Abstract: Functionalized polymer adsorbents for removing impurities from a feed stream comprising an active pharmaceutical ingredient (API) include particles of functionalized with at least one functional moiety capable of binding one or more contaminants, the polymer being a macroreticular polymer and the functionalized polymer adsorbents having a pore volume of at least 0.65 cm3/g. Alternatively, the adsorbent can comprise a polymer functionalized with either 2,4,6,-dimercaptotriazine-ethylenedithiol (DMT-EDT) adduct, 2,4,6,-trimercaptotriazine-ethylenedithiol (TMT-EDT) adduct, or a combination thereof, and the polymer can be either a macroreticular polymer or a swellable polymer. The adsorbents can be used in either continuous or batch processes for removing contaminants from an API-containing feed stream wherein the contaminants can include elemental impurities, particularly palladium.