Purification of pentoses from hemicellulosic hydrolysates without neutralization for sulfuric acid recovery

Then conventional electrodialysis was performed to recover most of sulfuric acid (80%). The average faradic yield was quite good (80%) and the specific energy consumption of the electrodialysis stack was quite interesting (1.1 kW h per kg of H2SO4 recovered and 8.4 kW h per m3 of hydrolysate). Finally, the complete demineralization (conductivity < 10 μS·cm−1) and discoloration (420 nm absorbance < 0.01) of the sugars solution was performed by ion-exchange and an activated carbon polishing treatment. The sugars purity was close to 100% meanwhile the overall sugars recovery rate reach about 90%. Finally we checked that the reused sulfuric acid solution was as efficient as a fresh one in a second hydrolysis operation of wheat bran. Recovery rates could be increased by a scale-up operation or a continuous mode of the process.