What do you mean with purification?

Centrifuge RPM will depend on the material type (density) and size of the particles.

Large particles can be sedimented from a solution on a bench top centrifuge whereas small particles can be sedimented from a solution using an ultracentrifuge.

When a highly polydisperse sample is centrifuged, large particles will sediment at low speeds and small particles will sediment at high speeds.

As the radius of the rotor increases, centrifugal force increases. A particle of same size, when centrifuged under similar conditions with just the radius of rotor differing, then the particle will

experience higher centrifugal field in a rotor with a larger diameter.

to sediment large particles @Simone Belluco