Box-Behnken design optimization of bimetallic-organic frameworks for effective removal of tartrazine food dye from aqueous solutions

Lanthanum and tin-based hetero bimetallic organic frameworks (MOFs) in the form of stacked nanorods (La/Sn@MOF) exhibit promising capabilities in removing the yellow dye Tartrazine (E102) from aqueous solutions. Various techniques such as SEM, XRD, XPS, FTIR, and BET were employed to assess the adsorbent, revealing a significant surface area of 736.82 m²/g. The study thoroughly investigated the impact of pH, initial dye concentration, adsorbent dose, contact time, and temperature on the elimination of E102 dye. The clearance of tartrazine follows the Langmuir isotherm and pseudo-second-order kinetics, with a maximum adsorption capacity of 694.72 mg/g according to the Langmuir isotherm model. The pHzpc value of 6.41 suggests favorable adsorption of anionic dyes like E102 dye at pH levels below 6.4. The adsorption process was characterized by adsorption energy of 29.46 kJ/mol, indicating a chemisorption process. Thermodynamic analysis revealed that the adsorption processes were both endothermic and spontaneous, as evidenced by the negative values for ΔG^o and positive values for ΔH^o. La/Sn@MOF proved to be a straightforward and effective method for treating industrial wastewater, with the added benefit of being reusable for up to five cycles. Interaction between La/Sn@MOF and E102 dye was found to involve hydrogen bonding, pore filling, and π-π interactions, among other mechanisms. Optimization of the adsorption procedure was achieved using the Box-Behnken Design method (BBD).