Self-sacrificing/transitioning construction of defect-enriched coral-like magnesium oxide for highly efficient Pb(II) removal

Defect-enriched magnesium oxide with a specific structure exhibits great potential for the effective removal of heavy metals from wastewater. However, its practical application is significantly hindered by the high cost and tedious manufacturing process due to the reliance on templates and auxiliary agents. Herein, defect-enriched coral-like magnesium oxide (DFC-MgO) was synthesized via a self-sacrificing/transitioning strategy without using templates or auxiliary agents. The defects and coral-like structure endow DFC-MgO with abundant active sites and high porosity. Benefiting from these structural advantages, the DFC-MgO achieves an ultra-high adsorption capacity of 2955.07 mg/g for Pb ions in wastewater. Notably, lead contaminants can be completely removed with an extremely low dosage of 0.1 g/L at a typical concentration of 50 mg/L. In addition, DFC-MgO maintained high Pb 2+ removal efficiency in real water samples and effectively adsorbed multiple divalent metal ions. Dynamic adsorption tests further demonstrated that the effluent Pb 2+ concentration remained below the national standard limit of 1 mg/L for a treated volume of 1600 mL. Kinetic analysis indicated that adsorption occurs via a combination of chemisorption on heterogeneous sites and physisorption, while equilibrium behavior was best described by a combined Sips and Toth model, reflecting complex adsorption mechanisms. Several possible mechanisms, including ion exchange, precipitation, and oxygen vacancies, are involved in the Pb 2+ adsorption process. A preliminary cost evaluation further indicates that DFC-MgO can be prepared at a relatively low material cost. This study provides a facile approach for designing MgO with special structures and defect features for efficient wastewater treatment.