Electrolytes, precipitation surfactants

Other CTAs and inhibitors also tried (about 0.05 M) were anionic mer-captoacetate and mercaptosuccinate and cationic isopropylamine, 1-dimeth-ylamino-2-propanol, cysteamine hydrochloride, and copper sulfate. The pH was adjusted as necessary to yield the desired ions. None of the ionic CTAs reduced the measured PLMA MW, although mercaptoacetic acid at a pH of 2.2 (mixed anionic and neutral species) reduced the molecular weight almost to that obtained with mercaptoethanol. The ionic CTAs may increase the micelle aggregation number (electrolyte effect). Cu(II) precipitated surfactant, but the other solutions were clear. 

Identical correlations have been observed for albite [372], confirming the validity of the two- and three-dimensional precipitation models in interpreting the mechanism of adsorption of weak-electrolyte-type surfactants on silicates. However, the concentration at which two-dimensional precipitation for albite... 

Uses Shampoo surfactant, detergent, conditioner Properties Golden moderately vise, liq. faintly spicy odor sol. in water, in polar solv. with some electrolyte precipitation vise. 25004500 cps doud pt. 50 F cl. pt. 50-55 F 36% solids Supro-Tein R [Tri-K Ind.]... 

The carrier fluid was deionized water containing 1 gm/l of Aerosol OT and 1 g/l sodiiom nitrate. Compared to the use of potassium nitrate as electrolyte, suggested by Coll et al. (lO), the carrier solvent used in this investigation has much better clarity and at room temperature has no tendency to precipitate the surfactant. ... 

The electrolyte effect for the adsorption of anionic surfactants which leads to an enhancement of soil removal is valid only for low water hardness, i.e. low concentrations of calcium ions. High concentrations of calcium ions can lead to a precipitation of calcium surfactant salts and reduce the concentration of active molecules. Therefore, for many anionic surfactants the washing performance decreases with lower temperatures in the presence of calcium ions. This effect can be compensated by the addition of complexing agents or ion exchangers. 

In the case of non—eutectic systems, the solid phase shows nearly ideal mixing, so that the surfactant components distribute themselves between the micelle and the solid in about the same relative proportions (i.e., both the mixed micelle and mixed solid are approximately ideal). However, in the case of the eutectic type system, the crystal is extremely non-ideal (almost a single component), while the micelle has nearly ideal mixing. As seen in earlier calculations for ideal systems, even though the total surfactant monomer concentration is intermediate between that of the pure components, the monomer concentration of an individual component decreases as its total proportion in solution decreases. As the proportion of surfactant A decreases in solution (proportion of surfactant B increases) from pure A, there is a lower monomer concentration of A. Therefore, it requires a lower temperature or a higher added electrolyte level to precipitate it. At some... 

Studies of surfactant precipitation have concentrated on predicting the precipitation phase boundaries (i.e., the amount of added electrolyte necessary to cause... 

Previous work has shown that binary surfactant systems containing Dowfax 8390 and the branched hydrophobic surfactant AOT can form Winsor III systems with both PCE and decane whereas DOWFAX 8390 by itself cannot (Wu et. al. 1999). This binary surfactant system was used in conjunction with hydrophobic octanoic acid to help with phase behavior and lessen the required concentration of CaCl2. Since this formulation is rather complicated, questions about field robustness arise. Thus, for the phase behavior studies presented here, we used the simple binary system of the nonionic TWEEN 80 and the branched hydrophobic AOT, and we optimized the NaCl concentration to give the Winsor Type III system. The lesser electrolyte concentration requirement for the binary TWEEN 80/ AOT system helps to decrease the potential for undesirable phase behavior such as surfactant precipitation, thereby increasing surfactant system robustness. 

Generally speaking, for a stable emulsion a densely packed surfactant film is necessary at the interfaces of the water and the oil phase in order to reduce the interfacial tension to a minimum. To this end, the solubility of the surfactant must not be too high in both phases since, if it is increased, the interfacial activity is reduced and the stability of an emulsion breaks down. This process either can be undesirable or can be used specifically to separate an emulsion. The removal of surfactant from the interface can, for example, be achieved by raising the temperature. By this measure, the water solubility of ionic surfactants is increased, the water solubility of non-ionic emulsifiers is decreased whereas its solubility in oil increases. Thus, the packing density of the interfacial film is changed and this can result in a destabilisation of the emulsion. The same effect can happen in the presence of electrolyte which decreases the water solubility mainly of ionic surfactants due to the compression of the electric double layer the emulsion is salted out. Also, other processes can remove surfactant from the water-oil interface - for instance a precipitation of anionic surfactant by cationic surfactant or condensing counterions. 

In the solvent method the separation of the solubilised or dispersed material from the solvent phase can be explained by precipitation or phase change induced by solvent evaporation, addition of electrolyte, pH modification or heat treatment (Krochta and McHugh 1997). Such treatments can be adjusted to enhance film formation or specific properties. For composite emulsion-based films or coatings a lipid material and most likely a surfactant, is added to the solution, which is then heated above the lipid melting point and homogenised. The prepared solution is then applied on an appropriate support and the solvent evaporates. 

