3.1.4. EDX Spectroscopy

EDX study is very important to analyze elemental composition of materials. Figure 4 shows the EDX spectra of Fe3O4, PANI, and PANI/Fe3O4 composites before and after adsorption of BB3 dye, respectively. The highest percentages of Fe and O is present in Fe3O4, which are 53.23 and 46.77 by weight, respectively (Figure 4a). Elsewhere, Fe and O contents were reported to be 41.6 and 41.56% [69]. After BB3 adsorption, Fe content was decreased to 40.44%, while O was increased to 53.18%. The increase in oxygen and appearance of carbon in the EDX spectrum (Figure 4b) are evidence of the adsorption of dye onto Fe3O4.

**Figure 4.** EDX of Fe3O4, PANI, and PANI/ Fe3O4 before (**<sup>a</sup>**,**c**,**<sup>e</sup>**) and after (**b**,**d**,**f**) adsorption of BB3.

The presence of C and N in the EDX spectra of PANI and PANI/ Fe3O4 composites indicates their formation. The weight percentages of C and N are 64.35 and 17.04 in PANI, respectively. Besides C and N, some other elements, such as Fe, O, S, and Cl, are also present in PANI texture. Their presence is attributed to the contribution from FeCl3 and DBSA, which were used as oxidant and emulsifying agents, respectively. The increase in the percentage weights of C and O indicates adsorption of BB3 on PANI, shown in Figure 4d. Figure 4e shows the EDX spectrum of the PANI/Fe3O4 composite. It contains 41.76 and 1.45% C and N, respectively, in addition to 13.27% Fe, indicating formation of the PANI/Fe3O4 composite. Like PANI, PANI/Fe3O4 composites also contain 2.66% S due to DBSA. In the EDX spectrum of the composite, the contents of both C and O increase after interaction with BB3 (Figure 4f), which suggests the adsorption of BB3 on the composite [70]. These observations support the results obtained through UV-Vis and FTIR spectroscopies.
