Removal of pollutants by olive stones-derived activated carbon@Fe₃O₄ nanocomposites: Effect of calcination temperature on adsorption properties

This work focuses on preparing nanocomposites based on activated carbon as a matrix obtained from bio and natural source olive stones calcined at different temperatures (300,450 and 600 °C) and decorated with an ultrasonic dispersion of magnetite Fe₃O₄. The obtained materials (CA-300@Fe₃O₄, CA-450@Fe₃O₄, CA-600@Fe₃O₄) were used as adsorbents for the elimination of organic and inorganic pollutants, such as dyes (Methylene blue (MB) and Orange G (OG)) and heavy metals (Copper (Cu(II)), Nickel (Ni(II))), by varying various influencing factors (concentration, pH, temperature, contact time effect), and the adsorption data were analysed using two kinetic models (pseudo-first order and pseudo-second order) and two isotherm models (Freundlich and Langmuir). Different characterisation methods, such as FTIR, XRD, nitrogen adsorption–desorption, TGA, SEM, TEM, EDS, and zeta potential, were used. The experimental data show that all synthesised materials have proven their efficiency in the adsorption of both organic and inorganic pollutants even after five reuse cycles without any regeneration treatment. The study showed that all nanocomposites follow the Langmuir isotherm and the pseudo-second-order as kinetic model for both organic and inorganic pollutants. The most efficient nanocomposite was CA-450@Fe₃O₄ with a maximum adsorption capacity Q_max (564.97, 404.85, 787.4 and 625 mg/g) for the elimination of MB, OG, Cu, and Ni, respectively.