What sort of mass loading?

The dust grains are micron-sized, which is about 1e-15 kg apiece. At 36/mm3, that gives a density of about 36 mg/m3.
Since the volume (and mass) go as r3, while area goes as r2, the mass loading is r dependent ~ 25 mg * r. A 200 meter radius dusty plasma sail would then have the mass-loading of a carbon fiber sail.
Can we make the dust lighter and more reflective? Perhaps buckeyballs with chelated sodium atoms. Or even reflective ions - e.g., transition metal ions.

The dust grains are micron-sized, which is about 1e-15 kg apiece. At 36/mm3, that gives a density of about 36 mg/m3.