## 2 Results and Discussion  
### Characterization of Immobilized TiO\({}_{2}\)  
A method for immobilizing TiO\({}_{2}\) using DSAT was thoroughly described in the previous article [40]. In this work, a similar approach was taken where TiO\({}_{2}\) was coated onto DSAT as a support binder, but in the presence of a specific amount of PEG. Table 1 shows the experimental condition and pseudo first order rate constant of immobilized TiO\({}_{2}\) and the pristine TiO\({}_{2}\) sample in degrading methylene blue (MB) dye. As can be seen in Table 1, the increased amount of PEG in the formulation solutions has shown a significant increase of PEG in immobilized TiO\({}_{2}\)-PEG samples detected by FTIR analysis. The 1160- and 2900-nm peaks of C-O and C-H stretching, respectively, as shown in Figure 1, corresponded to the PEG peaks based on similar peaks presented on the FTIR spectrum for pure PEG studied by [PERSON] et al. [41]. Photocatalytic activity of washed immobilized TiO\({}_{2}\)-PEG was increased by increasing the amount of PEG from 0.05 to 0.1 g based on its photodegradation rate values. Photocatalytic activity starts to decrease beyond 0.1 g of PEG due to the agglomeration of PEG in TiO\({}_{2}\) particles, which makes it harder for a large amount of light to penetrate through the surface particles of TiO\({}_{2}\). [PERSON] et al. [39] have reported same behavior on immobilized TiO\({}_{2}\) with PVA. The catalyst loading effect of immobilized TiO\({}_{2}\) with 0.1 g of PEG samples has shown a different photocatalytic activity. Increasing the amount of catalyst loading from 0.05, 0.1, 0.2 and 0.3 grams will significantly increase the photodegradation rates from 0.039, 0.048, 0.048 and 0.087 min\({}^{-1}\), respectively. The high photodegradation rate at 0.3 g was due to the high adsorption capacity of the photocatalyst thin film composite that enhanced the decolorization process of MB dye, and eventually, this dye pollutant becomes degraded by the photocatalysis process. However, too much adsorption capacity beyond 0.3 g of catalyst loading for the immobilized TiO\({}_{2}\)-PEG sample makes the photodegradation rate become 2.5-times slower. This observation was due to the excessive adsorbed MB dye on the surface of immobilized TiO\({}_{2}\)-PEG, thus forming a thick layer coating on the TiO\({}_{2}\) surface and reducing the penetration of light for photocatalysis. It can be deduced that the immobilized TiO\({}_{2}\)-PEG ratio of 10:0.1 at a 0.3-g catalyst loading is the optimum immobilized TiO\({}_{2}\)-PEG with a photodegradation rate 1.8-times faster compared to pristine TiO\({}_{2}\); an optimum sample named as TiO\({}_{2}\)/PEG-2 (TP2) (Table 1).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**TiO\({}_{2}\)** & **Loading** & **Mode** & **Amount of** & **Ratio** & **Saret** & **Rate Constant \(k\) (min\({}^{-1}\))** \\
**Sample** & **(g)** & **(S\({}^{\text{a}}\) or I\({}^{\text{b}}\))** & **PEG (wt \%)** & **(TiO\({}_{2}\)/PEG)** & **(m\({}^{\text{a}}\)-g\({}^{\text{b}}\))** & **Washed** & **Unwashed** \\ \hline Pristine TiO\({}_{2}\) & 0.3 & S & 0.00 & 10:0 & 50.00 & 0.048 & - \\ TP0 & 0.3 & I & 0.00 & 10:0 & 49.25 & 0.054 & 0.048 \\ TP1 & 0.3 & I & 0.05 & 10:0.05 & - & 0.080 & 0.041 \\ TP2 & 0.3 & I & 0.10 & 10:0.1 & 88.30 & 0.087