  The accretion disk that forms after a neutron star merger is a source of
neutron-rich ejecta. The ejected material contributes to a
radioactively-powered electromagnetic transient, with properties that depend
sensitively on the composition of the outflow. Here we investigate how the spin
of the black hole remnant influences mass ejection on the thermal and viscous
timescales. We carry out two-dimensional, time-dependent hydrodynamic
simulations of merger remnant accretion disks including viscous angular
momentum transport and approximate neutrino self-irradiation. The gravity of
the spinning black hole is included via a pseudo-Newtonian potential. We find
that a disk around a spinning black hole ejects more mass, up to a factor of
several, relative to the non-spinning case. The enhanced mass loss is due to
energy release by accretion occurring deeper in the gravitational potential,
raising the disk temperature and hence the rate of viscous heating in regions
where neutrino cooling is ineffective. The mean electron fraction of the
outflow increases moderately with BH spin due to a highly-irradiated (though
not neutrino-driven) wind component. While the bulk of the ejecta is still very
neutron-rich, thus generating heavy r-process elements, the leading edge of the
wind contains a small amount of Lanthanide-free material. This component can
give rise to a ~1 day blue optical `bump' in a kilonova light curve, even in
the case of prompt BH formation, which may facilitate its detection.
