Reliable Identification of Relevant Factors for the Reactive Extraction of Succinic Acid from Electrolyte Containing Solutions

Reactive extraction of succinic acid by tertiary amines is an effective separation technique. Its potential application for the initial recovery of bio-based succinic acid from fermentation broth. However, the co-extraction of inorganic anions significantly impairs the extraction performance. In this study, we use a statistically backed design of experiments method (DoE) to screen and identify the factors with a significant effect and relevant impact on extraction yield and selectivity. Eight operational factors (Extractant, solvent, succinic acid concentration, amine concentration, initial pH, the type of anion, electrolyte concentration, and temperature) were screened by applying an orthogonal design plan for the experiments. The choice of the extractant and diluent as well as the type of anion had the most significant effect on the extraction yield. In contrast, the selectivity was mainly affected by the concentration ratios of succinic acid and electrolyte. The screening plan reduced the number of experiments from 1728 possible combinations to 72 experiments required to identify the factors while maintaining the significance of the identified effects. We suggest competing mass-action relationships between the pH-dependent protonation of amines and the complexation of succinic acid to explain the observed trends.