Sugar refining practice: Why is wood charcoal (activated carbon) used for decolourization in sugar processing?

Introduction / Context:
Decolourization is a key step in producing white sugar or refined syrups. Porous carbons such as bone char or activated wood charcoal remove color bodies formed from polyphenols, Maillard reaction products, and caramels.

Given Data / Assumptions:

• Charcoal presents very high internal surface area and pore structure.
• Sugar solutions carry a spectrum of organic chromophores and trace metals.
• Process is typically conducted after clarification and filtration.

Concept / Approach:

Decolourization proceeds via physical adsorption: van der Waals forces and pore size distribution allow selective uptake of color molecules. With time, the carbon exhausts and is regenerated or replaced. The mechanism is not oxidation, reduction, or chemical conversion in standard practice.

Step-by-Step Solution:

Verification / Alternative check:

Color removal correlates with iodine number/surface area of carbons. Analytical monitoring (ICUMSA color) demonstrates performance consistent with adsorption isotherms.

Why Other Options Are Wrong:

Oxidation, reduction, or “conversion to salts” are not the operative mechanisms under typical refinery conditions without added reagents.

Common Pitfalls:

Assuming “activated carbon” always oxidizes contaminants; in sugar, it primarily adsorbs them.

Final Answer:

Because it adsorbs colored impurities onto its high-surface-area pores