A method of generating a refined sugar stream that comprises xylose from a biomass hydrolysis solution, including contacting a biomass hydrolysis solution that includes a population of mixed sugars comprising xylose, an acid, and impurities, with a thermally-phase separable solvent such as a glycol solvent to form an extraction mixture; and separating from said extraction mixture a first stream including the thermally-phase separable solvent, acid, and impurities and a second, refined sugar stream that comprises xylose. The thermally-phase separable solvent is an ethylene glycol or a propylene glycol ether, such as 2-butoxyethanol or 1-propoxy-propanol or any combination thereof.