I looked through the spells and details of the PRD and can't find any way to do this in RAW. Maybe some advice on coming up with a homebrew spell or combination of abilities or spells could be forthcoming? My players will be soon encountering a mad warrior with a fearsome sword that is anarchic, in a world where this property would be considered a 'curse' and a taint on the blade. This blade was stolen from a fallen warrior of a great clan and corrupted by evil beings. They might want it back but only if it could be cleansed of its taint. Might work as a possible side quest.
As far as rules designed for doing just his, i'm not sure that any exist. This isn't that large of a deal as it sounds as if you are the GM. GM fortunately have the ultimate say when it comes to what is or isn't possible in their games, regardless of preestablished rules, so it would be just as easy to name of any sort of ritual etc to do so.
Now i know this doesn't sound like it helps a whole lot, but never fear. I do have an alternative option if you wish to see it out as rules tight as possible. A creature in both the bestiary 3, and misfit monsters redeemed, aptly named, the Disenchanter has an ability to "drink" the enchantment from magical items, rendering them mundane.
Finding one being a perfect sidequest-esque scenario, in my opinion.