Separation of acetic acid and reducing sugars from biomass derived hydrosylate using biopolymer blend polyethersulfone membrane

Rice husk derived hydrosylates was chosen to assess the performance of synthesized membrane on rejecting acetic acid, an inhibitor that limit the yield of ethanol during fermentation of feedstock. The objective of this research is to synthesize novel polyethersulfone (PES)-biopolymer blend membranes with different wt.% of biopolymers such as cellulose (CS) and chitosan (CH). The importance of hydrophilic modification by means of biopolymers was evaluated in terms of pure water flux, hydrophilicity, porosity and in terms of % solute rejection of organic acid and reducing sugars present in alkaline/acid hydrolysates of rice husk. Characterization of biopolymer blend PES membranes have been done using fourier transform infra-red spectroscopy (FTIR), X-ray diffractometry (XRD), contact angle analysis and scanning electron microscopy (SEM). In this work the effect of pH on membrane structure, permeability and retention for acetic acid and reducing sugars present in alkaline and acid hydrolysates by employing novel hydrophilicity enhanced membranes were studied. The observed retention of reducing sugar for alkaline hydrolysates was 97.6% and 94.5% for PES/CS and PES/CH membranes respectively whereas for acid hydrolysates sugar retention remained higher of about 98% and 99% for PES/CS and PES/CH blend membranes respectively. However, acetic acid retention for alkaline hydrolysates was observed less as compared to reducing sugars and thus 75–84% retention was found for PES/CS and PES/CH respectively. The results provide an insight that the biopolymer blend membranes acquired improved flux without compromising the rejection efficiency. The synthesized membranes were also found to operate close to nanofiltration (NF) with the trans-membrane pressure corresponding to ultrafiltration (UF) due to the retention of low molecular weight acetic acid from the alkaline hydrosylates.