Amino/thiol-functionalized silica from coal fly ash for Cu²⁺ removal.

Area of Science:

• Materials Science
• Environmental Chemistry
• Nanotechnology

Background:

• Heavy metal copper (Cu²⁺) pollution poses significant ecological and health risks due to its persistence and bioaccumulation.
• Development of cost-effective and efficient adsorbent materials is crucial for controlling heavy metal contamination in water.
• Coal fly ash (CFA) is an abundant industrial waste material with potential for valorization into functional adsorbents.

Purpose of the Study:

• To synthesize and characterize novel mesoporous silica (MS) materials functionalized with amino (MS-NH₂) and thiol (MS-SH) groups from coal fly ash.
• To evaluate the adsorption performance of these functionalized MS materials for Cu²⁺ removal from aqueous solutions.
• To investigate the adsorption mechanisms and theoretical maximum adsorption capacities of the developed materials.

Main Methods:

• Mesoporous silica (MS) synthesized from coal fly ash (CFA) using sol-gel, sintering, and acid-leaching methods.
• Chemical grafting of MS with 3-aminopropyltriethoxysilane (APTES) and (3-mercaptopropyl) trimethoxysilane (KH-590) to create MS-NH₂ and MS-SH.
• Adsorption experiments to determine the effects of dosage, pH, concentration, and contact time; characterization using FT-IR, XPS, SEM-EDS, and BET; kinetic and isotherm modeling.

Main Results:

• The Si-O-Si framework of MS remained intact after functionalization.
• Optimized MS-SH achieved a Cu²⁺ adsorption capacity of 58.25 mg/g, outperforming MS-NH₂ (38.05 mg/g).
• Adsorption followed pseudo-second-order kinetics and the Freundlich isotherm model, with theoretical maximum capacities of 120.07 mg/g for MS-SH and 93.01 mg/g for MS-NH₂.

Conclusions:

• Functionalized mesoporous silica derived from coal fly ash are effective adsorbents for Cu²⁺ removal.
• MS-SH demonstrates superior adsorption performance due to synergistic complexation, electrostatic adsorption, and ion exchange mechanisms.
• This research provides novel materials and theoretical insights for utilizing coal fly ash in heavy metal remediation.