Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Emulsions reversible

Removal of NAPL can present problems, particularly if emulsion is involved. Emulsion is an intimate mixture of two liquids not miscible with each other, as oil and water. Water-in-oil emulsions have water as an internal phase and oil as the external phase, whereas oil-in-water emulsions reverse the order. Oil-water separation is required prior to downstream treatment processes. Several specific oil removal technologies are presented below. [Pg.242]

Micro-emulsion, Reversed Micelles, Surfactants, Membranes, and Poly-electrolytes... [Pg.400]

MICRO-EMULSION, REVERSED MICELLES, SURFACTANTS, MEMBRANES, AND POLYELECTROLYTES... [Pg.402]

The two-emulsion (reverse) method has been used recently by Lee etal, [185] in an attempt to synthesize spherical zirconia particles under controlled conditions. In the overall scheme, a non-ionic surfactant (Span 85, Span 80, Span 40 or Arlacel 83, i.e. Sorbitan sesquioleate see below for the choice of surfactant) was dissolved in n-heptane. The HLB values of the surfactants varied in the range 1.8-6.7. Aqueous solutions of zirconium acetate or ammonia were added to two parts of the surfactant-oil phase combination the two had identical volumes. Reverse emulsions were prepared by subjecting the above to ultrasonic agitation, and the two emulsions thus produced were then mixed under stirring. The gel particles that formed in the process were separated by using a modified Dean-Stark moisture trap. Figure 4.4 presents the two-emulsion process in which the two complementary emulsions are mixed to obtain gel precipitates in the spherical droplets. [Pg.81]

Systematic reviews In a systematic review of all articles in which the use of parenteral fish oil to manage cholestasis during parenteral nutrition was reported, six case reports (10 patients) and two cohort studies (12 and 18 patients) were analysed [3 ]. Fish oil-derived emulsions reversed pre-existing cholestasis. [Pg.535]

One may rationalize emulsion type in terms of interfacial tensions. Bancroft [20] and later Clowes [21] proposed that the interfacial film of emulsion-stabilizing surfactant be regarded as duplex in nature, so that an inner and an outer interfacial tension could be discussed. On this basis, the type of emulsion formed (W/O vs. O/W) should be such that the inner surface is the one of higher surface tension. Thus sodium and other alkali metal soaps tend to stabilize O/W emulsions, and the explanation would be that, being more water- than oil-soluble, the film-water interfacial tension should be lower than the film-oil one. Conversely, with the relatively more oil-soluble metal soaps, the reverse should be true, and they should stabilize W/O emulsions, as in fact they do. An alternative statement, known as Bancroft s rule, is that the external phase will be that in which the emulsifying agent is the more soluble [20]. A related approach is discussed in Section XIV-5. [Pg.504]

Sensitizers as well as desensitizers form a reversal oxidoreduction system with silver halides, according to both pH and pAg of the photographic emulsion. But besides the specific influence of the emulsion, the efficiency of a sensitizing dye depends on many other factors such as its adsorption, its spectral absorption, the energetic transfer yield, the dye aggregate to the silver halide, and finally on its desensitizing property in... [Pg.78]

The teehniques of membrane extraetion permit an effieient and modern applieation of elassieal liquid-liquid extraetion (LLE) ehemistry to instmmental and automated operation. Various shorteomings of LLE are overeome by membrane extraetion teehniques as they use none or very little organie solvents, high enriehment faetors ean be obtained and there ai e no problems with emulsions. A three phase SLM system (aq/org/aq), where analytes are extraeted from the aqueous sample into an organie liquid, immobilized in a porous hydrophobie membrane support, and further to a seeond aqueous phase, is suitable for the extraetion of polar eompounds (aeidie or basie, ehai ged, metals, ete.) and it is eompatible with reversed phase HPLC. A two-phase system (aq/org) where analytes ai e extraeted into an organie solvent sepai ated from the aqueous sample by a hydrophobie porous membrane is more suitable for hydrophobie analytes and is eompatible with gas ehromatography. [Pg.244]

Microemulsion and miniemulsion polymerization processes differ from emulsion polymerization in that the particle sizes are smaller (10-30 and 30-100 nm respectively vs 50-300 ran)77 and there is no discrete monomer droplet phase. All monomer is in solution or in the particle phase. Initiation usually takes place by the same process as conventional emulsion polymerization. As particle sizes reduce, the probability of particle entry is lowered and so is the probability of radical-radical termination. This knowledge has been used to advantage in designing living polymerizations based on reversible chain transfer (e.g. RAFT, Section 9.5.2)." 2... [Pg.250]

