What to use to remove Magnesium sulfate ( palm tree fertilizer) stain on the driveway
The best concrete cleaner I have found for stubborn stains is diluted muriatic acid. You can purchase it in diluted form at most hardware stores. I recently used it to remove dried tung oil from a concrete patio.
You need to be sure to wear gloves and protective goggles if applying it by hand. Follow directions on the bottle. In my case I left it on overnight covered with a plastic tarp. In your case you may not need to leave it on overnight. Be aware that you need to protect surrounding vegetation when applying it and rinsing it off.