## 3 Results and Discussion
### Adsorption Removal Efficiency Study  
The adsorption experiments were carried out in order to determine the removal efficiency of adsorbents at the equilibirum time for the target dyes. Experiments were performed with a fixed amount of adsorbent (5 mg) at different initial concentrations of synthetic dyes ranging from 4 to 100 mg/L, under slow mixing conditions (50 rpm). As shown in Figure 5, the findings indicated that as the dye concentration increased, the removal efficiency of adsorbents decreased. GO was observed to achieve the highest removal efficiency of 99.9% at a 4 mg/L MB concentration after 11 days (Figure 5a). Overall, the comparison of the removal efficiency of GO and GAC indicated that as the MB concentration increased, GO and GAC exhibited similar removal efficiencies; however, it is important to note that the required adsorption times were quite different, with 11 days for GO and 31 days for GAC (Figure 3) NaY was the least efficient compared to GO and GAC; for instance, with a dye concentration of 4 mg/L MB, only 46.2% removal was achieved. These findings highlight the higher removal efficiency with a shorter removal time of GO compared to GAC and NaY in the removal of MB as a cationic synthetic dye under slow mixing conditions, which is attributed to GO's higher oxygen functional groups and porous structure.  
\begin{table}
\begin{tabular}{c c c c c} \hline \multicolumn{5}{c}{**Kinetic Parameters for Adsorption with RhB**} \\ \hline
**Kinetic Model** & **Parameters** & \multicolumn{3}{c}{**Adsorbents**} \\ \hline  & & **GO** & **GAC** & **NaY** \\ \hline \multirow{4}{*}{Pseudo-first-order} & q\({}_{\text{e}}\) (mg/g) & 62.2 & 64.2 & 7.3 \\ \cline{2-5}  & q\({}_{\text{m}}\) (mg/g) & 60.25 & 60.2 & 15.4 \\ \cline{2-5}  & K\({}_{1}\) (min\({}^{-1}\)) & 0.01 & 0.01 & 0.04 \\ \cline{2-5}  & R\({}^{2}\) & 0.928 & 0.829 & 0.554 \\ \hline \multirow{4}{*}{Pseudo-second-order} & q\({}_{\text{m}}\) & 76.9 & 68.9 & 4.8 \\ \cline{2-5}  & K\({}_{2}\) (g/mg.min) & 0.0001 & 0.0003 & 0.01 \\ \cline{2-5}  & R\({}^{2}\) & 0.987 & 0.976 & 0.917 \\ \hline \multirow{4}{*}{Elovich} & \(\beta\) (g/mg) & 10.98 & 11.2 & 0.918 \\ \cline{2-5}  & \(\alpha\) (mg/g.min) & \(-4.06\) & \(-4.8\) & 0.08 \\ \cline{2-5}  & R\({}^{2}\) & 0.964 & 0.963 & 0.485 \\ \hline \multirow{4}{*}{Intraparticle diffusion} & K\({}_{\text{1d}}\) (mg/g.h\({}^{1/2}\)) & 3.20 & 4.76 & 0.562 \\ \cline{2-5}  & C\({}_{1}\) (mg/g) & 9.23 & 1.10 & 0.03 \\ \cline{2-5}  & R\({}^{2}\) & 0.947 & 0.993 & 0.663 \\ \cline{2-5}  & K\({}_{\text{2d}}\) (mg/g.h\({}^{1/2}\)) & - & 2.64 & - \\ \cline{2-5}  & C\({}_{2}\) (mg/g) & - & 20.2 & - \\ \cline{2-5}  & R\({}^{2}\) & - & 0.819 & - \\ \cline{2-5}  & K\({}_{\text{3d}}\) (mg/g.h\({}^{1/2}\)) & - & 1.46 & - \\ \cline{2-5}  & C\({}_{3}\) (mg/g) & - & 36.8 & - \\ \cline{2-5}  & R\({}^{2}\) & - & 0.666 & - \\ \hline \end{tabular}
\end{table}
Table 2: Summary of kinetic model parameters for removal of RhB for the adsorbents studied.  
For removal of RhB, GO achieved a significantly higher removal efficiency (86.6%) at 4 mg/L of dye concentration after 5 days, compared to GAC and NaY, with removal efficiencies of 71% and 5.5% after 31 and 3 days, respectively (Figure 5b). The low RhB removal efficiency of NaY could be attributed to a pore size limitation, which prevented larger molecules such as RB from passing through its pores. The NaY removal efficiencies could also be affected by RhB dissociation over the course of the experiment.