Surfactant formulations salt tolerance

In spite of the good calcium and magnesium tolerance of AOS systems, situations can arise whereby too many exchangeable hardness ions present themselves to the surfactant formulation. One way to overcome this is by blending AOS with a divalent cation-tolerant surfactant. A product which has been field-tested [87] is a blend of AOS and a disulfonated alkyldiphenyloxide (DPOS). Calcium and magnesium salts of DPOS are water-soluble and remain soluble even in solutions which are very concentrated in calcium and magnesium salts. 

Ionic surfactants are sensitive to water hardness whereas polyethoxylated surfactant are not. Hence the mixing of both types often result in formulations that are salt tolerant for applications such as detergency or enhanced oil recovery. 

Salinity Tolerance. As the petroleum reservoir salinity can be very high, the surfactant formulations should be designed for high salt tolerance. The widely used petroleum sulfonates for enhanced oil recovery exhibit relatively low salt tolerance in the range 2-2.5% NaCl concentration, and even smaller for the optimal salinity. The presence of divalent cations in the brine decreases the optimal salinity of surfactant formulations (44). 

Bansal, V.K. and Shah, D.O., The Effect of Ethoxylated Sulfonates on Salt Tolerance and Optimal Salinity of Surfactant Formulations for Tertiary Oil Recovery.,... 

Alkyl ether sulphates are used relatively little in laundry products, especially in solid ones. The surfactant has a very poor solid form, the pure product being amorphous, somewhat hygroscopic and sticky. Commercial dry ether sulphates are unknown other than as blends of 50% with carrier solids, such as sodium carbonate. In liquid formulations, 3-mol ether sulphates can be used to give improved solubility and hard water tolerance in unbuilt liquids and amine salts are occasionally used. 

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