Activated charcoal is not effective for which of the following substances?

• A. Water
• B. Mineral acids
• C. Sodium chloride
• D. Oxygen

Answer: (B)

Activated charcoal works by physically adsorbing substances onto its porous surface, and it’s most effective for many organic toxins and drugs that are nonpolar or mildly polar. Ionic or inorganic species don’t bind well to charcoal, so they aren’t removed from the gut by adsorption.

Mineral acids dissociate into ions in the gut, and these charged particles do not adhere to the charcoal surface. Because of this, ingestion of mineral acids isn’t mitigated by activated charcoal—the charcoal won’t bind or neutralize the acid effectively.

In contrast, water, inorganic salts, and gases like oxygen are not the kinds of substances charcoal is designed to trap, so they’re not targets of its action. The main takeaway is that the adsorptive mechanism of activated charcoal is suited to organic toxins, not inorganic ions like those from mineral acids, which is why mineral acids are not effectively treated with charcoal.