Synthesis and characterization of zeolite A by hydrothermal transformation of natural Jordanian kaolin

Peer review under responsibility of University of Bahrain.

Figures & data

Table 1 Properties of natural Jordanian kaolin.

Chemical constituents in wt.% [X-ray fluorescence analysis (XRF)]
SiO2	53.86
TiO2	0.74
Al2O3	32.45
Fe2O3	0.65
MnO	0.01
MgO	0.08
CaO	0.13
Na2O	0.06
K2O	0.54
P2O5	0.12
Loss on ignition (LOI)	11.21
Total	99.85
SiO2/Al2O3 ratio	1.65
Particle size distribution in wt.% [Atterberg method]
Microns 63–45 μm	1.2
Microns −45+6 μm	5.2
Microns −6+2 μm	20.6
Microns −2 μm	73.0
Quantitative analysis in wt.% [using XRD (Rietveld method with DIFFRACplus TOPAS software) + XRF]
Kaolin	72.0
Quartz	27.0
Others	1 .0
Brightness (% ISO)	82.73

Figure 1 XRD patterns of Jordanian kaolin (a) and metakaolin at 650 °C (b).

Table 2 Phase composition of the obtained zeolite products (wt.%) was performed using the Rietveld method with DIFFRAC_plus TOPAS software.

NaOH(M)	Quartz	Hydroxysodalite (HS)	Zeolite A	Metakaolin (amorphous)	Total
1.0	30.2	0.0	39.7	30.1	100.0
1.5	25.6	4.2	70.2	0.0	100.0
2.0	24.3	3.8	71.9	0.0	100.0
2.5	18.0	7.8	74.2	0.0	100.0
3.0	16.9	8.5	74.6	0.0	100.0
3.5	16.3	15.4	68.2	0.0	100.0
4.0	15.4	33.8	50.8	0.0	100.0

Figure 2 XRD patterns of zeolite A and associated phases obtained by hydrothermal synthesis (a) unreacted metakaolin, (b) 1.0 M NaOH, (c) 1.5 M NaOH, (d) 2.0 M NaOH, (e) 2.5 M NaOH, (f) 3.0 M NaOH, (g) 3.5 M NaOH, and (h) 4.0 M NaOH, (i) commercial zeolite A. A: zeolite A, S: hydroxysodalite, Qz: quartz.

Figure 3 FTIR spectra of zeolite A and associated phases obtained by hydrothermal synthesis: (a) unreacted metakaolin, (b) 1.0 M NaOH, (c) 1.5 M NaOH, (d) 2.0 M NaOH, (e) 2.5 M NaOH, (f) 3.0 M NaOH, (g) 3.5 M NaOH, (h) 4.0 M NaOH, and (i) commercial zeolite A (Fluka No. 69836).

Figure 4 SEM micrographs showing the occurrence of zeolite A and associated phases obtained by hydrothermal synthesis: (a) hexagonal platy crystals of untreated kaolin, (b) very well developed cubes of zeolite A and relicts of metakaolin, (c) zeolite A probably formed before hydroxysodalite (HS), as shown by the occurrence of HS crystals growing at the surface of zeolite A. (d–f) Spheroidal aggregates of HS that grew out onto the surface of cubic crystals of zeolite A, showing penetration twining, and (g–h) lephispheric morphology of HS associated to cubic crystals of zeolite.