Kinetics, Isotherms, and Thermodynamic Studies on the Efficient Adsorption of Ionizable Organic β-Agonist (Ractopamine) in Aqueous Solution onto Mechanically Synthesized Copper (II) Isonicotinate Metal–Organic Frameworks [Cu (INA)2]-MOF

The adsorptive performance of mechanochemically synthesized copper (II) isonicotinate metal–organic frameworks ([Cu (INA)2]-MOFs) on ractopamine in water is reported. The MOF characteristic was revealed by Fourier transform infrared (FTIR), showing all the projected functional groups. The X-ray diffraction (XRD) diffractogram shows an excellent crystalline size of 39.78 nm. Morphology, shape, and size revealed from field emission scanning electron microscopy (FESEM) with energy dispersive X-ray (EDX) show a porous nature, revealing a rectangular bar-like shape with a rough surface that aids the retention of its porous nature with the elemental distribution graph. Ionizable organic compounds (like ractopamine with secondary amide and phenolic groups) contain acidic or basic functional groups that exist in the ionic state under the appropriate pH value for better removal. Evaluating the pH influence revealed the MOF’s performed better at an alkaline pH while the isotherm and kinetics fit pseudo-second-order and Langmuir models based on the statistical fits of R2, RMSE, and AIC, respectively. An excellent removal efficiency of 98% under 40 min was obtained with an adsorbate concentration of 40 mg/L and a dosage of 4 mg/g. The thermodynamics study confirmed the spontaneous, endothermic, and random nature of the process. The MOF’s high reusability even after six cycles proves the [Cu (INA)2]-MOF as an efficient adsorbent for the removal of ractopamine and in fact, for all β-agonists.