My question is don't you set a restriction on the account that is eligible to receive loan from you?
If yes then you just have to ignore such users since you have already sets your restrictions
It is better to make a public thread about potential scammers and let them get tagged by more ppl so that other newbies dont fall for the same scam.
I believe you have your rules and regulations so if he or she doesn't meet your requirements then you or even violate the rules the best option is to formally put such user on the ignore list.
Putting such users on ignore list doesnt help anyone. Everyone should be constantly made aware to not deal with these type of users by actively monitoring their activity and warning others. The forum will be a much better place of we get more of such scambusters. I am usually on the side of ignoring spammers, not scammers.