Influence of inorganic and organic electrolytes on the micellization of synthesized gamma-alkyl (C-12 and C-14) aspartate

Amino acid-based surfactants are emerging as important biocompatible and eco-friendly surfactants. This work explores C-12 and C-14 gamma-alkyl aspartic acid surfactants to understand their preparation, micellization, and surface properties, including critical micelle concentration (CMC), surface tension at CMC, thermodynamic properties, and biodegradation. A duration of 24 h produced the highest yield for the synthesis of gamma-alkyl aspartate from C-12 and C-14 fatty alcohols and aspartic acid. Their chemical structures were identified using elemental analysis, FT-IR, and H-1 and C-13-NMR. Synthesized sodium gamma-tetradecyl aspartate (SGTdA) possessed a lower CMC value than synthesized sodium gamma-dodecyl aspartate (SGDdA). However, a higher biodegradability was observed for the shorter-chain surfactant (SGDdA), that is, 84.6% in 7 days using activated sludge as a secondary effluent. In addition, the effect of inorganic and organic salts on the interfacial properties of surfactants was studied. It was observed that salts are very effective and active in reducing the CMC of surfactants.