Polyurethane sponge loading improves the suspension of magnetic materials without affecting the Pb(II) adsorption

Magnetic adsorbents are promising for wastewater treatment due to their easy separation with a magnetic field for recycling. This study aims to develop a novel magnetic adsorbent to further simplify the separation of magnetic adsorbents after adsorption to reduce operating costs for magnetic separation process. Thus, a lightweight sponge, magnetic hydroxyapatite modified polyurethane sponge (MPPS), was synthesized for Pb2+ adsorption by combining polyurethane sponge with magnetic hydroxyapatite (MP). The density of MP was about 4.23 g/cm3, while MPPS was only 0.46 g/cm3. As such, MP can float under the water surface, which is beneficial to the separation and Pb2+ adsorption in solutions. Meanwhile, the loading rate of MP on MPPS can reach 37.5 %, and the loading process had no obvious effect on the physical and chemical properties of MP. Through experiments and characterization, MPPS had 60.46 mg/g adsorption capacity for Pb2+ in the solution with a pH of 5, and the adsorption was identified as a mainly homogeneous and exothermic process. Moreover, the adsorption of Pb2+ by MPPS was mainly due to the electrostatic interaction and ion exchange, accounting for 51.60 % and 24.31 % of the total adsorption, respectively. This study developed a lightweight magnetic sponge, which could be easier used in the magnetic separation process than conventional magnetic materials.