Rinse, Recover, Repeat: pH-Assisted Selective Extraction of Phosphate and Metals with a Sponge Nanocomposite

Water polluted with excess phosphates and metals poses significant risks to human health and the environment. These elements, however, also hold value as nonrenewable resources essential for agriculture and renewable energy. Nanostructured sorbents, with their high surface area/volume ratio, offer a solution by enhancing sorption capacity and selectivity. Given this, we developed a sponge nanocomposite (SNC) consisting of a cellulose sponge coated with iron oxide nanoparticles. The SNC features a robust hierarchical porosity and structure more suitable for scaled deployment, while also minimizing byproducts and providing reusability. Tested in a flow-through column setup, it demonstrated the effective removal of phosphate, copper, and zinc. Selective recovery was then achieved by using a pH-assisted selective extraction approach, where phosphorus was recovered at a mildly basic pH, while metals were recovered at a mildly acidic pH. This process regenerates the adsorption sites on the SNC for subsequent reuse. The methodology exhibited in this report shows the potential for sustainable advancements in the circular economy, resource reclamation, and water treatment.