Gelatin will also react with aldehydes and aldehydic sugars, anionic and cationic polymers, electrolytes, metal ions, plasticizers, preservatives, and surfactants. It is precipitated by alcohols, chloroform, ether, mercury salts, and tannic acid. Gels can be liquefied by bacteria unless preserved. 

The advantages of the electrochemical pathway are that contamination with byproducts resulting from chemical reduction agents are avoided and that the products are easily isolated from the precipitate. The electrochemical preparation also provides a size-selective particle formation. Reetz et al. have conducted several experiments using a commercially available Pd sheet as the sacrificial anode and the surfactant as the electrolyte and stabilizer. Analysis of the (C8Hi7)4N Br-stabilized Pd ° particles produced have indicated that the particle size depends on such... 

An increase in the ionic strength of the aqueous phase due to addition of electrolyte (O.IM NaBr) causes an increase in the effectiveness of adsorption of DTAB onto precipitated silica (Fig. 11 a). The micellization in the bulk phase is thermodynamically favoured and the cmc is reduced. The effects are presumably due to the decreased repulsion between the ionic heads of the surfactant and to the salting out of the monomers by electrolyte. Since the effective size of the hydrophilic group is smaller at higher ionic strength, the effectiveness of adsorption becomes greater as a result of closer packing of the surfactant... 

Salinity Salinity plays at least two important roles, namely it maintains the integrity of the reservoir and it balances the physicochemical environment so that surfactant formulation stays close to optimal. Thus, ultra-low interfacial tension and oil solubilisation are very sensitive to salinity. Mixing of the surfactant slug with connate water may alter the surfactant formulation mainly due to dilution and to the incorporation of new electrolytes to the formula. Adsorption and desorption of electrolytes, particularly divalent cations, onto or from solid materials such as clay, will also change the salinity of the aqueous phases to some extent and may cause surfactant precipitation, which is however not always an adverse effect [151]. In order to attenuate the undesirable salinity effects on formulation, surfactants able to tolerate salinity changes [109], high salinity [150] and the presence of divalent ions [112] maybe used. 

An increase in electrolyte concentration reduces the solubility of anionic surfactants in the aqueous phase and increases their tendency to accumulate at the solid—liquid interface. An increase in temperature offsets the loss in solubility to some degree For the DPES—AOS on Berea sandstone, the slopes of the lines in Figure 13a decrease as the temperature increases, and this finding lends support to the hypothesis that surfactant adsorption is related to surfactant solubility. Adsorption of surfactants that are less salt-tolerant than the DPES—AOS, such as the AOS and the IOS, increases much more steeply with salinity. Both surfactants adsorb negligibly at salinities of 0.5 mass % NaCl, but adsorb similarly to the DPES—AOS at a salinity of 2.3 mass %. At moderate salinities (on the order of 3 mass %), these surfactants precipitate, which severely limits their applicability to foam-flooding in many reservoirs that are currently being flooded with hydrocarbon solvents. 

At or in the proximity of their pi values proteins exhibit a minimum total charge and reduced solubility in the electrolyte solution [350,370,385]. This increases the probability of aggregation, and is further enhanced by the low ionic strength of the ampholyte buffer. Under these conditions protein precipitation results from hydrophobic interactions. These interactions can be suppressed by addition of additives such as ethylene glycol (10-40 %), non-ionic or zwitterionic surfactants (1-4 %), or sorbitol to the ampholyte buffer. 

Some hydrophobic cations, such as tetrabutyl ammonium, appear to have the opposite action on the CMC. OH acts as normal anion whereas practically has no effect up to ca 0.5 M and it rise the CMC at higher concentrations in view of the ether oxygen protonation of the ethylene oxide chain. As a result of electrolyte addition, strong specific binding of ions may make surfactants sometimes more soluble and, in contrast, it may cause coacervation. Surfactant precipitation or strong aggregation occurs in many cases. 

As seen in Figure 7.6 (a-d), the interconnections in coalescence pores are different compared with those of the primary pores. In order to have primary pore structure in the presence of additives/fillers, the concentration of the additives must be low. The example below illustrates one such case. In this example, the aqueous phase contains 0.5 wt.% hydroxyapatite dissolved in 15% phosphoric acid solution. After emulsification and polymerization, PHP is soaked in 1 M NaOH to precipitate hydroxyapatite and subsequently washed in water to obtain pH = 7. These materials are then washed in isopropanol to remove residual surfactant, toxic monomer residues, and electrolytes. Polymer samples were finally dried in a vacuum oven and then sterilized in an autoclave before use as support in micro-bioreactors or tissue culture studies. 

The influence of electrolytes divides into two areas, the influence on nonionic (uncharged) surfactants and that on ionic materials. For nonionic surfactants the effects are either salting out or salting in , in line with observations from the Hofmeister series of electrolyte effects on protein precipitation. Whilst there has been much discus-... 

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