Optimization of adsorption of methyl orange from aqueous solution by magnetic CoFe 2 O 4 /ZnAl-layered double hydroxide composite using response surface methodology

Abstract The CoFe 2 O 4 /ZnAl-layered double hydroxide (LDH) composite was successfully developed through a facile co-precipitation method, characterized, and applied as an effective adsorbent for the removal of methyl orange (MO) dye from aqueous solutions. The central composite design (CCD) of the response surface methodology (RSM) was employed to estimate and optimize process variables such as initial MO concentrations, solution pH, adsorbent dosage, and contact time. 98.878% adsorption efficiency was obtained at an initial concentration of 18.747 mg l −1 of MO, with an adsorbent dosage of 0.048 g, a solution pH of 2.770, and a contact time of 85.890 min. Analysis of variance (ANOVA) confirmed the significance of the predicted model (R 2 = 0.9844). Kinetic and equilibrium studies indicated that the experimental data for MO adsorption were best described by pseudo-second-order kinetic and Langmuir models. The maximum monolayer adsorption capacity of the CoFe 2 O 4 /ZnAl-LDH for MO was 42.3 mg g −1 .