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2022

Whether adding a certain amount of electrolyte (such as salt or sodium sulfate) to the detergent can improve the washing effect

The addition of electrolytes to anionic surfactants, which are opposite to surfactant ions, can generally improve the surface activity and reduce the critical micelle concentration (CMC). Because increasing the anti-ion concentration of ionic surfactants will affect the diffusion of the double electric layer of the surfactant micelles, reduce the repulsion between the surface active ions, and reduce the thickness of the double electric layer, thus making the micelles easy to form, reducing the surface tension and CMC. For example, in the Cl2H25.OSO3Na solution, increasing the concentration of NaCl, such as adding 0.02mol/L concentration, can reduce the CMC from the original 0.0081mol/L to 0.0038mol/L, adding 0.2mol/L concentration, CMC decreases to 0.00083mol/L, and adding a small amount of salt (NaCl) in the liquid detergent can also increase the concentration of the detergent, but the amount should not be too much, otherwise it is easy to produce precipitation. Generally, about 1% NaCI can be added to liquid detergent, and about 40% Na2S0420% can be added to powder detergent.
Electrolyte has little effect on non-ionic surfactants, but after adding electrolyte to the solution, the cloud point of non-ionic surfactants can be reduced, which is the "salting out" effect of electrolyte. The "salting out" action makes the non-ionic surfactant gather into larger micelles, and the new phase is separated to a certain extent. If the detergent is a mixture of anionic surfactant and non-ionic surfactant, after adding NaCI, on the one hand, the addition of anionic surfactant to the non-ionic surfactant can increase the cloud point; On the one hand, it can reduce the cloud point. In this case, it is better not to add NaCl.