Membrane capacitive deionization for biomass hydrolysate desalination

• Membrane capacitive deionization is a low energy water desalination technology.
• This study for the first time applied MCDI for real complex process streams.
• Various MCDI tests with model as well as real biomass hydrolysates were performed.
• The technical feasibility of MCDI for hydrolysate desalination was demonstrated.
• This proof-of-concept broadens the potential application field for MCDI.

Biomass hydrolysates are rapidly gaining interest as low-cost non-food renewable feedstocks for fermentation processes. However, since high concentrations of salt such as sodium and potassium can act toxic to microorganisms, there is a need to remove these salts to maintain high biochemical productivity. In this study, the electrochemical treatment of biomass hydrolysates by membrane capacitive deionization (MCDI) was considered as an auxiliary chemical free, lower cost alternative in comparison to the commonly used ion-exchange processes. Model experiments performed with a commercial bench-scale MCDI set-up and model solutions indicated that none of the most abundant hydrolysate components (sugars, organic acids and furans) prohibited the implementation of MCDI for this application, although performance was lowered by the competition for electro-sorption between the protons deriving from organic acid dissociation and the cations. Such an effect was not observed during MCDI treatment of a real biomass hydrolysate sample. Instead, the results achieved in terms of Na and K removal and energy usage were very comparable to the ones for a model solution with equal conductivity and sugar concentration. As such, this study clearly demonstrates the technical feasibility of MCDI for process streams such as biomass hydrolysates, hereby considerably broadening its potential application field.