Removal of Pb(II) from Aqueous Solutions Using Magnetic Mesoporous Silica Nanocomposites: Modeling and Optimization Based on Response Surface Methodology

In the adsorption process of heavy metals, a major challenge is to design and develop adsorbent materials in an abundance of accessible adsorption sites with high affinity to achieve both fast adsorption kinetics and increased adsorption capacity for toxic contaminants. The removal of pollutants by mesoporous silica adsorbents is now in the limelight due to the nontoxicity and biocompatibility of these materials with the environment. In this study, a fibrous core-shell magnetic mesoporous composite (Fe۳O۴/SiO۲/KCC-۱) was successfully synthesized and used as a nano-adsorbent to remove Pb(II) from an aqueous solution. The adsorbent was characterized by employing TEM, SEM, FTIR, VSM, XRD, and N۲ adsorption–desorption techniques. According to the results, Fe۳O۴/SiO۲/KCC-۱ was successfully synthesized with an average pore diameter of ۷.۹۴ nm, a surface area of ۸۱۳.۰۷ m۲ g-۱, and a pore volume of ۱.۴۱ cm۳ g-۱. The response surface methodology (RSM) was then adopted in the central composite design (CCD) to optimize parameters of the adsorption process. The optimal conditions for Pb(II) adsorption were then determined at a temperature of ۸۰ °C, an adsorption dosage of ۰.۰۴ g L-۱, a pH ۵.۶, and the contact time of ۳۸ min. The removal rate of Pb(II) was ۹۰%. Studies of equilibrium and kinetics indicated that the adsorption process followed Langmuir’s isotherm and the pseudo-first-order model with correlation coefficients of ۰.۹۸ and ۰.۹۹, respectively. The maximum adsorption capacity of Fe۳O۴/SiO۲/KCC-۱ was reported ۵۷۴.۴ mg g-۱. Moreover, the thermodynamic parameters known as enthalpy (ΔH° = +۵.۸۴ kJ mol-۱), negative Gibbs free energy (∆G°) values, and entropy (ΔS° = +۲۳.۴۲ kJ mol-۱ K-۱) indicated that the adsorption was endothermic and spontaneous with the increased disorder at the solid–liquid interphase.

Keywords:

Magnetic Mesoporous Adsorbent , Central composite design , Isotherm , Kinetics , Thermodynamics