3.1 Characterization of modified diatomite
The surface morphology and elemental analysis of OSMD and CRL were characterized by SEM (Figure 1 ). The Energy Dispersive Spectroscopy (EDS) image (Figure S1 ) showed that the OSMD surface was rich in C, S, and Fe elements, which proved the success of the surface modification. After immobilizing CRL, the proportions of S and N elements increased significantly, indicating that the support could load CRL efficiently (Figure S2 ). The OSMD still retained the original unique porous structure of diatomite after the introduction of functional groups and Fe3O4. Obviously, the surface of immobilized CRL showed a rough morphology, indicating that CRL was efficiently immobilized on the surface of the support.