Detail the molecular mechanism by which activated carbon removes taste and odor compounds from water.

Activated carbon removes taste and odor compounds from water primarily through a molecular mechanism called adsorption. Activated carbon is a highly porous material, meaning it contains an intricate network of tiny channels and voids called pores. These pores are categorized by size: macropores (largest), mesopores, and micropores (smallest, often comparable in size to the molecules being removed). This extensive internal pore structure provides an enormous surface area for interactions, which is crucial for its effectiveness. The taste and odor compounds in water are typically organic molecules, which are often non-polar or only slightly polar, and relatively small in size. When water containing these compounds passes through activated carbon, the compounds are drawn out of the water and onto the carbon's surface. This process of adherence to a surface is called adsorption, where the activated carbon acts as the adsorbent and the taste/odor molecules are the adsorbates. The primary forces driving this adsorption are hydrophobic interactions and van der Waals forces, which collectively constitute a type of physical adsorption known as physisorption. Hydrophobic interactions arise because water is a polar solvent, while many taste and odor compounds are hydrophobic (water-repelling) or less polar than water. The surface of activated carbon is largely non-polar and hydrophobic. Therefore, the system's energy is lowered when these hydrophobic taste and odor molecules leave the polar water environment and associate with the hydrophobic surface of the carbon. This 'like-attracts-like' principle helps to drive the molecules onto the carbon. Simultaneously, van der Waals forces act between the carbon surface and the adsorbate molecules. These are weak, short-range intermolecular attractive forces, including London dispersion forces, which occur due to temporary fluctuations in electron distribution creating instantaneous dipoles. Although individually weak, the immense internal surface area of activated carbon allows billions of these forces to act cumulatively, resulting in a strong binding effect that holds the adsorbate molecules firmly to the carbon surface. The taste and odor molecules first diffuse from the bulk water to the exterior of the carbon particles, then through the larger macropores and mesopores, and finally into the smaller micropores. The micropores are particularly effective because their dimensions are often similar to the size of the adsorbate molecules, maximizing the contact points for van der Waals forces and effectively trapping the molecules within the carbon's porous network. The overall capacity of the activated carbon depends on its total surface area and the distribution of pore sizes that effectively match the size of the target taste and odor compounds.