Adsorptive Study of Cadmium Removal from Aqueous Solution Using a Coal Waste Loaded with Fe۳O۴ Nanoparticles

A coal waste sample loaded with Fe۳O۴ nanoparticles is employed as an efficient adsorbent to remove Cd from synthetic wastewater. The synthesized nanocomposite is characterized using the Fourier transform-infrared (FT-IR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. The visual analysis of the microscopic image shows that the mean size of the magnetite nanoparticles is about ۱۰ nm. The effects of the operating variables of the initial solution pH (۳-۱۱) and nanocomposite to pollutant ratio (۷-۲۳۳) are evaluated using the response surface methodology on cadmium adsorption. The process is also optimized using the quadratic prediction model based on the central composite design. The statistical analysis reveals that both factors play a significant role in Cd adsorption. The maximum Cd removal of ۹۹.۲۴% is obtained under optimal operating conditions at pH ۱۱ and nanocomposite/cadmium ratio of ۹۰ after ۲ h of equilibrium contact time. A study of the adsorption kinetics indicates that the maximum removal could be attained in a short time of about ۲ min following a first-order model. The isotherm investigations present that the Cd adsorption on the Fe۳O۴/coal waste nanocomposite has a linearly descending heat mechanism based on the Temkin isotherm model with the minor applicability parameters than the other isotherm models. The overall removal behaviour is attributed to a two-step mechanism including a rapid adsorption of cadmium ion onto the active sites at the surface of nanocomposite followed by a slow cadmium hydroxide precipitation within the pores over the nanocomposite surface.

کلیدواژه ها:

Coal waste ، Fe۳O۴ nanoparticles ، Nanocomposite ، Cadmium ، Kinetics