Acid recovery by electrodialysis and its economic implications for concentrated acid hydrolysis of wood

Satisfactory separation of either hydrochloric or sulfuric acid from sugars in wood hydrolyzates by application of membrane technology is technically feasible. The permeability of disaccharides is less than 1% that of the acids. Acid flux in diffusion dialysis is only 6% of acid flux at optimum current density in electrodialysis. Critical parameters for economic feasibility are acid to wood ratio in hydrolysis, current efficiency, and membrane service life. Best case estimates project total costs for sulfuric acid recovery and loss of about $0.02 per pound of glucose produced.