo(CO)₆. Difars displaces all the carbon monoxide from Ni(CO)₄ at 25°, but attempts to obtain coordination complexes of difars with Ni(II) salts have been unsuccessful. Platinum and palladium salts react with difars to yield stable crystalline complexes which can be formulated as [(difars) PtCl ₂]and [(difars) PdCl₂]. Rhodium trichloride trihydrate affords the complex [Rh (difars)₂Cl₂]Cl. Mercuric chloride and cadmium bromide yield the unstable complexes [(difars) HgCl₂] and [(difars)CdBr₂] / Science, Faculty of / Chemistry, Department of / Graduate
4

Quantification and partition of perfluorochemicals in Hong Kong wastewater sludge

Ma, Ruowei. January 2009 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 82-94). Also available in print.
5

Quantification and partition of perfluorochemicals in Hong Kong wastewater sludge /

Ma, Ruowei. January 2009 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 82-94). Also available online.
6

The thermodynamic properties of perfluoro-2-butyl-tetrahydrofuran /

Yarrington, Robert M. January 1958 (has links)
No description available.
7

Synthesis and characterization of molecules to study the conformational barriers of fluorocarbon chains

Niyogi, Sandip 05 1900 (has links)
Fluorocarbons are known to be stiffer than their hydrocarbon analogues, a property that underlines the extensive industrial application of fluorocarbon materials. Although there has been previous studies on the rotational barrier of molecules having fluorocarbon centers, a detailed systematic study is necessary to quantify flurocarbon stiffness. The molecules, Pyrene-(CF2)n-Pyrene, Pyrene-(CF2)n-F, Pyrene-(CH2)n-Pyrene and Pyrene-(CH2)n-H were therefore synthesized to enable the determination of the barrier to rotation of the carbon backbone in fluorocarbons. Conformational studies will be completed with steady-state and time-dependent emission spectroscopy.
8

Asymmetric fluorous biphasic catalysis based on perfluoroalkyl-BINOLs. / CUHK electronic theses & dissertations collection

January 2000 (has links)
Tian Yuan. / "September 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (p. 114-136). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.
9

A plasma polymerization investigation and low temperature cascade arc plasma for polymeric surface modification

Gilliam, Mary A., January 2006 (has links)
Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (April 25, 2007) Vita. Includes bibliographical references.
10

Intravenous administration of perfluorocarbon emulsions as a non-recompression therapy for decompression sickness /

Smith, Cameron Reid, January 2008 (has links)
Thesis (Ph.D.)--Virginia Commonwealth University, 2008. / Prepared for: Dept. of Anesthesiology. Bibliography: leaves 103-118. Also available online via the Internet.

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