Dalton, was reported to efficiently retain sugars, while H2SO4 (MW = 98 Dalton) can freely flow through NF membrane into the permeate side. After the split of sugars from acid, an evaporator is adopted to concentrate dilute acid to 50 ~ 70 wt.% . Jemaa et al. reported that this approach in this patent can recover > 82% acid, while the sugar stream can be concentrated as well; eventually, the little leftover sugars (~ 0.02 wt.%) in the recycled acid did not cause any sugar-related fouling issues during the evaporation . The demonstrated approach in this patent has a high acid recovery and the concentrated acid can be further utilized for hydrolysis, thus making it a practical and efficient method in the acid recycling and reuse.