Abstract: An adsorbent composition of a carrier coated with nanoparticles of zerovalent iron (“NZVI”) is disclosed. The NZVI are synthesized in situ using a tannin extract. Methods of making the adsorbent composition comprise providing a liquid stream; dispersing iron salts in the liquid stream to form an iron salt solution; adding a carrier to the iron salt solution to form a prepared stream; adding a tannin extract to the prepared stream to form a reaction stream; and forming the adsorbent composition in the reaction stream. Methods of reducing toxic metal ions in an aqueous stream are also disclosed. The methods comprise providing said aqueous stream; providing an adsorbent composition having a carrier coated with in situ nanoparticles of zerovalent iron (“NZVI”) therein; and contacting the aqueous stream with the adsorbent composition.