Water resources contaminated by industrial dyes can pose a significant threat to the environment and human health. Herein, we conducted a study on the removal of cationic and anionic dyes, such as methylene blue (MB) and methyl orange (MO), using MIL-140A, a zirconium-based metal-organic framework. MIL-140A is synthesized in a Schlenk flask at 120 °C, whereas its conventional synthesis route involves a teflon-sealed autoclave at 220 °C, highlighting the cost reduction and lower equipment requirements of the low-temperature synthesis. The structure of MIL-140A is characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and nitrogen adsorption techniques. The optimal pH for the adsorption of two dyes by MIL-140A is pH 5–8 for MB and pH 3 for MO. The adsorption equilibrium can be reached within 60 min at room temperature, and the adsorption of both dyes on MIL-140A follows pseudo-second-order kinetics and Langmuir isotherm, and the maximum adsorption capacity of MO and MB by MIL-140A were 163.6 and 89.2 mg/g, respectively. Thermodynamic studies indicate an entropy-driven spontaneous process. The adsorption mechanism of MO and MB on MIL-140A is investigated using FT-IR and X-ray photoelectron spectroscopy. The adsorption of MO involves coordination between Zr and sulfonate, while MB adsorption occurs via π-π interactions. Additionally, MIL-140A exhibits better removal efficiency for MO from lithium battery wastewater compared to MB, primarily due to stronger coordination interactions than π-π interactions. These findings demonstrate that MIL-140A is a promising adsorbent for effectively removing both anionic and cationic dyes from water resources.
Developing advanced membrane materials, represented by MOF membranes, is crucial for the efficient separation of butane isomers, which are important petrochemical industrial raw materials. However, this area has received limited attention to date. In this work, MIL-140A series membranes were successfully prepared on α-Al 2 O 3 ceramic substrates by metal precursor induction method, and were attempted for the separation of butane isomers. The developed MOF membranes exhibit impressive performance in separating n-butane/isobutane mixtures, which is attributed to their appropriate sieve apertures and preferential adsorption of n-butane. This mechanism can be described as size-based sieving assisted by preferential adsorption. Owing to its smaller sieve aperture, the performance of MIL-140A-NH 2 membrane was superior to that of the MIL-140A membrane, showing a n-butane permeance of 136 GPU and an ideal selectivity of 25.4. The excellent separation performance was maintained under varying testing conditions, including operating temperature, operating pressure, feed composition, and testing duration. This work provides a useful reference for the development of membranes for industrial separation of butane isomers.
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