Which contaminants are commonly removed by adsorption methods?

Adsorption methods are particularly effective for removing a range of organic contaminants due to the way these processes interact with the adsorbent materials. In this case, the choice that includes cyanide, PCBs (polychlorinated biphenyls), pesticides, phenols, and solvents is aligned with the kinds of substances that are typically targeted by adsorption.

Adsorption occurs when contaminants adhere to the surface of an adsorbent material, which can include activated carbon and various other materials designed to capture organic molecules. The high surface area and porous nature of these adsorbents enhance their ability to attract and hold onto specific compounds, especially those that are hydrophobic or have complex organic structures.

The contaminants listed—cyanide, PCBs, pesticides, phenols, and solvents—are organic or organic-derived substances that can be effectively captured through this mechanism, making the first choice the most accurate in the context of common contaminants removed by adsorption techniques.

The other options do not align as closely with the typical applications of adsorption. Heavy metals, for instance, are more commonly removed by methods such as ion exchange or precipitation rather than adsorption. Organic acids, fulvic acids, and humic substances may not be effectively removed through adsorption to the same extent,