MEMBRANE SEPARATION OF ACID FROM LIGNOCELLULOSIC HYDROLYSATE

Abstract

Conventional bioethanol production process consists of four major steps: pretreatment, hydrolysis, detoxification and fermentation. Acid hydrolysis of lignocellulosic biomass is a crucial technique to break the rigid crystalline structure of lignocellulosic biomass into carbohydrate monomers. However, acid present in the hydrolysate inhibits the fermentation of the cellulosic liquor into bioethanol. Currently, over liming followed by precipitation is used in the pilot scale facilities. In the present work, the recovery of sulfuric acid from lignocellulosic hydrolysate by means of single cell electrodialysis is proposed for bioethanol production Henceforth, to increase the performance and decrease the cost of the process, effective electrochemical separation using ion exchange membranes was evaluated. The limiting current was determined by operating the electrodialysis unit in potentiostatic mode as with the increase in current, recovery of acid decreases. This is attributed to the enhancement of water dissociation as the limiting current density exceeds and equilibrium shift at the solution/ membrane boundary as more sulfate ions cross the anion exchange membrane. The effects of flow rates on the current efficiency were also investigated as increased flow rate increases the amount of ion removal while increasing the mean current. The concentration of the reducing sugars, i.e., glucose and xylose in the was examined before and after the run and after the dialysis run. It was reported that there was a minimal change in the concentration of both glucose and xylose. We have reported approximately 70% recovery of the sulfuric acid from lignocellulosic liquor at an optimal flow rate of 18ml/min at an advantageous limiting current of 1.5 mA. We also to check the total reducing sugar concentration and check the separation efficiency. The separation of sulfuric acid from lignocellulosic hydrolysate increased indicating the importance of number of cell pair as a vital parameter.