Removal of acetic acid and sulfuric acid from biomass hydrolyzate using a lime addition–capacitive deionization (CDI) hybrid process

Abstract

In this study, we developed a lime addition–capacitive deionization (CDI) hybrid process that can efficiently remove acetic acid and sulfuric acid from the model mixture of glucose, xylose, acetic acid, and sulfuric acid, which are the major components from the biomass hydrolyzate by acid hydrolysis. The key parameters of lime addition process (type of lime, amount of lime, stirrer speed, and reaction time) and CDI process (voltage, flow rate, and feed concentration) were also optimized. In the lime addition process, the optimal lime type, (sulfuric acid+acetic acid)/lime molar ratio, stirrer speed, and reaction time for the removal of sulfuric acid were CaCO3, 1:1, 200rpm, and 6min, respectively. For the CDI process, the optimal voltage and flow rate were 1.2V and 20mL/min, respectively. The efficiency of acid removal increased as the initial acetic acid concentration decreased. This hybrid process was able to remove 98.08% of sulfuric acid and 76.97% of acetic acid from the mixture of glucose, xylose, acetic acid, and sulfuric acid. The process was able to recover almost all sugar (>99%) at high purity (97.53%).