Bleaching Performance and Mechanism of Al-MCM-41 Tuned by Si/Al in Rapeseed Oil

Area of Science:

• Materials Science
• Chemical Engineering
• Food Science

Background:

• Traditional activated clay (AC) bleaching in oil refining has limitations, including poor selectivity, leading to micronutrient loss, high residual oil retention, and inadequate regenerability.
• Developing efficient and selective bleaching materials is crucial for optimizing edible oil refining processes and preserving nutritional value.

Purpose of the Study:

• To develop and evaluate mesoporous Al-MCM-41 (AM) adsorbents as an alternative to AC for edible oil bleaching.
• To investigate the adsorption performance, selectivity, and regenerability of AM adsorbents, focusing on pigment removal and micronutrient retention in rapeseed oil.

Main Methods:

• Synthesis and characterization of mesoporous Al-MCM-41 (AM) adsorbents with varying Si/Al ratios.
• Evaluation of AM adsorbents' bleaching performance against AC in terms of pigment removal (chlorophyll, lutein, β-carotene) and micronutrient retention (tocopherols, phytosterols, squalene).
• Analysis of adsorption kinetics, isotherms, and thermodynamics to elucidate the bleaching mechanism.

Main Results:

• AM25 (Si/Al = 25) exhibited the highest bleaching efficiency (92.3%), effectively removing pigments while retaining high levels of tocopherols (93.89%), phytosterols (98.73%), and squalene (96.32%).
• AM25 significantly reduced peroxide value and demonstrated superior adsorption selectivity compared to AC.
• Adsorption followed pseudo-second-order kinetics and Freundlich isotherms, indicating a spontaneous, endothermic, heterogeneous multilayer physical adsorption process governed by mesopores and acidic sites.

Conclusions:

• Mesoporous Al-MCM-41 (AM25) is a highly effective and selective adsorbent for edible oil bleaching, outperforming traditional activated clay.
• AM25 offers excellent micronutrient preservation, improved oil quality, and good regenerability (maintaining 83.31% efficiency after five cycles).
• The study highlights the potential of tailored mesoporous materials for sustainable and efficient oil refining.