Influence of Inorganic Salts and pH on Surface Activity of Biodegradable Amido Gemini Amine Oxide Surfactant.

The present study was designed to provide information regarding the influences of pH and inorganic salts on the surface activity of the amido Gemini amine oxide surfactants, the formula of which was CnH2n+1CONH(CH2)2N+O-(CH3)-(CH2)2-(CH3)N+O-(CH2)2NHCOCnH2n+1 (n=11, 13, 15, and 17). Their biodegradability was also investigated. The results showed that the critical micelle concentration (CMC) and the corresponding surface tension (γCMC) changed regularly with the increase of the mass concentration of NaCl and CaCl2. The optimal CMC and γCMC can be obtained by adjusting the inorganic salt content. Besides, the CMC near the isoelectric point of the surfactant is higher than the CMC within the isoelectric point. Furthermore, the biodegradability test revealed that the prepared surfactants had good biodegradability which was above 96% after 7 days.