Synthesis and characterization of zeolites 4A and Na–P1
Zeolites4 Aand Na–P1 were formed as major phases in both integrated
synthesis processes 1 and 2. Their structures were revealed
by SEM (Fig. 3) and characterized by well-defined crystalline planes
for Na–P1 in process 1 (Fig. 3A), with less defined morphology for
process 2 (Fig. 3C). Zeolite4Aexhibited typical morphology (faceted
cubes) for both processes (Fig. 3B and D). In process 1, in addition
to Na–P1, the formation of zeolite sodalite was observed via XRD
(Fig. 4A), though probably only a small amount, since it was not
detected with SEM. The diffractogram also shows the presence of
unreacted quartz and mullite, originally present in the fly ash [14].
The solubility of these minerals in NaOH and likely saturation of
the reactive medium with Si and Al explain this behavior. Zeolite
X was also identified as a contaminant of zeolite 4A (Fig. 4B). In
integrated process 2, zeolite Na–P1 was observed in the formation
phase of zeolite 4A (Fig. 4C). This result does not compromise the
quality of the zeolitic product, since zeolite Na–P1 is also used in
detergent formulation.
Table 2 shows the best results obtained by zeolitization. Zeolite
4A is produced with the same quality (CEC 4.5meqg−1) and
semi-quantitative zeolite content (82%) in both processes, indicating
that its formation can be controlled by adding a secondary Al