## 3 Results and Discussion  
### Characterization  
The characterization techniques in this study evaluated differences in adsorbent structures. The SEM surface morphology analysis compared adsorbent surfaces and indicated surface changes for adsorbents before and after MB and RhB adsorption (Figure 1). The pristine, highly porous GAC structures with sharp edges are shown in Figure 1a. Those sharp edges were smoothened by adsorption of dyes and coating with MB and RhB (Figure 1b,c). The crystalline and cubical structure of pristine NaY are shown in Figure 1d. Adsorption of MB caused a considerable change in the edges that could suggest interaction between oxygen located in the edges and MB molecules (Figure 1e). However, small differences were observed in NaY structure after adsorption of RhB in (Figure 1f). The layered structure of GO is shown in Figure 1g. The higher magnification of SEM images indicated smoothened edges and higher spacing between layers of GO after adsorption of MB (Figure 1h) due to the interaction of GO functional groups such as carboxyl and hydroxyl on the edges with MB. Similar surface changes were observed in the SEM image of GO after RhB adsorption (Figure 1i), indicating coverage of the GO surface with RhB molecules. The XRD patterns of GAC demonstrated a peak at 20 = 24\({}^{\circ}\) that corresponded to the presence of carbon (Figure 2a). Additionally, sharp peaks at 20 = 24\({}^{\circ}\) and 43\({}^{\circ}\) confirmed the presence of crystalline graphite in the structure of GAC. These peaks corresponded to the diffraction of (002) and (100), with layer spacing (d-spacing) of 0.31 and 0.21 nm, respectively. The XRD pattern of synthesized GO indicated a single peak at 20 = 10\({}^{\circ}\), confirming the presence of oxygen-containing functional groups (Figure 2b). The layer spacing of synthesized GO was calculated at 0.87 nm. The spacing between GO layers could facilitate the attraction of dye molecules into the layers. The second smaller peak at 20 = 19.3\({}^{\circ}\) corresponded to the excess graphite in the material that was not oxidized during the synthesis process, as can be seen in (Figure 2b) [7]. The NaY XRD pattern demonstrated peaks at 6\({}^{\circ}\), 10\({}^{\circ}\), 12.2\({}^{\circ}\), 16\({}^{\circ}\), 19.1\({}^{\circ}\), 20.7\({}^{\circ}\), 23.3\({}^{\circ}\), 24.1\({}^{\circ}\), 27.6\({}^{\circ}\), 31\({}^{\circ}\), 32\({}^{\circ}\), and 34.8\({}^{\circ}\) (Figure 2c)  
Figure 1: SEM images of (**a**) pristine GAC, (**b**) GAC with MB, (**c**) GAC with RhB, (**d**) pristine NaY, (**e**) NaY with MB, (**f**) NaY with RhB, (**g**) pristine GO, (**h**) GO with MB, (**i**) GO with RhB. indicating the crystalline structure of NaY. These peaks corresponded to the diffraction of (111), (220), (311), (222), (222), (440), (553), (642), (822), (555), and (840), respectively. The FT-IR analysis for all three adsorbents is indicated in Figure 2d. NaY is presented in the first plot; peaks at 3425 and 1630 cm\({}^{-1}\) are attributed to O-H bands and zeolitic water. The Si-O stretching vibration band was observed at 1019 cm\({}^{-1}\); the peak at 1111 cm\({}^{-1}\) may represent the presence of Al-O-Al or Si-O-Si. Peaks at 792 and 459 cm\({}^{-1}\) are attributed to quartz or amorphous SiO\({}_{2}\) stretching vibration and Si-O-Si bending mode [23; 26]. The spectrum of GAC indicated peaks at 2960 and 2928 cm\({}^{-1}\) that are associated with symmetric and asymmetric stretching vibrations of CH\({}_{2}\) bonds. The peak at 1721 cm\({}^{-1}\) may represent C=O stretching vibration and 1384 and 1272 cm\({}^{-1}\) peaks are attributed to C-OH stretching vibrations [27]. The FT-IR spectrum of GO revealed a broad and strong peak at 3379 cm\({}^{-1}\) that was attributed to the vibrational bonds of O-H (Figure 2d) and peaks in 1739 and 1420 cm\({}^{-1}\) confirmed the presence of carboxyl groups (carboxylic acid) with stretching bonds of C=O. The presence of sharper and broader peaks in GO compared to GAC suggested a higher volume of oxygen-containing functional groups on its surface [7].