Synthesis of cubic mesoporous silica SBA16 functionalized with carboxylic acid in a one-pot process for efficient removal of wastewater containing Cu2+: Adsorption isotherms, kinetics, and thermodynamics

Abstract

Wastewater containing heavy metal ions, such as Cu²⁺, that are released into the environment will cause irreparable damage to the nature and human health of living. It is, therefore, absolutely crucial to remove these toxic ions from water. Herein, this paper utilizes the cyano group as a functional reagent to prepare carboxyl-functionalized SBA16 for adsorbing Cu²⁺ in water. In this paper, 2-cyanoethyltriethoxysilane is employed as a functionalizing reagent to prepare carboxyl-functionalized SBA16 through a one-pot method. The prepared material was characterized using various techniques, such as WXRD, TEM, FT-IR, and XPS. The results indicated that the introduction of the functionalizing reagent did not disrupt the original cage-like cubic mesoporous structure (Im3m symmetry) of SBA16. Crucial adsorption factors, namely pH, adsorbent dosage, Cu²⁺ initial concentration, and contact time, affecting the removal of Cu²⁺ were monitored and the optimum adsorption conditions were determined. Isotherm and kinetic investigations were conducted and a non-linear fitting method of experimental data was used to obtain isotherm and kinetic parameters. Maximum adsorption capacity reaches 181.3 mg g⁻¹ was achieved in 60 min at pH = 3. Adsorption kinetics and adsorption isotherm followed the pseudo-second-order (R² = 0.999) and Langmuir (R² = 0.999) models, respectively. This suggests that the adsorption process primarily involves chemisorption and monolayer coverage. Thermodynamic parameters showed the spontaneous and endothermic nature of the adsorption process. After 5 cycles, the adsorbent still maintains a good adsorption capacity for Cu²⁺. This suggests promising applications for the adsorbent in treating wastewater containing Cu²⁺.