Efficient adsorption of iodide from water by chrysotile bundles with wedge-shaped nanopores

Abstract Immobilization of iodide (I−) from groundwater and soils is a challenging subject due to the large size and low charge of I−. Clay minerals and (hydr)oxides generally exhibit very low adsorption capacity due to anion exclusion or weak attraction. For the first time, the adsorption of I− by chrysotile bundles (Chry-B) was investigated and a characteristic mechanism was established by comparing the adsorption of I− on Chry-B with dispersed chrysotile single nanotubes, lizardite and brucite. The adsorption of I− by Chry-B reached equilibrium with 24 h, and Chry-B exhibited very strong adsorption to I−, with a distribution coefficient (Kd) of 179.24 mL/g, which is two orders of magnitude higher than those for previously reported clay minerals. The Langmuir adsorption capacity of Chry-B was 4.13 mg/g. The wedge-shaped nanopores among the neighboring nanotubes in Chry-B proved to be the primary adsorption sites for I−. The I− at end of the wedge sites was strongly bonded by the nanopores due to the severe superposition of electric potentials from the charged walls of the narrowing wedges. These results demonstrated that chrysotile bundles were a promising candidate for adsorption of I−, and that the shape of nanopore geometry was crucial in I− adsorption.