Study on the Efficient Removal of Methylene Blue by Coral-Like Ni/Fe Atom Clusters and Their Adsorption Mechanism

Graphical The Ni 3 Fe 1 -BC composite, featuring a coral-like mesoporous architecture and exposed Ni 2+ /Fe 3+ active sites, facilitates the rapid, monolayer adsorption of methyl blue through strong Ni─O coordination. The process follows Langmuir isotherm and pseudo-second-order kinetics, indicating high affinity and thermodynamic spontaneity. In this paper, the coral-like structure of Ni/Fe bimetallic atom cluster composite adsorbent (Ni 3 Fe 1 -BC) was utilized for the efficient removal of methyl blue (MB), and a removal rate of 98% could be achieved within 25 min. The large specific surface area and mesoporous structure of the material provide effective channels for the diffusion and adsorption of MB molecules. Ni 2+ and Fe 3+ species act as key adsorption sites during the adsorption process, especially when the oxygen atoms in MB first interact with Ni atoms to form a stable chemical bond, which enhances the stability of adsorption. Meanwhile, the adsorption process conformed to the pseudo-secondary kinetic model, and the isotherm analysis showed that the Langmuir model fitted better, reflecting the monolayer adsorption characteristics. The adsorption energy E ads = −2.04 eV further proved that the adsorption process was spontaneous and exothermic with good thermodynamic stability. In addition, Ni 3 Fe 1 -BC exhibits excellent adaptability and cyclic stability in different water environments, making it an efficient and stable adsorbent for water treatment.