Is it permissible to pay off interest accrued on a usurious loan with other usurious interest obtained from the same bank, in a country where only usurious banks exist, knowing that the borrower was unaware that his loan would accrue interest?

Usurious gains are illicit money and unlawful earnings that must be disposed of for charitable causes and public welfare. Whoever acquires any of it must get rid of it in such a way that they do not benefit from it by gaining an advantage or warding off harm, such as paying taxes, duties, or compulsory fees. The intention when disbursing it should be to rid oneself of unlawful money, not to give charity. Accordingly, it is not permissible for the questioner to use the usurious gains owed to her to pay off the usurious interest owed by her.