What is the ruling on disposing of lawful money that was deposited in a Riba-based bank and became mixed with Riba, and is it permissible to deposit it in an Islamic bank?

The deposited money is lawful. If it comes with usurious interest, then this interest must be disposed of by spending it on the welfare of Muslims and the poor. The account must be closed, and no further deposits should be made as long as an Islamic bank is available. Whoever wishes to deposit money should deposit it in an Islamic bank account.