Precipitation of surfactant

Sequestration forms the basis for detergent and water-treatment appHcations of polyphosphates. Sequestration of hardness ions by sodium tripolyphosphate used in detergent formulations prevents the precipitation of surfactants by the hardness ions. Sodium polyphosphate glass (SHMP) may be added to water system to prevent the formation of calcium or magnesium scales by reducing the activity of the hardness ions. However, if the ratio of cation to polyphosphate is too high at a given pH, insoluble precipitates such as may result instead of the soluble polyphosphate complexes. The... 

Chromatographic separation of the components is minimal under laboratory conditions and it is possible that this can be extrapolated to actual Field conditions. Even if separation were to occur, the AOS would be depleted first. The surfactant solution would then always be richer in DPOS which prevents precipitation of surfactant within the reservoir. 

To evaluate the importance of multivalent cation precipitation of surfactants by multivalent cations present in the formation brine or resulting from cation exchange and dissolution of minerals such as limestone, dolomite, etc., a very limited study of the calcium tolerance of selected alkylbenzene sulfonates was undertaken. 

Significance For Equilibrium Adsorption Measurements. While these results appear to have little relevance for micellar slugs, they are quite relevant for equilibrium adsorption measurements. They show that precipitation of surfactants can be expected to occur if the calcium ion concentration exceeds the limit required to initiate precipitation (SDBS 200 ppm and TRS 10-410 < 10 ppm). Unless the adsorbent is strongly colored and the surfactant concentration is substantial, i.e., > 0.1 wt.%, one may experience difficulty in detecting the presence of precipitated surfactant. 

Shampoo formulations generally contain sodium and combinations of ammonium lauryl/ laureth sulfates to overcome and improve any issues of solubility and precipitation. By using the combinations, increased steric hindrance and lower ionization level of the ammonium group help prevent precipitation in the presence of conditioning agents in a 2-in-l-type formulation and precipitation of surfactants due to the common ion effect if many sodium ions are otherwise present in the formulation. " ... 

Castro, S. H., Vurdela, R. M., and Laskowski, J. S. 1986. The surface association and precipitation of surfactant species in alkaline dodecylamine hydrochloride solutions. Colloids Surf. 21 87. 

Endo-exo ratios of the micelle-catalysed reactions have been determined by adding 0.25 mmol of 5.1c and 0.5 mmol of 5.2 to a solution of 5 mmol of surfactant and 0.005 mmol of EDTA in 50 ml of water in carefully sealed 50 ml flasks. The solutions were stirred for 7 days at 26 C and subsequently freeze-dried. The SDS and CTAB containing reaction mixtures were stirred with 100 ml of ether. Filtration and evaporation of the ether afforded the crude product mixtures. Extraction of the Diels-Alder adducts from the freeze-dried reaction mixture containing C12E7 was performed by stirring with 50 ml of pentane. Cooling the solution to -18 C resulted in precipitation of the surfactant. Filtration and evaporation of the solvent afforded the adduct mixture. Endo-exo ratios... 

In the removal of contaminating ions such as (PO or Fe " a precipitate such as Ca2(P0 2 Fe(OH)2, after oxidizing ferrous ion to ferric, is formed and the soHd is removed. The addition of surfactants is usually not essential (nor desirable) since most waters contain natural surfactants that would render the soflds sufficiently hydrophobic for flotation to occur. Such surfactants derive from the degradation of organic matter, and humic substances abundantly available in nature (30). 

The resulting solutions contain high dissolved soHds content in the range of 30 wt % or more. Special surfactant technology (25) is sometimes used to avoid precipitation of Al(OH)3 or at least to extend the shelf life of the caustic Hquor. 

The Krafft point has practical implications for the solubility of surfactants. Only above the Krafft temperature can concentrated surfactant solutions be prepared. Otherwise, on cooling a hot surfactant solution a sudden precipitation may occur. A linear correlation between the Krafft temperature TK (°C) and the carbon number nc of sodium alkanesulfonates C10-C22 is given by the following equation ... 

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. ... 

From the characteristics of the methods, it would appear that FD-MS can profitably be applied to poly-mer/additive dissolutions (without precipitation of the polymer or separation of the additive components). The FD approach was considered to be too difficult and fraught with inherent complications to be of routine use in the characterisation of anionic surfactants. The technique does, however, have a niche application in the area of nonpolar compound classes such as hydrocarbons and lubricants, compounds which are difficult to study using other mass-spectrometry ionisation techniques. 

The use of polyethylene glycol ethers in a process in which a high viscosity emulsion is formed on contact with residual crude oil has also been tested as a means of plugging thief zones using surfactants (248-250). Precipitation of sodium pectate when fresh water solutions contact brine has been proposed as a method of plugging high permeability zones (251). 

EXPERIMENTAL PROCEDURES AUTOMATED TURBIDIMETRIC TITRATION. A method for the automated aqueous turbidimetric titration of surfactants has been published (10) in which anionic surfactants are titrated against N-cetylpyridinium chloride to form a colloidal precipitate near the equivalence point. N-cetylpyridinium halides have a disadvantage in that they have the tendency to crystallise out of solution (15), consequently the strength of the solution may alter slightly without the knowledge of the operator, also the crystals suspended in solution may cause damage to the autotitrator. In view of these drawbacks hyamine was preferred as the titrant. 

The proposed mechanism of effect of surfactant and ultrasound is reported in Fig. 7.5. The long chain surfactant molecules attach to surface of nanoparticles due to physical adsorption. Only thin layer is adsorbed onto the CaC03 nanoparticles. Due to presence of ultrasound and use of surfactant will control the nucleation. Surfactant keeps the particles away from each other by preventing flocculation due to change in surface tension of reaction mass. The concentration of additives was changed from 0.2 to 1.0 g/L. Addition of 0.2 g/L tripolyphosphate shows the increase in the rate of precipitation which is determined from the Ca(OH)2 consumption. Polyacrylic acid shows the least rate of precipitation (0.115 mol/1), which... 

The ability of chitosan to form complexes is of particular interest. Being slightly basic, it will readily form complexes with anionic compounds. Initially it forms into micelles with small amounts of anionic surfactants, leading to precipitation of a complex as the concentration of the anionic surfactant increases. Chitosan will complex with anionic... 

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. 

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