After pledging your stocks you will receive the collateral margin in your account on T+1 day. You can then initiate an unpledge transaction to release these stocks for sale on T+1 day itself. Your unpledged will be available for selling on T+2 day

Let us understand this with an example

On Monday, you submit a request to pledge 100 shares of Company XYZ to receive collateral margin.

On Tuesday (one business day after your request), your account shall reflect the collateral margin you shall receive against those 100 shares. You can then initiate an unpledge transaction on T+1 day itself and your shares shall get unpledged on T+2 day i.e Wednesday.