Melamine Sponge Loading Improves the Separation Performance of Magnetic Hydroxyapatite for Pb(Ii) Adsorption

Using magnetic materials as adsorbents for wastewater treatment has attracted great attention due to the easy separation of adsorbents for reuse. However, how to efficiently separate magnetic materials especially with nano scales is still challenging. This study thus developed an innovative method to enhance the separation performance of magnetic hydroxyapatite (MP) by melamine sponge (MS) loading. It was found that even though the magnetic moments of MP decreased from 15.54 emu/g to 11.51 emu/g after MS loading, MS loaded MP (MPMS) exhibited better magnetic separation performance than MP. The analysis of adsorption isothermal suggests that the theoretical maximum adsorption capacity of Pb2+ by MPMS was 139.28 mg/g. Combined with the adsorption kinetics and thermodynamics analysis, the adsorption was principally categorized as a chemical, heterogeneous, and endothermic process. From the perspective of adsorption mechanism, cation exchange, electrostatic interaction, dissolution/precipitation, and surface complexation mechanisms contributed 70.96%, 4.39%, 6.10%, and 18.55%, respectively, to the total Pb2+ removal. The findings in this study provides an efficient and cost-effective solution to enhance the downstream separation of magnetic adsorbents for reuse