Synthesis and Characterization of Na-P1 (GIS) Zeolite Using Rice Husk

Abstract

This work deals with the synthesis of Na-P1 (GIS) zeolite using rice husk as the starting material, instead of the more expensive chemicals currently used in the industry (i.e., Na aluminates and Na silicates). Rice husk is calcined at the temperature of 550 °C to obtain rice husk ash. Na-P1 is synthesized starting from rice husk ash, NaOH, and NaAlO₂ by a protocol involving the mixing of a seed gel and a feedstock gel. Two synthesis runs are carried out at ambient pressure at the temperature of 110 °C by fixing the SiO₂/Al₂O₃ ratio at 3.5 and 5.3, respectively. The synthesized products have been identified as well as the experiments developed by X-ray diffraction and scanning electron microscopy. Then, the most successful synthesized powders were also characterized by infrared spectroscopy, Raman spectroscopy, specific surface area (BET), and differential thermal analysis. The cell parameters are calculated using the Rietveld method. The combined Rietveld and reference intensity ratio methods allows us to exclude the presence of impurities and residual amorphous phase in the conducted experiments. Testing rice husk as a source of amorphous silica in the synthesis of Na-P1 represents both economic and environmental advantages. The high yields and the results of the experiment open the way for the transfer to an industrial production scale.

Keywords: rice husk; synthesis; zeolite Na-P1.

Figure 1

(a) X-ray spectra of RHA. (b) IR analysis on RHA.

Figure 2

PXRD patterns of the synthesis run A (a) and B (b).

Figure 3

SEM images of Na-P1 zeolite crystals obtained at 48 h (110 °C) for experiment A (a,b).

Figure 4

SEM images of Na-P1 zeolite crystals obtained at 48 h (110 °C) for experiment B (a,b).

Figure 5

Rietveld refinement plot: observed (red +), calculated profiles (green) and difference plot (pink) for Na-P1 zeolite (110 °C-48 h) and corundum NIST 676a with tick marks at the position of the Bragg peaks. From the bottom: Na-P1 zeolite, corundum NIST 676a.

Figure 6

Nitrogen adsorption–desorption isotherms of the Na-P1 zeolite from experiment A.

Figure 7

IR spectrum of the Na-P1 (48 h at 110 °C).

Figure 8

Raman spectrum of the sample at 48 h (110 °C) of experiment A.

Figure 9

DTA-TG analysis of the sample at 48 h (110 °C) of experiment A. The asymptotic line to the x scale represents the TG analysis while the above line is related to DTA analysis.