Embedding hollow silica nanoparticles of varying shapes and dimensions in nanofiltration membranes for optimal performance

Spherical, cubic, or rodlike hollow silica nanoparticles were embedded in nanofiltration polyamide membranes. Each nanoparticle was separately added to an n-hexane solution of trimesoyl chloride, which was reacted with piperazine through interfacial polymerization. The modified membranes exhibited higher hydrophilicity. Field emission scanning electron microscopy depicted less aggregation in the case of the embedded spherical silica nanoparticles, on account of the smallest dimensions. Moreover, the corresponding modified membrane delivered the greatest water flux. The weight ratio of the spherical nanoparticles to trimesoyl chloride was established to be optimum at 0.5, at which the membrane yielded a pure water flux of 90 ± 3 L/m2 h (6 bar), and the rejection of different salts followed this trend: Na2SO4 (92%) > MgSO4 (70%) > MgCl2 (14%) > NaCl (11%). Therefore, the shape of hollow silica nanoparticles exerts an influence on the separation efficiency of the modified nanofiltration membranes.