Synthesis of a 3D hierarchical structure of γ-AlO(OH)/Mg–Al-LDH/C and its performance in organic dyes and antibiotics adsorption

Abstract

We demonstrated an efficient route to synthesize a novel 3D hierarchically porous superstructure composed of edge-to-face stacks of Mg–Al-layered double hydroxide nanosheets, directionally arranged γ-AlO(OH) nanowires and amorphous carbon by a facile biotemplate method. Its derived metal oxides with similar morphologies and high porosity could also be obtained by carbon removal through hydrothermal treatment followed by calcination. Materials characterization confirmed that the obtained nanostructures had uniform accessible mesopores of ∼2.7 nm, a high surface area of ∼288 m² g⁻¹, and a large pore volume of ∼0.66 cm³ g⁻¹. The formation of Al(OH)₃ seeds, Mg/Al molar ratio and the pH value during the hydrothermal process played major roles in the formation of such 3D hierarchically porous structures. The as-synthesized sample exhibited ultrafast adsorption rates and high adsorption capacities in the removal of anionic dyes and antibiotics from aqueous solution. The maximum adsorption capacities of Mg–Al-LDH/γ-AlO(OH)/C and its derived metal oxides towards minocycline (MC) and Congo Red (CR) were 302 and 447 mg g⁻¹, respectively. The adsorption process was well described by the Langmuir isotherm model and the pseudo second-order kinetic model. Electrostatic adsorption, ion exchange and π–π interactions were considered as the main adsorption mechanisms.