Powdered Activated Carbon (PAC) is used in water treatment to achieve removal of contaminants primarily through which mechanism?

• A. Adsorption
• B. Absorption
• C. Filtration
• D. Sedimentation

Answer: (A)

Powdered activated carbon removes contaminants mainly through adsorption—a surface-based attraction where dissolved molecules cling to the large surface area and internal pores of the carbon. The powdery form provides an enormous area of contact, so as water passes through, organic compounds, tastes, odors, and other dissolved contaminants are drawn onto and held on the carbon surfaces and within its pore structure. This is different from absorption, where substances would be taken into the interior of the material like a sponge; PAC works by binding contaminants to the surface and pores rather than soaking them into the carbon. Filtration and sedimentation remove particles based on size or density, not dissolved substances, so they’re not the primary removal mechanism for PAC.