Can I legally evict my daughter(22) and son (21) they live rent free in my home while their mother and myself live elsewhere pending a divorce

Yes you can but you have to go by the state law of the state your house that your kids are living in.
The law should go something like a written eviction notice that they have to leave within xx days. Then after that if they are still there you have to get a court eviction for the same amount of days. Then after that the sheriff/constable escorts them off the property if they still have not left.

You can follow though with legal eviction following your local laws. Normally notice, and if they don't move you go though the court that handles evictionz

As was said, certainly you can, but do consider the emotional and familial ramifications if you know it will cause a major issue.

Obviously don't know the situation, but just in case, be sure it is not something you are considering out of spite or anger due to the divorce.