Cleaning concrete to prep for staining

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I want to stain the concrete in my entryway, but there is old adhesive and paint on there. I have tried paint thinner, lacquer thinner, acetone, muriatic acid, another adhesive remover from Home Depot, and even a floor sander. It is coming off, but very very slowly. I have already spent many hours and the space is only 50 square feet. The sanding worked the best, but not up against the wall. Does anyone have a suggestion for getting the concrete nice and clean enough for stain?
Thank you!