Say no you can't. It is not your responsibility if he uses the money for non-halal purposes (since he didn't say and you don't know for sure, otherwise if you do, you MUST deny him), but if you don't know what he's using it for and suspect he doesn't care about non-halal loan, then you don't know him that well. I don't think you should lend an amount so large to someone you don't know that well. He might either reneg on the debt and leave you in disappointment and frustration, or will be a burden on him to repay to you and be under pressure for a long time till he does. Debts need to manageable, and that seems too much money for someone you're not that close to and/or you don't know that well.
Personal opinion only of course.