Effect of Inorganic Additives on Solutions of Nonionic Surfactants IV: Krafft Points

doi:10.1002/jps.2600650707

Journal of Pharmaceutical Sciences

Volume 65, Issue 7, July 1976, Pages 979-981

https://doi.org/10.1002/jps.2600650707 Get rights and content

Abstract

Two polydisperse polyoxyethylated nonionic surfactants were found to possess Krafft points as well as cloud points. The significance of the Krafft point and the reason why it is rarely observed in nonionic surfactants are discussed. The values of the Krafft and cloud points of the two surfactants underwent only small changes as a function of surfactant concentration in the range of 0.5–7.5% (w/w). All electrolytes investigated, as well as urea, raised the Krafft points by between 1 and 4° in the concentration range of 0.5–4 molal. Included were salting‐in electrolytes, which raised the cloud points, as well as salting‐out electrolytes, which lowered them. Electrolytes that salt out nonionic surfactants strongly may depress the cloud point to the Krafft point temperature, rendering a water‐soluble surfactant insoluble in salt solutions at all temperatures.

REFERENCES (14)

H. Schott et al.
J. Pharm. Sci
(1975)
H. Schott
J. Pharm. Sci
(1969)
H. Schott
J. Colloid Interface Sci
(1973)
R.C. Murray et al.
Trans. Faraday Soc
(1935)
H.V. Tartar et al.
J. Amer. Chem. Soc
(1939)
N.K. Adam et al.
Trans. Faraday Soc
(1946)
D.G. Dervichian
Proc. Int. Congr. Surface Activity, 3rd
(1960)

There are more references available in the full text version of this article.

