Evaluation of bovine carbonic anhydrase for promoting CO2 capture via reaction with KOH and high-salinity reject brine

In this study, we investigate the preliminary effect of bovine carbonic anhydrase (BCA) catalyst on CO2 capture via a reaction with potassium hydroxide (KOH) and reject brine under different operational conditions. Experiments were performed at a constant gauge pressure of 2 bar, with a CO2 inlet concentration of 10% and a CO2 flow rate of 776 mL/min. First, the impact of the BCA catalyst on CO2 capture in the absence of the alkaline material (KOH) was studied. Results showed that using 3-mg/L BCA increases the CO2 capture by 181% compared with the case without BCA. Second, the effect of BCA on CO2 uptake and ions reduction was examined in the presence of KOH. At a KOH concentration of 10-g/L, BCA concentration of 50-mg/L, and temperature of 40℃, a CO2 uptake value of 0.08 g CO2/g KOH was obtained. In comparison, adding 30-g/L KOH and 50-mg/L BCA increased the CO2 uptake by 737.5% (0.67 g CO2/g KOH). Furthermore, the sodium (Na+) reduction percentage reached a maximum of 40.8% at KOH and BCA concentrations of 30 g/L and 50 mg/L, respectively. However, increasing the BCA concentration to 100 mg/L negatively impacted CO2 capture and ion removal, indicating that the BCA concentration could be better optimized to achieve maximum efficiency. Additionally, when the BCA concentration was increased from 50 to 100 mg/L, the reaction rate remained nearly constant at 0.0047 mol/L·min.