3D Hierarchical Layered Double Hydroxide-Based Micromotors for Motion-Based Adsorption and Efficient Removal of Tetracycline Hydrochloride and p-Nitrophenol

This paper reports a novel bioinspired 3D hierarchical sodium citrate (SC)–functionalized layered double hydroxides (LDHs)-based magnetic micromotor as an active self-propelled micromachine for the adsorption and removal of TCH or PNP from water. This micromotor was composed of MgAl-based layered double hydroxides intercalated with citrate anions (CA) and MgFe₂O₄ fiber/Mn₃O₄. The outer SC-functionalized MgAl-LDH layer functioned as a functional unit for TCH or PNP adsorption, MgFe₂O₄ fibers acted as a buffer layer, facilitating the nucleation and growth of MgAl-LDH. MgFe₂O₄ nanoparticles provided magnetism for recycling. Mn₃O₄ served as a catalyst in decomposing H₂O₂ for self-propulsion of the micromotor. The obtained micromotor exhibited a circle motion form with an average speed of 147.50 µm s⁻¹ in 5 wt% H₂O₂. Due to the cooperation of self-propelled movement with interlayer water repellency after SC intercalation, these micromotors exhibited a rapid removal rate of antibiotics or organic pollutants from water. The maximum adsorption capacities of SC-MgAl-LDH/MgFe₂O₄/Mn₃O₄ toward tetracycline hydrochloride (TCH) and p-nitrophenol (PNP) were 146.20 and 127.39 mg g⁻¹ in the presence of 5 wt% H₂O₂. Therefore, this study provides an efficient option for wastewater treatment.