Abstract
Reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were synthesized in the present study by chemical deposition method and were then characterized by various methods, such as Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The nZVI/rGO composites prepared were utilized for Cd(II) removal from aqueous solutions in batch mode at different initial Cd(II) concentrations, initial pH values, contact times, and operating temperatures. Response surface methodology (RSM) and artificial neural network hybridized with genetic algorithm (ANN-GA) were used for modeling the removal efficiency of Cd(II) and optimizing the four removal process variables. The average values of prediction errors for the RSM and ANN-GA models were 6.47% and 1.08%. Although both models were proven to be reliable in terms of predicting the removal efficiency of Cd(II), the ANN-GA model was found to be more accurate than the RSM model. In addition, experimental data were fitted to the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms. It was found that the Cd(II) adsorption was best fitted to the Langmuir isotherm. Examination on thermodynamic parameters revealed that the removal process was spontaneous and exothermic in nature. Furthermore, the pseudo-second-order model can better describe the kinetics of Cd(II) removal with a good R2 value than the pseudo-first-order model.
Highlights
Heavy metals, being controversial in their definition, often refer to elements having atomic weights between 63.5 and 200.6, and a specific gravity greater than 5.0 [1]
Cd(II) removal by the nanoscale zero-valent iron (nZVI)/recduced graphene oxide (rGO) composites took place via the monolayer physical adsorption. The This calculated thermodynamics parameters exhibitions thatbythe process was spontaneous and study investigated the removal of the Cd(II)
Demonstrated that showed the mechanism for the removal solutions by using the Response surface methodology (RSM)
Summary
Heavy metals, being controversial in their definition, often refer to elements having atomic weights between 63.5 and 200.6, and a specific gravity greater than 5.0 [1]. Heavy metal pollution has been considered as a serious environmental problem during the past few decades [2]. Contamination of the ecological environment with heavy metals may occur via both natural and anthropogenic causes [3]. Cadmium (Cd) is regarded as one of the most toxic because of its high mobility and persistence, which can accumulate and can pose dangers to human health [4,5,6]. Exposure to Cd may cause damage to human organs, such as the kidneys, livers, lungs, immune and reproductive systems [7].
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