Separation of Nanoporous Silica Particles

Abstract: In this study a sample of particles in a size region of 0.05-10 μm were run through a centrifugation process with the ambition to make it monodisperse. The product requirements were stated as follows, particles within the size range of 2 to 3.8 μm should be isolated and separated from the sample with a D90/D10 < 1.4 where the D90/D50/D10 values should be approximately 3.8 μm/2.5 μm/2 μm. It was found that two layers of sucrose with a 50/50 volume distribution of 45w% sucrose solution and 60w% sucrose solution respectively, was the most efficient density gradient arrangement for separation of this particular sample. The optimal time and RPM combination was found to be 5 min 3000 RPM with a fast acceleration and slower deceleration, ratio 9:6. Two centrifugation rounds on the same sample improved D90/D10 drastically. The effect of centrifugation rounds on D90/D10 was not investigated further than 3 rounds, however this would be a good starting point for further studies. The upscaled test runs indicated a positive result, i.e. the yields with respect to both mass and purity were reproducible. It is worth mentioning that the upscale was only in the volume, sample load volume and surface area factors. The gradient height or particle travel distance remained the same.