Influence of physical/chemical treatments to delamination of nanohybrid kaolinite-dipicolinate

• Kaolinite-dipicolinate complex was delaminated.
• All the methods and solvents employed herein give similar results.
• The properties and chemical stability of the materials obtained were investigated.
• Grafted dipicolinic acid molecules are not leached from kaolinite matrix.

This work shows how submitting kaolinite grafted with dipicolinic acid (Kaol-dpa) to treatment with different solvents and physical/chemical treatment (e.g., ultrasound bath, magnetic stirring, or thermal treatment in water) influences Ka-dpa delamination. X-ray powder diffraction, chemical analysis (C, H, and N), thermal analysis, Fourier-transform infrared spectroscopy, and transmission electron microscopy aided examination of all the samples. Delamination of the treated Kaol-dpa samples elicited changes in the intensity of the characteristic Kaol-dpa d001 reflections. Treatment with different solvents reduced the intensity of the d001 reflections, which almost disappeared for the sample treated with water suggesting the exfoliation. Ultrasound bath, thermal treatment, and magnetic stirring in water also decreased the typical Kaol-dpa d001 reflection and increased the reflection at 2θ = 12.2°, the reflection due to the basal spacing of purified kaolinite. Long treatment times eliminated the dipicolinic acid that was only adsorbed onto Kaol-dpa nanohybrid. In conclusion, different types of physical treatment in water were able to delaminate Kaol-dpa, thereby exposing the reactive pyridine-carboxylic groups present in the hybrid matrix.

Figure optionsDownload as PowerPoint slide