The Effect of Halide Counter Ions and Methanol on the Foaming Behavior of Cationic Surfactants and a Mechanism Study

In this work, four quaternary ammonium cationic surfactants including cetyltrimethyl ammonium fluoride (CTAF), cetyltrimethyl ammonium chloride (CTAC), cetyltrimethyl ammonium bromide (CTAB) and cetyltrimethyl ammonium iodide (CTAI) were investigated to study the effect of halide anions on the surface activity and foaming performance. The result showed that CTAF had superior surface activity, which could reduce the surface tension of water to 33i5 mN/m at a low CMC (critical micelle formation concentration) of 1.65 mmol/L. Based on the calculation of A(min )(the minimum occupied area per surfactant molecule), we assumed that this higher surface activity was related to the small ionic radius of the fluorine ion (F-). The foamability and foam stability of CTAF has great advantages over other surfactants studied. On this basis, the factors affecting the formation and stabilization of the CTAF foam were investigated. The results showed that foam formation benefited from high temperatures and low methanol concentration, while high salinity was beneficial for foam stability. When CTAF at a concentration of 0.2% was used as a foaming agent, foaming was excellent at a methanol concentration of 10%, a salinity of 22 x 10(4) mg/L, and a temperature of 90'C. With this study, uncertainties that existed in the literature regarding the effect of anion on surface activity and foam performance were explained and the effect of temperature, methanol and salinity on foam generation and stabilization was understood.