Adsorption of acid orange 7 using green synthesized CaO/CeO2 composite: An insight into kinetics, equilibrium, thermodynamics, mass transfer and statistical models

Abstract

The present research reported the co-precipitation mediated synthesis of mixed metallic oxide composite, CaO/CeO2 using ultrasound-assisted extract of Eichhornia crassipes leaves. Fourier Transform Infrared Spectroscopy (FT-IR), Thermo-gravimetric/Differential Thermal analysis (TG/DTA), X-ray Diffraction (XRD), and Brunauer-Emmet-Tellet (BET) isotherms ensured the formation of the mixed oxide. Further, the CaO/CeO2 composite was tested in the anionic azo dye, Acid Orange 7 (AO7) removal process. The optimal removal of 92.68% was attained in the initial solution pH of 2.0 with the composite dosage of 0.1 g for 10 mg/L of AO7 concentration, operating at the temperature of 301 K. Response Surface Methodology (RSM) and Artificial Neural Network (ANN) techniques were employed to model the dye removal process. A second-order quadratic model from Box-Behnken Design (BBD) predicted and optimized the dye removal percentage with high degree of statistical accuracy (Fcal > Ftab at df=9; p < 0.0001). Likewise, a three-layered ANN model using the Levenberg–Marquardt backpropagation algorithm well predicted the dye adsorption process with the least root mean square error values (RMSE 0.3020). Further, the mean impact value (MIV) method identified pH0 as the most influential batch variable in the AO7 dye adsorption process.