Effective Removal of Toxic Heavy Metal Ions from Aqueous Solution by CaCO3 Microparticles
Heavy metals are a common contaminant in water supplies and pose a variety of serious health risks to nearby human populations. A promising approach to heavy metal decontamination is the sequestration of heavy metal ions in porous materials; however, current technologies involve materials which can be difficult to synthesize, are high-cost, or are themselves potentially toxic. Herein, we demonstrate that rapidly synthesized calcium carbonate (CaCO3) microparticles can effectively remove high quantities of Pb2+, Cd2+, and Cu2+ ions (1869, 1320, and 1293 mg per gram of CaCO3 microparticles, respectively) from aqueous media. The CaCO3 microparticles were characterized with powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Brunauer–Emmett–Teller (BET) N2 sorption–desorption. It was found that the Ca2+ ions of the microparticles were replaced by the heavy metal ions, leading to partially recrystallized nanoparticles of new compositional phases such as cerussite (PbCO3). The adsorption, surface dissolution/re-precipitation, and nucleation/crystal growth mechanisms were determined by investigating the Ca2+ released, along with the changes to particle morphology and crystal structure. Importantly, this study demonstrates that the porous CaCO3 microparticles performed well in a system with multiple heavy metal ion species: 100% of Cu2+, 97.5% of Pb2+, and 37.0% Cd2+ were removed from an aqueous solution of all cations with initial individual metal concentrations of 50 mg/L and 1.5 g/L of CaCO3 microparticles. At this concentration, the CaCO3 microparticles significantly outperformed activated carbon. These results help to establish CaCO3 microparticles as a promising low-cost and scalable technology for removing heavy metal ions from contaminated water.
KeywordsCalcium carbonate Porous microparticles Heavy metal adsorption Adsorption mechanisms
R. Zhang thanks the University of Sydney for a scholarship for her PhD study and the scientific and technical assistance, of the Australian Centre for Microscopy and Microanalysis (ACMM) Research Facility at the University of Sydney. Dr. Alexander K.Y. Yuen is acknowledged for his assistance with N2 sorption–desorption isotherm analysis. Dr. Shane Wilkinson is acknowledged for his support of ICP-OES analysis. Dr. Kang Liang acknowledges the support from the Scientia Fellowship program at UNSW.
- Annadurai, G., Juang, R., & Lee, D. (2003). Adsorption of heavy metals from water using banana and orange peels. Water Science and Technology, 47, 185–190.Google Scholar
- Charerntanyarak, L. (1999). Heavy metals removal by chemical coagulation and precipitation. Water Science and Technology, 39, 135–138.Google Scholar
- Jambor, J. L., Puziewicz, J., & Roberts, A. C. (1999). New mineral names. American Mineralogist, 84, 685–688.Google Scholar
- Yavuz, O., Guzel, R., Aydin, F., Tegin, I., & Ziyadanogullari, R. (2007). Removal of cadmium and lead from aqueous solution by calcite. Polish Iournal of Environmental Studies, 16, 467.Google Scholar