Effective removal of the rare earth element dysprosium from wastewater with polyurethane sponge-supported graphene oxide–titanium phosphate

Recycling methods will be essential for the future circular economy in the context of declining natural resources. Nanomaterials are promising adsorbents to recover rare earth elements from wastewater, yet the practical application of nanomaterials is limited by spontaneous agglomeration, easy collapse of structures and the difficulty in collecting nanomaterials after adsorption. To solve these issues, we prepared a polyurethane sponge-supported titanium phosphate with graphene oxide, abbreviated as GO@TiP-Sponge, by in situ precipitation. GO@TiP-Sponge was characterized by X-ray diffraction, scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, and tested for the removal and recovery of trace dysprosium Dy(III), a rare-earth element, in water using batch experiments. Results show that the GO@TiP-Sponge showed an excellent affinity for dysprosium with theoretical capacity reaching 576.17 mg/g according to the Langmuir model. Half-equilibrium was reached in 2.5 min according to a pseudo-second-order model. GO@TiP-Sponge also displayed an adsorption ability for a wide range of pH and salinity. Such performance is explained by strong binding of phosphate with Dy(III), enhanced surface area induced by graphene oxide and less aggregation from the spongy structure. The main adsorption mechanism involves electrostatic interaction.