Is it permissible to take out a loan against one's salary and place the loan amount in a savings certificate to benefit from its returns, while committing to repaying the loan installments?

If the loan is repaid with a stipulated increase, then it is an usurious loan and forbidden. As for a goodly loan (qard hasan), there is no harm in it. Investing money in savings certificates in interest-based banks is forbidden, but if it is in Islamic banks that operate according to Sharia guidelines, then it is permissible.