Main content area

Detoxification of highly acidic hemicellulosic hydrolysate from wheat straw by diananofiltration with a focus on phenolic compounds

Fayet, Axel, Teixeira, Andreia R.S., Allais, Florent, Bouix, Marielle, Lameloise, Marie-Laure
Journal of membrane science 2018 v.566 pp. 112-121
acetic acid, artificial membranes, ferulic acid, fouling, furfural, hydrolysates, hydroxymethylfurfural, levulinic acid, lignocellulose, nanofiltration, osmotic pressure, pH, permeability, sugars, sulfates, sulfuric acid, vanillin, wheat straw
Nanofiltration was studied for detoxification of lignocellulose hydrolysates obtained in harsh conditions. A hemicellulosic hydrolysate obtained from sulfuric acid steam explosion of wheat straw and presenting very low pH (= 1) and high osmotic pressure (28 bar) was studied and 8 inhibitory compounds were followed, among which 4 phenolic compounds. Several polymeric nanofiltration membranes were compared for separation performances and permeabilities; DK membrane (GE Osmonics) proved suitable with high rejection of sugars (> 99%) and lower rejections of inhibitors. Acetic acid and furfural were quasi-fully transmitted whereas the rejection of compounds ranked as follow: HMF (5-hydroxymethyl-furfural) < coumaric acid < levulinic acid < vanillin < ferulic acid < syringaldehyde with values of 40%, 50%, 60%, 80%, 90% and 98%, respectively, at a permeate flux of 14 L h⁻¹ m⁻². Diafiltration was carried out at a transmembrane pressure of 26 bar until 3 DV (Diafiltration Volume) to complete detoxification, and continuous and sequential-dilution modes were compared. Thanks to the permeability of the membrane to the monovalent form of sulfuric acid HSO4⁻, effective transmembrane pressure was increased and pH reached 2. At 3 DV, both modes showed removal performances between 92% (acetic acid and furfural) and 25% (syringaldehyde). Irreversible fouling was observed, leading to 30% permeability loss after diafiltration.