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Thus, if we can reversibly alter the KT of an ionic surfactant via an on-demand way, it is reasonably beneficial for people to recycle the high KT surfactant from the aqueous SESW effluents. Many strategies have been established for tuning the KT, such as tailoring the molecular structure [14–16] of surfactants, adding electrolytes [14,17–19] or other chemicals [11] and mixing different surfactants [20]. However, most of the above strategies can only monotonically regulate (decrease or increase) KT.
How to recycle surfactant and retrieve hydrophobic organic contaminants (HOCs) in the remediation of HOCs-polluted soil by means of surfactant-enhanced soil washing (SESW) is still a significant challenge. Here, a proof-of-concept strategy for solubilizing a model HOC of phenanthrene (Phe) in artificial Phe-polluted sand and co-pricipitating surfactant-Phe from the SESW effluent by reversible tuning Krafft temperature (K_T) of surfactant via CO₂/N₂-bubbling was reported for the first time. In the presence of N,N,N’,N’-tetramethyl-1,2-ethylenediamine (TEMDA), the K_T of sodium alkyl sulphonates (C_nAS, n = 12, 14 and 16) was reduced after CO₂-bubbling because of the formation of TEMDA carbonates; in contrast, the TEMDA carbonates could be deprotonated after the removal of CO₂ by N₂-bubbling, which enabled the K_T to increase, allowing subsequent precipitation of C_nAS. By alternating CO₂- and N₂-bubbling, the K_T of C_nAS-TEMDA could be reversibly switched over 10 cycles without causing obvious adverse distortions. The potential usage of this novel K_T-tuning strategy was demonstrated in a conceptual C₁₂AS-TEMDA-enhanced Phe-polluted sand washing. About 99.9% of Phe was solubilized by C₁₂AS at room temperature, about 92% of C₁₂AS and 99% of Phe could be co-precipitated, allowing both the total organic carbon and chemical oxygen demand of the residue wastewater were remarkably reduced to less than 25 mg L⁻¹ after a simple and conventional treatment with active carbon and ion-exchange resin. The precipitated C₁₂AS could be separated from Phe by a simple Soxhlet extraction.
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However, those with long alkyl chain (C16 and C18) and with a number of ethoxy groups higher than 7 exhibit both a cloud point and a Krafft point. Increasing the alkyl chain length increases the Krafft point as for ionic surfactants [15]. Nonionic surfactants are known to be much less sensitive to salt compared to anionic surfactants, nevertheless their solubility and cloud point are also influenced by the presence of anions and cations due to the changes in the water activity [16–20].
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Li et al. [61] have predicted CP of non-ionic surfactants including those having ethylene oxide groups with carboxyl groups as the hydrophilic part. For polyoxyethylene (10) cetyl alcohol (Brij 56) and polyoxyethylene (10) stearyl alcohol (Brij 76), the CP decreases in lower concentration range and then increases after passing through a minimum [62]. Similar type of decrease in CP for Brij 56 was observed by Ghosh and Moulik [63], although their values were higher than those obtained by Schott and Han [62] at the same weight%.
Phase separation in amphiphilic systems is an important phenomenon. The temperature at which an amphiphilic solution phase separates is known as Cloud Point (CP). This article reviews in detail the process of phase separation in various amphiphiles (surfactants, polymers and drugs) and effect of different classes of additives on the CP of these amphiphilic systems. Ions affect the CP of drugs in a different way: kosmotropes and hard bases decrease while chaotropes and soft bases increase the CP of nonionic and cationic surfactants. Anionic surfactants show CP in presence of quaternary salts only. Thus, depending upon the nature and concentration of additive, the CP of an amphiphilic system gets increased or decreased and, hence, properties of the system may be tuned as per the need and use. A system with CP at high concentration can be made to phase separate at lower concentration by simply introducing an appropriate additive in it. This makes the system cost effective. On the other hand, if not required, a low CP can be enhanced with the help of another type of a suitable additive.
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PAN, with a pi of 6.63,28 is formulated with 100 mM sodium chloride in a 83-mM sodium acetate buffer at pH 5.8.29 The CMC of PS80 is reported to be 14–15 mg/L in water,30 and this value is not expected to be affected by the presence of mAbs16 and only marginally lowered by salt.31–33 The terminology used in this article will be relative to the CMC of PS80 in water: ½xCMC (7 mg/L), 2xCMC (30 mg/L).
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Finally, any effects of the different electrolytes on the solubility of nitrogen (as opposed to the solubility of nonionic surfactants) in the agarose gels were considered to be inconsequential as concerns these bubble experiments; it had been found in earlier studies using agarose gels [49,139] that, for all moderate-sized decompressions as used here, bubble number was virtually independent of the absolute amount per se of dissolved gas in the surrounding medium. The results obtained from the outlined series of experiments supported the original (tentative) conclusion; it was found that the relative effectiveness of the different ions tested, in decreasing the degree of bubble formation in the aqueous gels (Table 2.2), exhibited many similarities with published data in the physicochemical literature [154–179] for salting out of identified nonionic surfactants. Briefly, the pronounced and very similar anion sequences obtained (using sodium and potassium salts), combined with earlier data, suggested that the polar portions of these nonionic surfactants represent either weak bases and/or amide groups [153].
Agarose gels make possible well-controlled, surface-chemical studies on microbubble stabilization and related bubble growth. The relative effectiveness of different added ions, in decreasing bubble formation within these aqueous gels, showed many similarities with published data in the physicochemical literature for salting out of identified nonionic surfactants. In particular, the cation sequences obtained, which indicated strong salting out in all cases, rendered it quite unlikely that ether linkages contribute to the hydrophilicity of the nonionic surfactants stabilizing gas microbubbles. It was concluded that the nonionic or hydrophobic surfactants stabilizing long-lived gas microbubbles are probably mostly, if not all, of natural origin.

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: Presented at the Division of Colloid and Surface Chemistry, American Chemical Society, Philadelphia meeting, April 1975. Adapted in part from a dissertation submitted by S. K. Han to Temple University in partial fulfillment of the Doctor of Philosophy degree requirements.

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Research ArticleEffect of Inorganic Additives on Solutions of Nonionic Surfactants IV: Krafft Points

Abstract

J. Pharm. Sci

J. Pharm. Sci

J. Colloid Interface Sci

Trans. Faraday Soc

J. Amer. Chem. Soc

Trans. Faraday Soc

Proc. Int. Congr. Surface Activity, 3rd

Research Article
Effect of Inorganic Additives on Solutions of Nonionic Surfactants IV: Krafft Points