Raw halloysite nanotubes (HNTs) have been dispersed and cut by ultrasonic scission.
Short HNTs have been purified by two-step uniform viscosity centrifugation.
Length controllable HNTs can be prepared by changing ultrasonic time or power.
The purified HNTs are homogeneous with much less impurities.
The separation method can be used to separate chemically synthesized nanotubes.