They use such things where I work, to remove static from paper as its being procesed.
Negative and positive ions are sprayed over paper using a linear array of needles.
The usual way to make ions from dc is to use a step up switching supply followed by a cockroft walton multiplier, if I got it right its a case of reversing the phase of the trandformer secondary, reversing the rectifier or catch diode and then reversing all the diodes in the cockroft walton to get positive rather than negative ions.