Simultaneous Effects of Ionic Surfactant and Salt on Drop-Interface Coalescence

Document Type: Research note

Abstract

In this research, the effect ofmixed salts together with mixed ionic surfactants on dropinterface coalescence time was studied for the system of water (d) / toluene(c) as a model system. Sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) as anionic and cationic surfactants were used. Sodium chloride (NaCl) and magnesium sulfate were used as salts. In the first stage of experiments, the system of water and toluene was influenced separately with SDS+NaCl, SDS+MgSO4, CTAB+NaCl and CTAB+MgSO4. It was observed that drop size increased with SDS+NaCl and also with SDS+MgSO4. Partial coalescence times increased for all systems. Overall, this increase of coalescence time was more obvious when CTAB was applied. Also reduction in drop size was observed. In the case ofmixed surfactants with single salt, it was observed that partial coalescence was suppressed for the system with (SDS+CTAB)+MgSO4. On the other hand, drop size decreased and total coalescence time increased. This may be due to the difference between the anions and cations ofthe two salts. For the case ofmixed surfactants with mixed salts, drop size and coalescence time decreased.

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