Selenite Removal from Aqueous Solution Using Silica-Iron Oxide Nanocomposite Adsorbents

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Industrial development leads to the discharge of toxic metallic ions, including selenium (Se), into water bodies.
• Selenium is an essential micronutrient but toxic at higher concentrations, existing as selenate and selenite.
• Limited research exists on effective selenium removal methods from aqueous solutions.

Purpose of the Study:

• To synthesize a novel nanocomposite adsorbent material using sol-gel method for selenite removal.
• To characterize the synthesized adsorbent material (SiO2/Fe(acac)3/NaF).
• To investigate the adsorption mechanism, kinetics, thermodynamics, and equilibrium of selenite onto the adsorbent.

Main Methods:

• Sol-gel synthesis of a nanocomposite adsorbent from sodium fluoride, silica, and iron oxide.
• Characterization using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX).
• Adsorption studies involving kinetic, thermodynamic, and equilibrium analyses.

Main Results:

• The synthesized nanocomposite adsorbent was characterized by SEM and EDX.
• Pseudo-second-order kinetics best described the selenium adsorption process.
• Sips isotherm best fitted the equilibrium data, with a maximum adsorption capacity of ~6.00 mg Se(IV)/g.
• Thermodynamic studies indicated a spontaneous and physical adsorption process.

Conclusions:

• The developed SiO2/Fe(acac)3/NaF nanocomposite is an effective adsorbent for selenite removal from aqueous solutions.
• The adsorption process is governed by pseudo-second-order kinetics and described by the Sips isotherm.
• The physical nature of the adsorption process, confirmed by thermodynamic parameters, suggests potential for regeneration and reuse.