  We consider a mixture of active and passive run-and-tumble disks in an
inhomogeneous environment where only half of the sample contains quenched
disorder or pinning. The disks are initialized in a fully mixed state of
uniform density. We identify several distinct dynamical phases as a function of
motor force and pinning density. At high pinning densities and high motor
forces, there is a two step process initiated by a rapid accumulation of both
active and passive disks in the pinned region, which produces a large density
gradient in the system. This is followed by a slower species phase separation
process where the inactive disks are shepherded by the active disks into the
pin-free region, forming a non-clustered fluid and producing a more uniform
density with species phase separation. For higher pinning densities and low
motor forces, the dynamics becomes very slow and the system maintains a strong
density gradient. For weaker pinning and large motor forces, a floating
clustered state appears and the time averaged density of the system is uniform.
We illustrate the appearance of these phases in a dynamic phase diagram.
