Preparation and Cationic Dye Adsorption of Novel Fe₃O₄ Supermagnetic/Thiacalix[4]arene Tetrasulfonate Self-Doped/Polyaniline Nanocomposite: Kinetics, Isotherms, and Thermodynamic Study

In this study, a novel magnetically separable nanoadsorbent, namely, Fe₃O₄@PAmABAmPD-TCAS consisting of a magnetite core and conductive terpolymer of aniline/m-aminobenzoicacid/m-phenilendiamine shell which was self-doped by protonic acid of thiacalixarene tetrasulfonate pendent groups has been synthesized in a three step procedure. Adsorption features of the magnetic nanoadsorbent were evaluated by using methylene blue (MB) and malachite green (MG) as adsorbates. The isotherms, kinetics, and thermodynamics of the adsorption of MB and MG onto Fe₃O₄@PAmABAmPD-TCAS nanoadsorbent have been studied in various experimental conditions, i.e., initial dye concentration, contact time, solution pH, adsorbent dosage, and temperature. The obtained results fitted well to the Langmuir model and the kinetics of the adsorption process were found to follow the pseudo-second-order kinetics. The synthesized nanoadsorbent revealed improvements in terms of adsorption capacity for the dyes as a result of its high surface area and large amount of functional groups. The thermodynamic study was conducted by calculating a number of thermodynamic parameters such as the standard Gibbs energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) changes. The high sensitivity of the magnetic nanoadsorbent to external magnetic field culminates in its efficient and easy separation.