15. Can adding a certain amount of electrolytes such as salt or Yuanming powder into detergent improve the washing effect?
Answer Adding an electrolyte that is opposite to the surfactant ion into an anionic surfactant can generally increase the surface activity and reduce the critical micelle concentration (CMC). Increasing the counterion concentration of ionic surfactants affects the diffusion of the double electric layer of surfactant micelles, reduces the repulsion between surface active ions, and reduces the thickness of the double electric layer, thus making micelles easily formed and making The surface tension decreases and the CMC decreases. For example: in C12H25·OSO3Na solution, increase the NaCl concentration. For example, when adding 0.02mol/L concentration, you can Reduce the CMC from the original 0.0081mol/L to 0.0038mol/L. Add a concentration of 0.2mol/L and the CMC will drop to 0.00083mol/L. At the same time, add a small amount of salt (NaCl) to the liquid cleaning agent. The concentration of the cleaning agent can also be increased, but the amount should not be too much, otherwise precipitation will easily occur. Generally, about 1% NaCl can be added to liquid cleaning agents, and 20% to 40% Na2SO4 can be added to powdery cleaning agents. The electrolyte has little effect on non-ionic surfactants, but when the electrolyte is added to the solution, it can lower the cloud point of the non-ionic surfactant. This is the “salting out” effect of the electrolyte. The “salting out” effect The nonionic surfactant is aggregated into larger micelles, and a new phase is separated to a certain extent. If the cleaning agent is a mixture of anionic surfactant and nonionic surfactant, after adding NaCl On the one hand, the addition of anionic surfactant to nonionic surfactants can increase the cloud point; on the other hand, it can lower the cloud point. In this case, it is better not to add NaCl.
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