Adsorption of Organic Dye on ZnCoAl-LDH: Modeling, Optimization and Kinetic and Isotherm Studies

The ZnCoAl layered double hydroxide (LDH) was synthesized by coprecipitation method. The as-prepared sample were characterized by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). Response surface methodology (RSM) was used to optimize, model and investigate the effect of operational parameters, namely LDH dosage, initial dye concentration, pH and time. Optimal experimental conditions for highest removal efficiency were found as [LDH] = 0.4 g/L, [Dye] = 112 mg/L, pH = 4.8 and Time = 66 min. The predicted degradation efficiency under the optimal conditions was 195 mg g-1. The proposed model was in accordance with the experimental results with R2 of 98.9% and adj-R2 of 97.9%. Equilibrium data were well-represented by the Freundlich isotherm model with Kf = 14.74 which confirms multi-layer adsorption. Kinetic studies showed that pseudo second order model describes the adsorption kinetic behavior well.