In this study, CaO was prepared from chicken egg shells. Then, to improve its properties, CaO/Fe 3 O 4 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/Fe 3 O 4 was suitable, spontaneous and exothermic.
a b s t r a c tIn this study, an activated carbon was derived from Phoenix dactylifera (ACPD) by a newly introduced method of oil submerging and was applied to eliminate Pb(II), Cd(II), and Ni(II) from aqueous solution. At initial pH of 6, temperature of 25°C, metal ions concentration of 10 mg/L, contact time of 100 min, and biosorbent dosage of 5 g/L, the maximum removal of 94.5, 92.4, and 90.3% were attained for Pb(II), Cd(II), and Ni(II), respectively. The Freundlich model was the best model for describing the data among other studied models. A pseudo-second order model showed a better description of the results than the pseudo-first order and intra-particle diffusion models. The enthalpy, entropy, and Gibb's free energy confirmed that the biosorption processes were spontaneous and exothermic. The reusability of ACPD was repeated six times and the reduction in biosorption capacity at the 6 th cycle was 3% less than the fresh ACPD. A real sample of shipyard wastewater was successfully treated using ACPD. Therefore, ACPD can be used as a suitable and affordable biosorbent for Pb(II), Cd(II), and Ni(II) ions removal from wastewaters.
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