*3.6. EDS*

The elemental distribution of carbon, oxygen, nitrogen, mercury and chromium in hydrogel matrix was evaluated by EDS analysis and the spectra for Hg2<sup>+</sup> adsorbed GT-cl-DMA hydrogel, Hg2<sup>+</sup> adsorbed GT-cl-poly(DMA)/RGO hydrogel composite, Cr6<sup>+</sup> adsorbed GT-cl-poly(DMA) and Cr6<sup>+</sup> adsorbed GT-cl-poly(DMA)/RGO are presented in Figure 5. It is evident from the elemental analysis that Hg2<sup>+</sup> and Cr6<sup>+</sup> ions were successfully adsorbed by GT-cl-poly(DMA) and GT-cl-poly(DMA)/RGO. Importantly, the weight percentages of Hg2<sup>+</sup> and Cr6<sup>+</sup> ions were higher in the case of Hg2<sup>+</sup> adsorbed GT-cl-poly(DMA)/RGO (6.68%) (Figure 5b) and Cr6<sup>+</sup> adsorbed GT-cl-poly(DMA)/RGO (0.86%) (Figure 5d) than the Hg2<sup>+</sup> adsorbed GT-cl-poly(DMA) (1.20%) (Figure 5a) and Cr6<sup>+</sup> adsorbed GT-cl-poly(DMA) (0.46%) respectively (Figure 5c). Hence, GT-cl-poly(DMA)/RGO hydrogel composite showed better adsorption capability than GT-cl-poly(DMA) hydrogel. Also, the weight percentage of carbon is higher the in case of GT-cl-poly(DMA)/RGO hydrogel composite than the GT-cl-poly(DMA) hydrogel which confirmed the successful dispersion of RGO in GT-cl-poly(DMA) hydrogel matrix.

**Figure 4.** Scanning electron microscope images of (**a**) RGO, (**b**) gum tragacanth-cl-*N,N*dimethylacrylamide hydrogel and (**c**) reduced graphene oxide incorporated gum tragacanth-cl-*N,N*-dimethylacrylamide hydrogel composite.

**Figure 5.** Energy dispersive X-ray spectroscopy and elemental weight percentage for (**a**) Hg2<sup>+</sup> adsorbed gum tragacanth-cl-*N,N*-dimethylacrylamide (GT-cl-poly(DMA)) hydrogel, (**b**) Hg2<sup>+</sup> adsorbed reduced graphene oxide incorporated gum tragacanth-cl-*N,N*-dimethylacrylamide (GT-cl-poly(DMA)/RGO) hydrogel composite, (**c**) Cr6<sup>+</sup> adsorbed gum tragacanth-cl-*N,N*-dimethylacrylamide (GT-clpoly(DMA)) hydrogel and (**d**) Cr6<sup>+</sup> adsorbed reduced graphene oxide incorporated gum tragacanth-cl-*N,N*-dimethylacrylamide (GT-cl-poly(DMA)/RGO) hydrogel composite.

*3.7. Application of Gum Tragacanth-cl-N,N-dimethylacrylamide (GT-cl-poly(DMA)) Hydrogel and Reduced Graphene Oxide Incorporated Gum Tragacanth-cl-N,N-dimethylacrylamide (GT-cl-poly(DMA)*/*RGO) Hydrogel Composite for Removal of Hg2*<sup>+</sup> *and Cr6*<sup>+</sup>
