Response Surface Methodology (RSM) for Statistical Optimization of Cd2+ Removal Using Modified Zn2Al-layer Double Hydroxide by Quinoline Yellow

Modified Zn2Al-layered double hydroxide (LDH) intercalated with quinoline yellow (Q) (Zn2Al-LDH/Q) was prepared by a facile and simple method and then used to remove of Cd2+ ions from water. The chemical composition and morphology of Zn2Al-LDH/Q were investigated by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy. Response surface methodology was employed to optimize the adsorption parameters of Cd2+. Such optimization was undertaken to ensure a high efficiency over the experimental ranges employed and to evaluate the interactive effects of the initial concentration of Cd2+, pH, adsorbent dosage, temperature and contact time in order to improve the conditions employed in the batch process. The analysis of variance (ANOVA) indicated that a second-order polynomial regression equation was the most appropriate polynomial for fitting the experimental data. The experimental confirmation tests showed a correlation between the predicted and experimental responses (R-2). The optimum adsorption parameters were predicted as an initial Cd2+ concentration of 35 mg l(-1), a pH value of 4.17, the adsorbent dosage of 0.03 g l(-1), a temperature of 32.5 degrees C and contact time of 51 min. Under optimum conditions, the highest adsorption efficiency and maximum adsorption capacity were 45% and 12.18 mg g(-1), respectively.