Characterization, preparation, and uses of nanomagnetic Fe₃O₄ impregnated onto fish scale as more efficient adsorbent for Cu²⁺ ion adsorption

In this research, the Cu²⁺ ion adsorption from aqueous solution was investigated by fish scale (FS) and nanomagnetic (Fe₃O₄) loaded fish scale (MFS) from fishery biomass. We characterized the structure and morphology of synthesized magnetic adsorbent by Fourier transform infrared spectroscopy (FTIR), FESEM, and XRD. The FTIR and XRD tests confirmed the collagen fibers, apatite crystals, and nanomagnetite particles presence in the MFS structure. The isotherm models of Langmuir, Freundlich, and Dubinin-Radushkevich were exerted to the empirical equilibrium data, by which was found that the Langmuir equation have the best fit to the experimental data in comparison to the other isotherm equations. The maximum capacities of monolayer coverage of FS and MFS for adsorption of Cu²⁺ ions were achieved, respectively, 61.73 and 103.1 mg g^-1 based on Langmuir isotherm at 45 °C. It was also discovered that the Cu²⁺ ion adsorption onto MFS was totally a physisorption-controlled process. It was perceived that the model of pseudo-second order rate kinetics also could be applied for predicting of studied adsorption processes. Here, the adsorption was a spontaneous and endothermic process because of the negative and the positive values of ∆G⁰ and ∆H⁰, respectively. The reusability potential of the used adsorbents was studied, so that the results showed an efficiency of 76.5 and 83.92% for FS and MFS, respectively, after four adsorption-desorption cycles.