X – ray diffraction study

Wide angle X-ray diffraction studies were performed on raw red mud and the modified red mud as shown in Fig. 9.

X - ray diffraction study

Fig. 9. Xrd pattern of (a) Raw red mud (b) Phosphomolybdic acid modified red mud (c) Organically modified red mud

The spacing, d001, of the (001) basal reflections of the Raw red mud and PRM were measured and are shown in table 7. It was found that the basal spacing of the PRM is larger than the raw red mud.

Sample

20

d-spacing (Ao)

Raw red mud

2.71

32.76

PRM

2.46

36.72

Table 7. XRD basal spacing results of raw red mud, and acid modified red mud

In the ORM, the case appears to be slightly different with the peak being lost. Thus, we could infer that the silicate layers undergo exfoliation or random dispersion at the modification stage itself. This suggests that the aniline formaldehyde type precursor have formed a coating on the partially exfoliated silicate layers leading to random dispersion thus rendering the absence of peaks in the XRD micrograph (Alexandre & Dubois, 2000).

X - ray diffraction study

Fig. 10. X-ray Diffraction pattern of (a) PVA (b) SP5 (c) CP4 (d) PRM4 film

The XRD patterns for the Virgin PVA and the PVA nanocomposite films with different critical loading percentage of modified red mud were depicted in Fig. 10. The crystallinity of the nanocomposite membranes was found to be mainly due to PVA. The characteristic diffraction peak for pure PVA was observed at 20 value of 22.56° While the diffraction peak of the nanocomposite films were considerably broadened and displaced to lower 20 values as shown in table 8, indicating reduction in the crystallinity of the nanocomposites.

The spacing, dooi, of the (001) basal reflections of the silicate galleries of the PVA nanocomposite films were measured as shown in table 3.9. It was found that the basal spacing for CP4 is larger than other nanocomposites materials, thereby giving evidence of more exfoliation in CP4 than the rest nanocomposites. Hence, it can be concluded that the interlayer spacing got increased by intercalation of polymer matrix. So, a lot of surface area of modified red mud is now available to the polymer for bonding.

Sample

20

dooi-spacing (Ao)

SP5

13.47

6.56

CP4

13.11

6.74

PRM4

19.15

4.63

Table 8. XRD d001-spacing Results

The change of crystalline behavior was further evidenced by the studies of the morphological image of as-synthesized materials. Individual silicate layers, along with two, three and four layer stacks, were found to intercalate and partially exfoliate in the PVA matrix.