Foams stabilization by silica nanoparticle with cationic and anionic surfactants in column flotation: Effects of particle size

Abstract Foams have been widely used in flotation, but they stabilized solely by surfactants was unstable. Nanoparticles (NPs) can improve the performance of aqueous foams. It is interesting to evaluate and understand the effect of NPs on foam property in column flotation. In this paper, silica nanoparticles (SNPs) with three different sizes (20, 100 and 500 nm) were chosen as model NPs; the performance of foams stabilized by SNPs and two surfactant, cetyltrimethylammonium bromide (CTAB) and anionic sodium dodecylsulfate (SDS), were investigated experimentally. For CTAB/SNPs dispersion, although the foamability was lower, SNPs obviously improved static foam stability. Moreover, smaller SNP exhibited a more effective improvement for foam stability because of its low adhesion energy and high number concentration. For SDS/SNPs dispersion, even if SNPs were hydrophilic, the foam stability was still enhanced since these particles induced congestion in the node and slowed down drainage. Larger SNP had a greater ability to delay the liquid drainage and enhance the foam stability. Besides, CTAB/SNPs and SDS/SNPs foams also maintained their dynamic stability through weakening the foam drainage. These results provided theoretical supports for the usage of NPs in practical application such as flotation.