Optimization and Experimental Design of the Pb²⁺ Adsorption Process on a Nano-Fe₃O₄-Based Adsorbent Using the...

Magnetic Fe₃O₄ nanoparticles have been used as adsorbents for the removal of heavy-metal ions. In this study, optimization of the Pb²⁺ adsorption process using Fe₃O₄ has been investigated. The adsorbent was characterized by various techniques such as transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and Brunauer-Emmett-Teller (BET) analysis. The influence of process variables on adsorption of Pb²⁺ ions in accordance with p < 0.05 was investigated and analyzed by the Box-Behnken design (BBD) matrix with five variables (pH, adsorbent dose, initial Pb²⁺ ion concentration, contact time, and temperature). The pH and temperature were observed to be the most significant parameters that affected the Pb²⁺ ion adsorption capacity from the analysis of variance (ANOVA). Conduction of 46 experiments according to BBD and a subsequent analysis of variance (ANOVA) provide information in an empirical equation for the expected response. However, a quadratic correlation was established to calculate the optimum conditions, and it was found that the R ² value (0.99) is in good agreement with adjusted R ² (0.98). The optimum process value of variables obtained by numerical optimization corresponds to pH 6, an adsorbent dose of 10 mg, and an initial Pb²⁺ ion concentration of 110 mg L^-1 in 40 min at 40 °C adsorption temperature. A maximum of 98.4% adsorption efficiency was achieved under optimum conditions. Furthermore, the presented model with an F value of 176.7 could adequately predict the response and give appropriate information to scale up the process.