# Immobilized TiO\({}_{2}\)-Polyethylene Glycol: Effects of Aeration and pH of Methylene Blue Dye
## 2 Experimental
### The Washing Process of Immobilized Samples and Photoactivity Test under Different Light Conditions  
The cleaning process was conducted to remove all unwanted contaminants by irradiating the immobilized samples using distilled water. The washing process was carried out for one hour under normal light (NL) irradiation to increase the permeability performance prior to photoactivity test. The photoactivities of the immobilized samples were tested by degradation of methylene blue (MB; Fluka Analytical, St. Louis, MO, USA). The experimental setup used was to apply immobilizedsample with 20 mL of 12 mg/L concentration of MB dye into a glass cell (dimension: 50 mm length \(\times\) 10 mm width \(\times\) 80 mm height). An NS 7200 aquarium pump was used as an aeration source along the photodegradation process. Area of photocatalytic activity is equal to length \(\times\) width of DSAT applied, which is 6.6 cm \(\times\) 4.6 cm. The photoactivity tests of the immobilized samples were conducted under normal light and visible light (VL) irradiation. The NL intensity of the lamp used was measured at about 461 and 6.7 W/m\({}^{2}\) for visible and UV lights, respectively, while an intensity of 430 W/m\({}^{2}\) was used for VL source. Turning on the 55-W compact fluorescent lamp as the normal light source as shown in Figure 1 initiated the photocatalytic reaction, and outlet absorbance was measured. A 4 mL aliquot was extracted from the glass cell reactor at pre-specified intervals. The absorbance of the aliquot was measured by a UV spectrophotometer (Varian UV-Vis detector model HACH DR 1900, HACH, Loveland, CO, USA) set to 661 nm, which corresponds to the MB absorbance. MB concentration trends were simulated using a pseudo first-order rate constant plot of \(\ln(C_{o}/C_{t})=kt\), where \(Co\) represents the MB concentration at \(t\) = 0 min, \(C_{t}\) is the concentration at time \(t\), and \(k\) is kinetic constant or photoactivity efficiency at min\({}^{-1}\). The concentration of MB at different experimental times was spectrometrically evaluated [28]. The final MB concentration can be spectrometrically determined with a calibration curve using the Beer-Lambert equation, which is \(A=l\varepsilon\)[MB], where \(l\) is the path length, [MB] is the concentration of the dye, and \(\varepsilon\) is the MB molar absorptivity [27]. For VL irradiation, a glass cell that contained MB solutions was exposed to the visible light from a 55-W fluorescent lamp attached with a UV filter (>420 nm) at room temperature conditions. With the pseudo first-order plot, absorbance was converted to concentration, and rate of degradation (\(k\)) was calculated.  
Characterization of Immobilized Samples Using Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS)  
FT-IR spectra of immobilized TiO\({}_{2}\) and TiO\({}_{2}\)/PEG samples in powder form were analysed on Perkin Elmer Spectrum Version equipped with an attenuated total reflectance device (Frontier, Waltham, MA, USA) with a diamond crystal. Spectra were collected in a wavelength range of 600-4000 cm\({}^{-1}\) with four scans and spectral resolution of 4 cm\({}^{-1}\). The binding energy of immobilized TiO\({}_{2}\)/PEG was determined using X-ray photoelectron spectroscopy (XPS) with a Thermo ESCALAB 250 spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) using a radiation source of monochromatic Al K\(\alpha\) with the energy of 1486.6 eV.