Modeling and optimization of atmospheric CO2 capture for neutralization of high alkaline wastewaters using response surface methodology

Abstract

Lab-scale stirrer bubble and lab-scale stepped continuous flow capillary columns were developed to neutralize lime precipitation treated slaughterhouse wastewater (SWW) and recover the volatilized ammonia, using atmospheric CO2. These experiments were carried out using central composite design based on the response surface methodology. The carbonation process occurred in both processes. For the bubbling process, numerical optimization indicated a final pH of 8 with calcium and ammonium nitrogen removals of 76.0 and 66.2%, respectively, applying 21 h, air flow rate at 65 L h−1, the stirring speed at 52 rpm, and SWW volume at 178 mL. It was also observed that increasing the air flow rate can avoid the stirring step. For the capillary process, a pH of 8.2 and calcium and ammonium nitrogen removals of 81.0 and 57.5% were achieved, applying a SWW flow rate at 1.2 mL min−1, air flow rate at 90 L h−1, and capillary area at 700 cm2. Under optimal conditions, the flow capillary column was able to neutralize different SWW volumes, 178–478 mL, without significant differences in the collected samples, with the operation time varying between 4.48 and 10.20 h, respectively.

Keywords

• Atmospheric CO2 capture
• Alkaline wastewater
• Capillary action
• Stirrer bubble column
• Slaughterhouse