Single- and Multicomponent Siloxane Adsorption in Al-MCM-41 (Al = 0.0, 1.3, and 4.4).

Area of Science:

• Materials Science
• Environmental Chemistry
• Adsorption Science

Background:

• Siloxanes, both linear and cyclic, are environmental contaminants.
• Silica MCM-41 and its aluminum-doped variants are mesoporous materials with potential for pollutant adsorption.

Purpose of the Study:

• To investigate the adsorption of linear (L5) and cyclic (D4, D5, D6) siloxanes on pure and Al-doped silica MCM-41.
• To evaluate the influence of adsorbent properties and siloxane characteristics on adsorption capacity and kinetics.
• To assess the reusability of the adsorbent for practical applications.

Main Methods:

• Synthesis of pure and Al-doped MCM-41 via sol-gel method.
• Characterization using XRD, SEM-EDS, ICP-OES, FT-IR, N2 adsorption-desorption, NH3-TPD, and NMR.
• Liquid-phase adsorption experiments in single- and multi-component systems at 25 °C.
• Adsorption kinetics and recovery tests.

Main Results:

• Al-MCM-41(10) exhibited the highest adsorption capacity for all siloxanes compared to Al-MCM-41(30) and MCM-41.
• Adsorption capacity order was L5 > D4 > D5 > D6, influenced by siloxane structure, geometry, and adsorbent acidity.
• Pseudo-first-order kinetics described the adsorption process, and Al-MCM-41(10) maintained 76-100% capacity after three uses for D4 adsorption.

Conclusions:

• Al-doped silica MCM-41 is a highly effective adsorbent for linear and cyclic siloxanes.
• The material's properties, including acidity and pore structure, significantly impact adsorption performance.
• The developed adsorbent offers a promising, cost-effective, and reusable solution for siloxane removal.