Thermodynamic study of heavy metal removal from aqueous solutions using a sustainable source

Abstract

Researchers are increasingly studying the extraction of mesoporous silica (mSiO₂) from natural sources as a sustainable and low-cost source in response to the growing demand for environmentally friendly materials worldwide. Because of their high silicon dioxide (SiO₂) content, natural rocks like diatomite, volcanic tuff, porcelanite, and kaolinitic clay are promising raw materials for the synthesis of mesoporous silica. Mesoporous silica is distinguished by its high surface area, tunable pore architecture, and ordered porous structure with pore diameters ranging from 2 to 50 nanometers. Even at low concentrations, recent research has demonstrated the high adsorption efficiency of mSiO₂, particularly the modified variants, in eliminating hazardous heavy metal ions like lead (Pb⁺²), cadmium (Cd⁺²), and hexavalent chromium (Cr⁺³). Because these ions are persistent in aquatic environments and bioaccumulative, they pose significant risks to human health and the environment. Thus, adsorption is an economical, simple, and efficient treatment method compared to other techniques such as reverse osmosis, membrane filtration, chemical precipitation, oxidation-reduction, and ion exchange. We used thermodynamic analysis, FTIR, FESEM, XRD, EDX, BET, and TEM techniques to successfully create and study mesoporous silica (mSiO₂). Then, under various circumstances, we evaluated the synthesized silica's capacity to remove the ions Pb²⁺, Cd²⁺, and Cr³⁺ from water samples. Including pH, initial concentration, and contact time, the most effective removal rates are obtained at a pH of 8 and a contact time of 60 minutes at a temperature of 298 K. We examined the adsorption.