Abstract
This study investigates the development and performance of composite membranes incorporating In₂S₃/NH₂-MIL-125/IL for effective dye removal and degradation from textile wastewater. The nanocomposite's synthesis was confirmed using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and UV-Vis diffuse reflectance spectroscopy (DRS), demonstrating the successful integration of NH2MIL-125/IL (MI) and Ionic liquid (IL) into the In₂S₃ structure. The introduction of NH₂-MIL-125/IL into In₂S₃ reduced the crystallite size of the In₂S₃/NH₂-MIL-125/IL nanocomposites, with the surface area increasing as the NH₂-MIL-125/IL content rose. The ability to control the tetragonal and cubic phases of β-In₂S₃ using ionic liquids represented a significant advancement in nanomaterial design. The calculated ID/IG ratios for 1%, 3%, and 5% In₂S₃/NH₂-MIL-125/IL were 0.46, 0.46, and 0.14, respectively. The 5% In₂S₃/NH₂-MIL-125/IL composite exhibited the lowest ID/IG ratio, indicating fewer defects and higher crystallinity due to its higher NH₂-MIL-125/IL loading, which enhanced the material's structural integrity. A new FTIR peak at 913 cm⁻¹ in the In₂S₃/NH₂-MIL-125/IL composite suggested chemical interactions between In₂S₃ and NH₂-MIL-125. TEM images confirmed the preservation of the pristine structures, with In₂S₃ forming nanosheets, NH₂-MIL-125 adopting hexagonal structures, and In₂S₃/NH₂-MIL-125/IL displaying a combined morphology. The composites’ surface area increased significantly from 41.89 m²/g to 95.25 m²/g as the NH₂-MIL-125/IL content increased, attributed to NH₂-MIL-125’s intercalation on the In₂S₃ sheets. XPS, TEM, and EDX analyses supported the successful formation of the In₂S₃/NH₂-MIL-125/IL heterostructures. The 5% In₂S₃/NH₂-MIL-125/IL composite showed improved optical and photocatalytic properties, including a reduced band gap of 2.09 eV, a redshift in absorption, and reduced photoluminescence intensity, indicating lower charge recombination. Photocurrent tests revealed that 5% In₂S₃/NH₂-MIL-125/IL achieved the highest photocurrent density (0.018 mA/cm²), and Mott-Schottky analysis indicated that it had the lowest flat band potential (-1.43 V), requiring less energy to initiate photocatalytic processes. The composite’s photocatalytic performance was further enhanced by the formation of an S-scheme heterojunction, which facilitated
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electron migration and improved charge separation, making it promising for applications such as wastewater treatment.
Membranes fabricated with varying concentrations of In₂S₃/NH₂-MIL-125/IL showed significant improvements in both dye rejection efficiency and photocatalytic degradation, with M7 (1.2% In₂S₃/NH₂-MIL-125/IL) achieving up to 80% removal of Methyl Orange (MO) and 70% removal of Methylene Blue (MB). The optimal dye rejection occurred at pH 9, where electrostatic interactions between the membrane and dye molecules were strongest. The membranes exhibited a first-order kinetic degradation rate, with M7 demonstrating the highest photocatalytic activity up to 96% of MO and 93% of MB. The rejection efficiency for both dyes decreased with increasing dye concentration, with M7 maintaining over 70% removal for MO at concentrations up to 120 ppm. Membrane fouling tests with bovine serum albumin (BSA) indicated that the composite membranes, particularly M7, exhibited superior antifouling resistance, with a flux recovery ratio (FRR%) of 96.7% after backwashing, and over 50% of fouling being reversible. M7 demonstrated excellent long-term stability, retaining high performance after five cycles of backwashing and dye rejection, indicating its potential for sustainable use in wastewater treatment. This work highlights the enhanced efficacy of In₂S₃/NH₂-MIL-125/IL-based composite membranes for dye removal and photocatalytic degradation, with promising implications for industrial-scale wastewater treatment.