Glycine and Boric Acid Promoted Accelerated Weathering of Limestone (AWL) Process for CO2 Absorption

Abstract The accelerated weathering of limestone (AWL) process is an efficient, cost-friendly, and eco-friendly CO 2 capture technology. However, the low bicarbonate content measured as alkalinity of its produced effluent can cause up to 50% of its captured CO 2 to re-enter the atmosphere within one year. To remedy this limitation, this study investigates the use of promoters (i.e., glycine and boric acid) in increasing the reactivity of the AWL process to elevate the effluent’s alkalinity. This work includes the correlation analysis and optimization analysis for promoted AWL to determine the optimum pH and promoter concentration. The correlation analysis revealed that increasing promoter concentration and pH enhance the effluent’s bicarbonate concentration. Based on the established correlation, the design of experiment (DoE) software with a two-level-two-factor central composite configuration was utilized to optimize the process. It was determined that the optimized glycine-promoted condition of 0.27 M and pH 11.52 achieved a maximum bicarbonate concentration of 53,200 mg/L as CaCO 3 with an enhancement factor of 652. As for the boric acid-promoted AWL process, the highest bicarbonate concentration achieved was 42,100 mg/L as CaCO 3 , with an enhancement factor of 525 at 0.50 M and a pH of 11.84. In addition, the regeneration potential of the promoters via the addition of Ca(OH) 2 was investigated. It was found that up to 49.68% of glycine can be regenerated, while an approximately 9% regeneration efficiency of colemanite (raw material of boric acid) was achieved. Overall, the study demonstrates the potential of using promoters to improve CO 2 capture efficiency in the AWL process, with both glycine and boric acid showing promising results under optimized conditions.