Mechanism of Welan gum and silica nanoparticles on the foam properties and aggregation behavior of hydrocarbon and Gemini fluorocarbon surfactant dispersion

Nanoparticles and surfactant enhanced foams exhibit exceptional potential for the creation of environmental-friendly firefighting foams. In this work, we employ an ultrasonic disperser to fabricate a foam dispersion comprising Gemini surfactants, zwitterionic LAMC surfactants, nanosilica particles (NPs), and water-soluble polymer Welan. The enhancement mechanism of foam performance by NPs and Welan was investigated. The results show that the addition of 3% NPs and 0.07% Welan reduced surface tension by 14.56%, increased conductivity by 19.60%, and raised solution viscosity by 568.46%. Dynamic Light Scattering (DLS) and Cryogenic Transmission Electron Microscopy (Cryo-TEM) revealed that the inclusion of Welan transformed the micelles in the Gemini/LAMC solution from spherical to coacervates structures. The increase in viscosity was attributed to the formation of irregular coacervates when Welan and NPs were combined. Ross-Miles tests showed that the addition of NPs could increase foam volume by up to 12.91%, while the inclusion of Welan consistently reduced foam volume. Foam drainage and coarsening results demonstrated that the entanglement effect of Welan and the concentration blocking effect of NPs jointly enhanced foam stability. Incorporating 3% NPs creates an interconnected network that strengthens the foam structure and improves its stability. of 0.07% Welan gum. Within the experimental range, controlling the concentration ratio of NPs and Welan allowed for the simultaneous enhancement of foaming ability and stability of the firefighting foam. This study can provide theoretical guidance for application of NPs in firefighting foams.