Hydrothermal–thermal conversion synthesis of hierarchical porous MgO microrods as efficient adsorbents for lead(ii) and chromium(vi) removal

Abstract

High crystallinity magnesium oxide (MgO) microrods with hierarchical porous structure (ranging from micropores to mesopores and macropores) and well-defined rod-like morphology have been successfully synthesized via a flux NaCl and surfactant nonyl phenol polyoxyethylene ether (NP-9) directed thermal decomposition of the hydrothermally derived magnesium oxalate dihydrate (MgC₂O₄·2H₂O) microrods. The successive and synergistic effect of NaCl and NP-9 assisted the thermal conversion and promoted the final formation of the well-defined porous MgO microrods with a specific surface area of 50.2 m² g⁻¹ and well preserved rod-like morphology of the MgC₂O₄·2H₂O precursor. The as-obtained porous MgO microrods were employed as efficient adsorbents for removal of heavy metal ions such as Pb(II) and Cr(VI) from aqueous solutions, and the removal efficiency of Pb(II) (original concentration: 50.0 mg L⁻¹) and Cr(VI) (original concentration: 1.0 mg L⁻¹) was up to 99.5% and 55.6%, respectively. Such well-defined MgO microrods with hierarchical porous structure can also serve as promising candidates for catalyst supports and even as a catalyst themselves in addition to their present waste water treatment applications in various fields.