Synthesis of CaO/Fe3O4 magnetic composite for the removal of Pb(II) and Co(II) from synthetic wastewater

Abstract

In this study, CaO was prepared from chicken egg shells. Then, to improve its properties, CaO/Fe₃O₄ magnetic composite was synthesized and was used for the removal of lead (Pb (II)) and cobalt (Co (II)) ions from aqueous solutions. For this purpose, the effects of several parameters including pH, contact time, temperature, adsorption dosage and initial concentration of ions on the adsorption were studied. The optimum conditions of pH, contact time, temperature, adsorption dosage and initial concentration of Pb and Co ions were determined to be 6, 30 min, 25 °C, 2 g L^-1 and 5 mg L^-1, respectively. The best efficiency for the adsorption of lead and cobalt ions was found to be 97.24 and 94.32 %, respectively. To investigate the equilibrium behaviour of adsorbent, Langmuir and Freundlich models were used. Also, pseudo-first order and pseudo-second order kinetic models were applied for the consider­ation of kinetic behaviours of experimental data. Additionally, the thermo­dyn­amic parameters including enthalpy, entropy and Gibbs energy were calculated for the adsorption of these heavy metal ions. The results showed that Freund­lich isotherm model and the pseudo-second order kinetic model achieved the best match with the experimental data and the maximum adsorption capacities obtained from the Langmuir model were 227.27 and 217.39 mg g^-1 for lead and cobalt, respectively. Also, thermodynamics studies revealed that the adsorption process of lead and cobalt ions using CaO/Fe₃O₄ was suitable, spontaneous and exothermic.