It looks like it would take a velocity change of 1 km/s to make it work. For the mass you state, that would be a change of 1.4 * 10^16 joules of kinetic energy,

It looks like it would take a velocity change of 1 km/s to make it work. For the mass you state, that would be a change of 1.4 * 10^16 joules of kinetic energy, which is 3.2 megatons TNT equivalent. It would take a nuclear reactor to do it quickly enough. It looks like a 50 megawatt reactor would do the trick in about 10 years. That sounds practical. The tricky part is the propellant for the ion drive. The asteroid probably contains a lot of oxygen that could be extracted, but that takes fancy chemical processing, and the oxygen would tend to corrode the working parts. Shipping an inert gas from Earth would be technically easier, but the launch costs would be impossible unless you develop laser launchers first.