Facile one-pot preparation of AgIn₅S₈/MoS₂ composite for selective adsorption of methylene blue from aqueous solution

In this paper, AgIn₅S₈/MoS₂ was prepared simply by a one-pot hydrothermal method and employed in the selective removal of methylene blue (MB) from an aqueous solution. Synthesis conditions of the AgIn₅S₈/MoS₂ composite were optimized by surface area. The morphology and structure of the AgIn₅S₈/MoS₂ composite were also characterized by Fourier transform infrared spectroscopy, x-ray diffraction, nitrogen adsorption-desorption, x-ray photoelectron spectroscopy, and scanning electron microscope. It proved that petal-like nanostructures of MoS₂ were generated on flower-like AgIn₅S₈ and the surface area of the AgIn₅S₈/MoS₂ composite (170.1 m² g⁻¹) is much larger than both pure MoS₂ (8.4 m² g⁻¹) and pure AgIn₅S₈ (60.9 m² g⁻¹). Factors of pH and contact time affecting AgIn₅S₈/MoS₂ adsorption of MB were studied in detail. The adsorptive equilibrium times of AgIn₅S₈/MoS₂ for different concentration MB are all very fast within 60 min. The adsorptive kinetics, isotherms, and thermodynamics reveal that the adsorptive progress is well-described by the pseudo-second-order kinetic model and Langmuir isotherm equations and spontaneous and endothermic (∆G° < 0, ∆H° > 0, ∆S° > 0), respectively. The results imply that the AgIn₅S₈/MoS₂ composite with the maximum adsorptive capacity of 90.0 mg g⁻¹ at 25 °C could be used as a potential adsorbent for MB in acidic wastewater as well as printing and dyeing wastewater. Besides, it can also specifically adsorb methyl blue but not methyl violet under alkaline conditions.