(379b) Optimization of Process Parameters in Resin-Wafer Electrodeionization for Enhanced Gluconic Acid Recovery from Hemicellulose Hydrolysate

There has been significant interest in utilizing renewable biomass as a primary feedstock in pursuing sustainable and eco-conscious chemical processes. Hemicellulose hydrolysate is a byproduct of biomass processing, representing a promising resource for producing gluconic acid, a versatile compound with various industrial applications spanning pharmaceuticals, food additives, and industrial processes. In current biomass processing practices, gluconic acid recovery from hemicellulose hydrolysate remains inefficient due to suboptimal purification techniques. Conventional methods suffer from low yields, energy inefficiency, and impurity issues, limiting gluconic acid production's economic viability and sustainability.

In recent years, resin-wafer electrodeionization (RW-EDI) has emerged as a promising separation technology for recovering gluconic acid from complex aqueous streams. This process involves using ion-exchange resins and an electric field to facilitate the migration of ions across a selective membrane, thereby separating and concentrating target molecules such as gluconic acid. RW-EDI offers several advantages over traditional separation methods, including continuous operation, high purity, and reduced chemical usage. Despite its potential, the efficiency and cost-effectiveness of RW-EDI for gluconic acid recovery depend heavily on the optimization of process parameters. Factors such as current density, flow rate, pH, temperature, resin type, and membrane characteristics significantly influence the performance of the RW-EDI system. However, the complex interplay between these parameters and their optimal values for maximum gluconic acid recovery still needs to be explored.

Due to its simplicity and cost-effectiveness, ion-exchange resins are typically the primary method for acidifying organic salts. However, bipolar membranes (BM) favor a more environmentally friendly approach for converting acid salts into their acidic forms. This is because BM technology produces minimal chemical effluents, thus eliminating the need for cumbersome regeneration steps associated with ion-exchange technologies. The process of producing organic acids through BM has been extensively researched. This method relies on the capability of BMs to split water into hydrogen and hydroxyl ions at the membrane interface. Consequently, the acid salts dissociate, forming acids and bases with the H+ and OH- ions generated by the bipolar membrane.

The choice of incorporating a bipolar membrane within the RW-EDI system emerges as a pivotal component in facilitating the selective separation of ionic species, thereby enhancing the efficiency of gluconic acid recovery. By harnessing the unique properties of the bipolar membrane, we mitigated ion crossover and improved the separation of gluconic acid from the complex matrix of hemicellulose hydrolysate while promoting sustainability.

This work used high-pressure liquid chromatography (HPLC) to analyze concentrations of gluconic acid in the diluate and concentrate streams. By identifying critical process parameters such as flow rate, current density, applied voltage, ion exchange resin type, and hydrolysate concentration, the results showed that resin wafer electrodeionization improved the recovery of gluconic acid from hemicellulose hydrolysate, by maximizing efficiency and minimizing energy consumption.