Facile preparation of 3D porous graphene-based composite hydrogels doped with different ratios of MXene for MB adsorption

Abstract

The 3D porous structure of graphene functional materials possesses characteristics such as high porosity and large specific surface area, enabling dye molecules to easily enter and diffuse within the 3D network, thereby emerging as a promising solution for treating dye wastewater pollution. In this study, graphene@MXene composite hydrogels with a 3D porous structure were prepared using the hydrothermal reduction method with MXene and graphene oxide as raw materials, and their adsorption performance towards MB was investigated. The morphology and structure of the graphene@MXene composite hydrogels were examined through SEM, EDX,FT-IR, and BET analysis techniques. The graphene@MXene composite hydrogels doped with 20 wt% MXene exhibited the best removal efficiency for MB, showcasing excellent adsorption performance following the introduction of MXene. It is noteworthy, however, that as the proportion of MXene increased, there was a noticeable decrease in the adsorption performance of the composite hydrogels towards MB. During the preparation of the composite hydrogel, the introduction of Ca²⁺ as a cross-linking agent not only reduced the preparation time but also adjusted the specific surface area and pore size distribution of the hydrogel. As a result, there was an approximately 30% increase in the MB adsorption rate. The adsorption kinetics results revealed that the adsorption of MB on the graphene@MXene composite hydrogels, both pre- and post-introduction of calcium ions, conformed to a pseudo-second-order kinetic model. This observation suggests that the adsorption process is influenced by various mechanisms such as external diffusion, surface adsorption, and internal diffusion. Our study further revealed that the microwave irradiation spectra of 3D graphene@MXene composite aerogels changed before and after MB adsorption, exhibiting characteristic features of graphene or MXene. This finding confirms the adsorption of MB, suggesting a potential new method for its detection. This research demonstrates promising applications in both dye wastewater treatment and the detection of MB.