Efficient adsorption of fluorescein dye from aqueous solutions by Al/Th-MOF bimetal-organic frameworks: Adsorption isotherm, kinetics, DFT computation, and optimization via Box-Behnken design

Bimetal-organic frameworks, or MOFs, have sparked a lot of interest in the wastewater treatment industry. This study investigated the possibility of removing fluorescein dye (FS) employing bimetal-organic frameworks based on aluminum and thorium (Al/Th-MOF) from aqueous solutions. To investigate the properties of the material further, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, surface charge analysis, and X-ray diffraction (XRD) were used. Using these methods, we were able to identify the Al/Th-MOF's point of zero charge. Following adsorption, the adsorbent's large surface area of 2273.8 m²/g and pore volume of 1.4 cm³/g drop to 1678.9 m²/g and 0.96 cm³/g, individually. As this suggests, it is ideal that a portion of the FS was absorbed within the pores of the adsorbent. Through batch testing, it looked into the connection between adsorption equilibrium and pH levels, and found that changes in solution pH significantly affected adsorption behavior. Further studies with kinetic models led to the discovery of the pseudo-second-order model for FS adsorption on Al/Th-MOF. Furthermore, the Langmuir isotherm model accurately describes the adsorption process, suggesting that chemisorption played a major role in the process as a whole. To optimize factors such adsorbent dosage, time, solution pH, the response surface methodology (RSM) and Box-Behnken design (BBD) were used. As a consequence (ΔH°), (ΔS°), and (ΔG°) data the adsorption of FS employing Al/Th-MOF as an adsorbent is endothermic and spontaneous. Our study's studies have demonstrated that the Al/Th-MOF adsorbent combines a number of mechanisms, such as π-π interaction, H-bonding, pore filling, and electrostatic contact, to effectively remove FS dye from water-based solutions. The adsorption capacity of FS onto Al/Th-MOF reaches a maximum of 668.6 mg.g⁻¹ at a pH value of 4, demonstrating that the adsorbent is particularly successful in removing FS from wastewater samples. Furthermore, the synthesized Al/Th-MOF adsorbent possesses outstanding render ability and cyclability for a maximum of eight adsorption-desorption cycles, suggesting that it could find application as an adsorbent in industrial environments. Overall, our research suggests that the adsorbent is a potential and novel approach for managing industrial effluent and water filtering.