Removal of lead, cobalt, and strontium by nanohydroxyapatite in aqueous environments

Abstract Nanomaterials provide a novel solution to remedial technologies for heavy metals and nuclear contaminants in aqueous environments. Nanohydroxyapatite has demonstrated high capacity for sorption of metal cations and nuclear contaminants under certain conditions. The method of synthesis, morphology, and aqueous environment can change the structural properties resulting in large variation in removal efficiency. In order to address batch discrepancies in material consistency, this study focused on sorption of three heavy metals (lead, strontium, and cobalt) in aqueous solution using commercially available nanohydroxyapatite. Initial lab batch testing was performed to test the sorption capacity of nanohydroxyapatite under defined conditions. Removal (%) by nanohydroxyapatite was highest for lead (99.98 ± 0.011), followed by cobalt (36.60 ± 1.27), and strontium (33.75 ± 1.83) in lab batch experiments. Removal efficiency was then examined in lead and strontium contaminated water samples collected from stream flow-through before and after contact with constructed wetlands at Savannah River Site in Aiken, South Carolina (USA). Removal (%) of lead and strontium was higher in environmental water samples (lead: > 99.99%, strontium: ≥ 73.16 ± 1.20%) compared to lab batch results despite similar pH and temperature. Results demonstrate efficient removal via mechanisms of ion exchange, dissolution/precipitation, and adsorption. By demonstrating enhanced contaminant removal in environmental stream samples compared to standard laboratory batches, these findings highlight the necessity of evaluating novel nanomaterials under realistic, diverse environmental conditions to validate their stability and accelerate their application as superior alternatives to current aqueous waste treatment technologies.