BEHAVIOUR OF MICELLES OF A NON-IONIC SURFACTANT IN THE PRESENCE OF CONCENTRATED ELECTROLYTES AT DIFFERENT TEMPERATURES

Micelle formation of nonylphenol polypropylene polyethylene oxide (NPE-1800) was investigated in aqueous and aqueous electrolyte solutions. The study focused on the effect of temperatures, 25, 30, 35 and 40°C and on the effect of concentrated inorganic electrolytes, NaNO₃, KCI, KNO₃, K₂SO₄ and MgCl₂.6H₂O. The Critical Micelle Concentration (CMC) was determined by surface tension measurements. On the basis of the actual CMC and its temperature dependence, the thermodynamic functions of micelle formation (δH°, δS°, δG°) were calculated.

According to the experimental results, the CMC at high electrolyte concentration increases with increasing temperature. This behaviour is attributed to the salting-in mechanism.

Viscometry supports the behaviour of NPE-1800 in concentrated electrolytes and the decrease of (η is attributed to the decrease of the solvency of the electrolytic solution.