Exploring the effects of interactions between nonylphenol ethoxylate and ionic surfactants on interfacial and foaming properties

Abstract

Nonylphenol ethoxylate (NPE-9) is a widely recognized non-ionic surfactant that finds extensive applications in various industries, including detergency, emulsification, and agriculture. Combining NPE-9 with an ionic surfactant reflects an inexpensive and highly promising approach for enhancing the efficacy of NPE-9. This study explores the molecular interactions between NPE-9 and ionic surfactants (SDS and CTAB) and examines the impact of these interactions on interfacial properties and foaming. The micellization parameters, including the critical micelle concentration (CMC), degree of counterion binding (β), degree of counterion dissociation (α), and change in free energy of micellization (ΔGmic), were investigated for sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) in the presence and absence of NPE-9, using conductometric measurements. The combined effect of NPE-9 and an ionic surfactant resulted in a synergistic interaction, reducing the CMC of the ionic surfactant, and promoting the formation of micelles. The interaction between NPE-9 and ionic surfactants at the air/water interface was investigated using surface tension measurements. The interfacial properties improved through the competitive adsorption and synergistic effect observed between NPE-9 and an ionic surfactant. In this context, the surface tension data of NPE-9 is utilized to calculate interfacial parameters, including maximum surface excess concentration (Γmax), minimum area per molecule (Amin), and surface effectiveness (π). Adding SDS and CTAB to NPE-9 solutions resulted in a notable enhancement in foamability and foam stability. The utilization of various techniques consistently produced improvements in the interfacial and foaming properties of NPE-9.