NH2@MoS2 impregnated MXene adsorbents for eliminating cationic dyes: Insight into pH, ionic strength and adsorption mechanism

Abstract

Herein, MXene/NH₂@MoS₂ adsorbent (MXMo-x) were facilely synthesized by introducing 3-aminopropyltriethoxysilane (APTES)-modified molybdenum disulfide (NH₂@MoS₂) into a MXene matrix through hydrothermal self-assembly and freeze-drying process. The abundant functional groups of NH₂@MoS₂ coupled with unique layer structure prevents the agglomeration of MXene, facilitates hierarchical porous structures formation, and promotes the specific surface area from 2.65 m²/g (MXene) to 8.27 m²/g (MXMo-6). This eventually leads to ultrahigh maximum adsorption capacities of 1170 mg/g for Malachite Green (MG) and 1050 mg/g for Crystal Violet (CV) at pH 10 due to the synergetic effect of electrostatic attraction, hydrogen bonding and pore filling. Particularly, the adsorption of MG and CV exhibited an insignificant decrease with the concentration of salt solutions (Na⁺, Mg²⁺), and the adsorption capacity of MG/CV in tap water and lake water also reached up to 961/867 mg/g and 842/732 mg/g, showing good salinity resistance and potential applicability in complex water systems. After five adsorption-desorption cycles, the adsorption capacity decreased by only 10 %, proving good recyclability of the adsorbents. Studies show that the adsorption process is a spontaneous endothermic process, which conforms to the quasi-second-order kinetic model (R² > 0.99) and the Freundlich isothermal adsorption model (R² > 0.91), revealing the process is primarily controlled by chemisorptions mechanisms. This study provides theoretical insights and technical references for the design of MXene-based composites and their application in dye wastewater treatment.