UTILIZATION OF CALCIUM BIOLEACHING RESULTS FROM PT KRAKATAU POSCO’S STEEL SLAG USING BACILLUS ALTITUDINIS FOR CARBON CAPTURE AND STORAGE BY FORMING CACO3 BIOMINERALS USING BACILLUS VELEZENSIS

• Main Author: Annabiila Risqulia, Nasha
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/77708
• Institution: Institut Teknologi Bandung

The national steel production is predicted to reach 15,8 million tons in 2023 by the Indonesian Iron and Steel Association (IISA). It will undoubtedly increase the production of steel slag as by-product and CO2 emission. Steel slag contains metal oxides that can be recycled, such as calcium. Calcium leaching can be carried out through the bioleaching process. The resulting Pregnant Leach Solution (PLS) can be utilized as calcium source for Microbially Induced Calcium Carbonate Precipitation (MICP) process, as an effort to address the global warming issues caused by greenhouse gas emission. Studies related to MICP and Carbon Capture and Storage (CCS) using the Carbonic anhydrase (CA) are currently being extensively developed. Hence, similar experiments are conducted using Bacillus velezensis bacteria with a calcium source derived from PT Krakatau Posco’s steel slag. Firstly, the optimization of leaching time for the bioleaching experiment is conducted to produce PLS as a calcium source for the CCS experiment. A series of CCS experiments have been carried out to study the effects of enzyme inoculum percentage, pH, and CO2 flow rate to carbonation process. The influence of CCS conditions is studied at enzyme inoculum percentages of 3%, 5%, and 10%; with agitation speed or 200 rpm; using CO2 flow rates of 0,05 L/min, 0,1 L/min, and 0,15 L/min; while maintaining the environmental pH at pH 9, pH 11, and initial uncontrolled pH 9. Each CCS experiment is conducted for 8 minutes. The percentage of converted calcium as function of time under various CCS conditions is periodically determined through Atomic Absorption Spectrophotometry (AAS) analysis. The highest calcium extraction percentage from steel slag through bioleaching using Bacillus altitudinis is 11,644% on the 24th day of leaching, and it significantly decreases from day 30 to day 39. The formation of CaCO3 biominerals through MICP by utilizing the CA enzyme from Bacillus velezensis occurs rapidly, reaching minute 2, ands shows no significant difference for the subsequent minutes. This is due ti the use of crude enzymes instead of pure enzymes. The fastest formation of CaCO3 biominerals in CCS conditions is achieved using CO2 flow rate of 0,15 L/min, 10% enzyme inoculum, and maintaining the pH at 9.