Systematic Study of Counterion Effects and NaCl-Induced Modulation of Foam Performance in Lauroyl Glutamate Surfactants

Abstract

This study systematically compares how three counterions (Na⁺, K⁺, NH₄⁺) regulate the interfacial properties, foaming behavior, and foam stability of lauroyl glutamate (LG) surfactants, and further examines how added NaCl modifies these properties in the sodium salt (SLG). The three counterions induce only slight variations in surface activity and foam generation. Their influence is more evident in foam stability, with the sodium salt exhibiting enhanced stability across a wider concentration range. For SLG, NaCl addition markedly lowers the critical micelle concentration and induces concentration-dependent changes in foaming behavior: 1% NaCl enhances foam generation, while higher salt levels diminish this effect. Foam stability is strongly affected in the sub-cmc regime, with 3% NaCl producing the most stable foams. Surfactant concentration and salt content are the main factors affecting foam performance.