BIOLEACHING OF FENI SMELTING SLAG USING LYSINIBACILLUS SPHAERICUS SKC/VA-1 FOR BIOLOGICALLY CARBON CAPTURE AND STORAGE (BIO-CCS) APPLICATION

• Main Author: Aidyitul Rahmat, Pancha
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/85281
• Institution: Institut Teknologi Bandung

Indonesia as the world's largest nickel producer generates substantial quantities of ferronickel (FeNi) smelting slag, a material with significant environmental implications. To address this issue, this study investigated a sustainable approach to FeNi slag management through bioleaching and biologically carbon capture and storage (Bio-CCS). The research focused on extracting calcium, magnesium, and iron from FeNi slag sourced from PT Antam Tbk, utilizing Lysinibacillus sphaericus SKC/VA-1 bacteria to produce a calcium and magnesium rich pregnant leach solution (PLS) as a precursor for subsequent Bio-CCS processes. The bioleaching process was conducted for ten days utilizing a calcite solubilize medium. In 400 ml of bioleaching solution, FeNi smelting slag with a particle size of -200 +270 mesh was introduced until the pulp density attained 100 g/l. During the bioleaching experiment, vinegar was added to investigate its influence on calcium, magnesium, and iron extraction, quantified through atomic absorption spectrophotometry (AAS) measurements. The smelting slag, both before and after bioleaching, was characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy. In the Bio-CCS experiment, the bioleaching solution, termed PLS, was combined with carbonic anhydrase enzyme derived from spent medium cyanobacteria and subjected to CO2 gas injection for 480 seconds. pH levels were monitored periodically and adjusted using 1M NaOH. The investigated variables encompassed the percentage of carbonic anhydrase enzyme (0%, 3%, 5%, and 10%), pH (maintained at 9, maintained at 11, and unmaintained at 9), and CO2 gas flow rate (0.05 l/min, 0.1 l/min, and 0.15 l/min). The impact of these variables on the formation of CaCO3, MgCO3, and FeCO3 was assessed periodically through AAS. The results indicated that the addition of vinegar substantially enhanced calcium extraction from the slag, culminating in a maximum value of 33% on the sixth experimental day. XRF analyses revealed a reduction in the slag's calcium content from 1.01% to 0.96% and 0.93% following bioleaching with and without vinegar, respectively. Optimal conditions for the Bio-CCS process were established with a carbonic anhydrase enzyme concentration of 5%, a CO2 gas flow rate of 0.15 l/min, and pH maintenance at 11. Under these parameters, calcium and magnesium conversion to CaCO3, MgCO3, and FeCO3 attained peak efficiencies of 44%, 42%, and 96%, respectively.