Ceria nanoparticles for sustainable heavy metal water filtration

Among the major contaminants in polluted waters are heavy metals. Specifically, arsenic(V) and chromium(VI) are classified by the International Agency for Research on Cancer as Group 1 carcinogens to humans. Efficient and selective filtration systems for the removal of arsenic and chromium from drinking water sources and industrial waste are important for long-term protection of environmental and human health. Metal oxides such as ceria have been shown to remove heavy metals with efficiencies competitive with commercial filters. Owing to its high surface area, large number of arsenic and chromium ion binding sites, and reactivation via base wash, ceria nanomaterials have gained significant research attention. We have synthesized ceria micro/nanostructures with hollow-sphere and flower-like shapes by changing morphosynthetic parameters such as pH, solvent system, pressure, and temperature. Scanning electron microscopy with electron dispersive spectroscopy, infrared spectroscopy, and X-ray powder diffraction were used to characterize the structure and composition of the as-synthesized ceria, as well as elucidate possible adsorption mechanisms of chromium and arsenic ions to the ceria surfaces. Inductively coupled plasma – mass spectrometry was used to quantitatively determine removal efficiencies and maximum loading levels. Sequential heavy metal exposure and base wash experiments were performed to verify ceria recyclability. These studies inform ongoing research to realize new routes for heavy metal water filtration and to decrease the environmental and monetary costs associated with providing safe, clean drinking water to the world.