Siti Nurul Halifah Mohd Sani, Sofia Mazlan, Ramizah Kamaludin, Azieyati Hani Hussain, Siti Balqis Zulfigar, Husnul Azan Tajarudin
Calcium carbonate (CaCO₃) is widely utilized in construction, paper, pharmaceutical, and biomedical industries due to its abundance and valuable physical properties. However, conventional CaCO₃ production methods are energy-intensive and environmentally harmful, highlighting the need for sustainable alternatives. Microbially induced calcium carbonate precipitation (MICP) offers a sustainable alternative by harnessing microbial urease activity. This study explores Bacillus subtilis for MICP-driven CaCO₃ production from calcium chloride and calcium nitrate, focusing on domestic wastewater as a feedstock. Optimized conditions (20 g/L urea, pH 8, 30°C, 150 rpm) in synthetic medium yielded 2.47 g/L CaCO₃ with calcium chloride and 1.94 g/L with calcium nitrate tetrahydrate. Applying these conditions to domestic wastewater increased yields to 5.00 g/L and 3.53 g/L, respectively, demonstrating improved efficiency. Characterization by FTIR, SEM-EDX, and XRD demonstrated that the precipitation environment influences CaCO₃ polymorphs. FTIR confirmed carbonate bonds across samples, while SEM and XRD showed amorphous forms predominated in synthetic media and hybrid calcite-amorphous structures in wastewater-derived CaCO₃. EDX detected heavy metals such as lead, copper, chromium, and zinc in wastewater samples, highlighting MICP’s dual role in resource recovery and pollutant removal. These results underscore its potential to advance circular economy strategies through sustainable material production with industrial scalability. © 2025 Elsevier Ltd.
School of Industrial Technology, Bioprocess Technology Division, Universiti Sains Malaysia, Penang, Malaysia; Bioprocess Engineering Research Unit, Department of Biosystems Engineering, Faculty of Agricultural Technology, Universitas Brawijaya, Indonesia