In combination ATRP, the catalyst is again present in its more stable oxidized form. A slow decomposing conventional initiator e.g. AIBN) is used together with a normal ATRP initiator. Initiator concentrations and rate of radical generation arc chosen such that most chains arc initiated by the ATRP initiator so dispersities can be very narrow.290 The conventional initiator is responsible for generating the activator in situ and prevents build up of deactivator due to the persistent radical effect. Reverse or combination ATRP are the preferred modes of initiation for ATRP in emulsion or miniemulsion (Section 9.4.3.2).290 291... [Pg.491]

Emulsion polymerization has proved more difficult. N " Many of the issues discussed under NMP (Section 9.3.6.6) also apply to ATRP in emulsion. The system is made more complex by both activation and deactivation steps being bimolecular. There is both an activator (Mtn) and a deactivator (ML 1) that may partition into the aqueous phase, although the deactivator is generally more water-soluble than the activator because of its higher oxidation state. Like NMP, successful emulsion ATRP requires conditions where there is no discrete monomer droplet phase and a mechanism to remove excess deactivator built up in the particle phase as a consequence of the persistent radical effect.210 214 Reverse ATRP (Section 9.4,1,2) with water soluble dialky 1 diazcncs is the preferred initiation method/87,28 ... [Pg.498]

Many compounds can have a gelling action on poly (vinyl alcohol) solutions and in some cases the gels are thermally reversible. Gelling by means of polyhydroxy aromatic compounds has been of interest in photographic emulsions ( 7). [Pg.15]

PtRu nanoparticles can be prepared by w/o reverse micro-emulsions of water/Triton X-lOO/propanol-2/cyclo-hexane [105]. The bimetallic nanoparticles were characterized by XPS and other techniques. The XPS analysis revealed the presence of Pt and Ru metal as well as some oxide of ruthenium. Hills et al. [169] studied preparation of Pt/Ru bimetallic nanoparticles via a seeded reductive condensation of one metal precursor onto pre-supported nanoparticles of a second metal. XPS and other analytical data indicated that the preparation method provided fully alloyed bimetallic nanoparticles instead of core/shell structure. AgAu and AuCu bimetallic nanoparticles of various compositions with diameters ca. 3 nm, prepared in chloroform, exhibited characteristic XPS spectra of alloy structures [84]. [Pg.63]

An survey of recent developments in membrane processes, involving reverse osmosis (RO), ultrafiltration (UF), microfiltration (MF), electrodialysis (ED), dialysis (D), pervaporation (Pr), gas permeation (GP), and emulsion liquid membrane (ELM), has been provided by Sirkar (1997). [Pg.431]

Solidifiers, or gelling agents, solidify oil, requiring a large amount of agent to solidify oil— ranging from 16% to more than 200% by weight. Emulsion breakers prevent or reverse the formation of water-in-oil emulsions. [Pg.304]

M. L. Braden and S. J. Allenson. Reverse emulsion breaking method using amine containing polymers. Patent US 5032285, 1991. [Pg.362]

P. R. Hart. Method of breaking reverse emulsions in a crude oil desalting system. Patent CA 2126889,1995. [Pg.401]

Creaming Aggregation of lipid emulsion particles that then migrate to the surface of the emulsion that can be reversed with mild agitation. [Pg.1563]


See other pages where Emulsions reversible is mentioned: [Pg.100]    [Pg.100]    [Pg.506]    [Pg.2597]    [Pg.2666]    [Pg.212]    [Pg.452]    [Pg.452]    [Pg.163]    [Pg.489]    [Pg.470]    [Pg.470]    [Pg.471]    [Pg.472]    [Pg.487]    [Pg.487]    [Pg.502]    [Pg.200]    [Pg.836]    [Pg.1187]    [Pg.595]    [Pg.283]    [Pg.93]    [Pg.88]    [Pg.256]    [Pg.823]    [Pg.1495]    [Pg.76]    [Pg.34]    [Pg.226]   
See also in sourсe #XX -- [ Pg.377 ]




SEARCH



Emulsion reverse micelles

Emulsion reverse microemulsion

Reverse Micro-Emulsion Polymerization

Reverse emulsion

Reverse emulsion

Reverse emulsion technique

Reverse micelles, emulsion process

Reversible addition-fragmentation chain transfer emulsion polymerization

Reversible chain transfer in emulsion and miniemulsion

© 2024 chempedia.info