Facile hydrothermal assembly of three-dimensional GO-MTZE composite and its adsorption properties toward Cu²

Three-dimensional (3D) graphene oxide (GO)-based aerogels, GO and 4-methyl-5-thiazoleethanol (MTZE) composites, were prepared by a facile hydrothermal method. Due to the hydrogen bonding and π-π stacking interactions, the produced 3D GO-MTZE composites possessed large cylindrical structures. The morphologies, composition, and chemical states of 3D GO-MTZE_3:1 composite were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and N₂ adsorption-desorption isotherms based on the Brunauer-Emmett-Teller (BET) method. The existence of nitrogen (N)-containing heterocyclic system and oxygen (O)-containing branched chain of MTZE contributed to the formation of 3D structures, while the complexation effect of heterocyclic sulfur (S)- and N-containing functional groups of MTZE for metal cations dominated the adsorption performance of 3D GO-MTZE_3:1 composite, which could selectively adsorb copper ions (Cu²⁺). In addition, the better hydrophobic property of 3D GO-MTZE_3:1 composite facilitates its facile recycling from aqueous solution after adsorption. The adsorption data of 3D GO-MTZE_3:1 composite toward Cu²⁺ fitted well (R² = 0.9996) with the linear pseudo-second-order kinetic model, giving an equilibrium rate constant (k₂) of 0.0187 g mg^-1 min^-1. The linear Langmuir isothermal model could more accurately describe the experimental data, indicating the adsorption process is mainly dominated by the complexation interactions between MTZE and Cu²⁺. The thermodynamic parameters of ΔG° (< 0), ΔH° (> 0), and ΔS° (> 0) further indicate that the adsorption is a spontaneous and endothermic, confirming that the complexation between Cu²⁺ and 3D GO-MTZE_3:1 composite occurs. Due to its high selectivity for Cu²⁺, good hydrophobicity, and excellent stability, the developed 3D GO-MTZE_3:1 composite possesses might be promisingly used in the aqueous selective enrichment/removal of Cu²⁺.