Performance Study of a <scp> SiO ₂ </scp> / <scp>SDS</scp> Composite Foam System

ABSTRACT To improve foam dust suppression efficiency in underground coal mines, this study proposes a SiO 2 /sodium dodecyl sulfate (SDS) composite foam system. Hydrophilic nano‐SiO 2 and anionic surfactant SDS are taken as research objects, and the influences of particle size and concentration on foam performance are studied via wetting, foaming and flowability tests. Results indicate that larger particles cause severe agglomeration, reducing foaming volume and extending coal dust settling time. Higher particle size and concentration weaken solution flowability because stronger interparticle interactions limit liquid flow. The critical micelle concentration (CMC) of SDS solution is about 0.7 wt%, corresponding to the best foaming capacity. SDS molecules adsorb on nano‐SiO 2 to achieve in situ hydrophobic modification. Modified particles attach to the gas–liquid interface, restrain bubble coalescence and prolong foam half‐life by slowing film drainage, boosting film strength and building steric barriers. Nano‐SiO 2 barely changes surface tension, and SDS dominates surface properties after reaching CMC. Analytic hierarchy process (AHP) evaluation confirms the optimal formula: 10 nm SiO 2 with a concentration of 0.2%.