Adsorption and Removal of Industrial Dyes by Water-Stabilized Aluminum-Based Metal-Organic Frameworks

Pollution of water resources by industrial dyes can threaten environmental safety and human health even at low concentrations. We proposed the adsorption removal of a typical azo dye, Congo red (CR), by CAU-23, an aluminum-based metal- organic framework (MOF). To characterize CAU-23, X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and thermogravimetry (TG) were employed. An investigation of the impact of the material on the adsorption kinetics, thermodynamics, and ionic strength of CR was conducted. The results demonstrated that the quasi-second-order kinetic model and Langmuir isotherm were in harmony with our experimental sorption data. Additionally, thermodynamic parameters of adsorption such as enthalpy and free energy were evaluated. Nanoporous CAU-23 with excellent water stability and suitable pore size is well suited for capturing CR molecules. Importantly, through a comprehensive investigation of experimental and theoretical studies, CAU-23 forms pi-pi interactions and electrostatic attraction with CR molecules, characteristics that promote CAU-23 as one of the most promising adsorbents for the elimination of CR from water.