Destroying individual ants is of no use, as the colony will continue as long as the queen is alive. Eventually they will die back normally when they swarm. Most proprietary ant killers should work as they operate on the principle that the worker ants take the poison back into the colony. Perhaps you are being too impatient for the poison to work?
At the end of the day, as you can rake the ant hills out, and they do no harm other than appear unsightly, is it necessary to destroy them?

Thank you but I am finding that these piles are destroying the lawn - it is dying.Also they are now in the border, and
plants are dying off, when I pull them out there is again
masses of ants un derneath