Assessment of NF and RO for the potential concentration of acetic acid and furfural from the condensate of eucalyptus spent sulphite liquor

Thin spent sulphite liquor (SSL) generated in pulp and paper mills is a biomass resource that is commonly concentrated and burnt. Still, the biorefinery concept may add value to the by-products contained in SSL. The goal of this work was to investigate the application of nanofiltration (NF) and reverse osmosis (RO) to the condensate of SSL (CSSL) produced by Eucalyptus globulus sulphite pulping in a Portuguese pulp mill, in order to separate acetic acid and furfural. CSSL permeation lab experiments were conducted in total recirculation, natural pH, 25 °C, and 26 bar, through several NF/RO membranes supplied by Alfa Laval, Microdyn-Nadir and Dow Filmtec. Alfa Laval RO99 showed a higher retention for acetic acid (89%) in comparison with DSS-HR98PP (84%) and NF97 (77%), despite its lower flux (28 kg h−1 m−2). The furfural retentions were 91–93% for the three membranes highlighted.

► Nanofiltration/reverse osmosis of eucalyptus spent sulphite liquor condensate from pulp mill.
► Permeation lab runs through Alfa Laval, Microdyn-Nadir and Dow Filmtec membranes.
► Alfa Laval membranes RO99 and NF97 showed the highest retention for furfural (92%).
► Higher retention of RO99 for acetic acid (89%) compared to NF97 (77%) at 26 bar.
► Higher permeation flux of NF97 (47 kg h-1m-2) compared to RO99 (28 kg h-1m-2) at 26 bar.