Structure and Surface Properties of AI~(3+)-Modified Sepiolite

摘要

Al~(3+)-modified sepiolite was synthesized through hydrothermal treatment of acidified sepiolite using sodium aluminate as a modifier. The structure and surface properties of the modified sepiolite were characterized by XRD, FTIR, NMR, and Zeta potentials. The XRD and FTIR results demonstrated that Al~(3+) ions were introduced into the sepiolite lattice. ~(29)SiNMR of the sepiolite ore showed that Si atoms had three configurations with chemical shifts of -98.4, -95.2, and -92.5 ppm with the atomic ratio of 1.39: 1.43: 1, which was assigned to the center silicon, edge silicon, and near-edged silicon atoms, respectively. For the as-prepared Al~(3+)-modified sepiolite, the signal intensity of the edge silicon atoms decreased and shifted from -95.2 ppm to -94.5 ppm. Moreover, a new chemical shift of - 87.4ppm belonging to Q~1 structure appeared. The ratio of four configurations of silicon atoms was 1.43: 1: 1.53: 1.04. ~(27)AINMR of Al ~+-modified sepiolite showed that Al atoms have two configurations corresponding to the tetra-coordination and octahedral coordination, respectively. The results of NMR revealed that the sepiolite was modified by substitution of Si atoms in the framework and Mg atoms in the interlayer, resulting in a less negative charge on the surface of Al~(3+)-modified sepiolite.