Mg‐doped CaCO ₃ nanoarchitectures assembled by (441¯) high‐index facets for efficient trace removal of Pb(II)

Abstract

Abstract Removal of trace heavy metal ions puts high demands on designing adsorbents with favorable surfaces. Crystal‐plane engineering can provide controllable adsorption energy between surficial planes and adsorbents. Herein, we have creatively synthesized Mg‐doped CaCO 3 nanoarchitectures assembled by layered sheets (Mg‐CaCO 3 LSs) with high‐index facets of () through a facile wet chemical process. Adsorption tests reveal that the layer‐by‐layer assembled sample exhibits a maximum Pb(II) adsorption capacity of 1961.9 mg·g −1 , agreeing with the monolayer‐adsorption Langmuir model. At an initial Pb(II) ion concentration of 20 mg·L −1 , the adsorption can achieve a high removal rate near 99.0% within 1 min, and the adsorption kinetics follows a chemisorption pseudo‐second‐order model. Interestingly, the Mg‐CaCO 3 LSs show much‐improved adsorption properties towards low‐concentration Pb(II) ions, which could reduce the concentration from 1 mg·L −1 to ~ 2.9 μg·L −1 in 3 h (within 30 min decrease to less than 10 μg·L −1 , meeting drinking water standard from WHO). For comparison, the commercial CaCO 3 and collected CaCO 3 scale show much lower adsorption values with Pb(II) ion residual concentration of ~ 935.0 and ~ 944.9 μg·L −1 in 3 h, respectively. X‐ray diffraction (XRD), energy dispersive spectroscopy (EDS), and inductively coupled plasma (ICP) characterizations on the Mg‐CaCO 3 LSs before and after adsorbing Pb(II) confirm that the high removal performance could be ascribed to fast metal ion exchange and excellent physical adsorption contributed by high‐index planes. The density functional theory (DFT) calculations also confirm that the much‐enhanced adsorption kinetics benefits from the optimal adsorption of the () planes. This work will provide a feasible route to design high‐efficient low‐cost adsorbents through crystal‐plane engineering.

Topics & Concepts