Three types of binder PVA, PVC and PVA/PVC mixtures have been evaluated for PANi-TiO2 immobilized system. These binders have been varied to several weights of loading for optimization purposes. As a result, it shows that higher loading of binders improved the photodegradation of RR4 dye but the mechanical properties of each immobilized system started to decreases. This behavior occurs due to the immobilized particles coated on the plate easy to peel off despite weak attachment toward to the continuous photodegradation operation system. Therefore 4 times of dipping PVA and PVC layers was selected as the optimum loading of binders to the PANi/TiO2 system during photocatalytic degradation of Reactive Red 4 with the rate constant of 0.5568 K/min for PVA and 0.5742 K/min for PVC. Meanwhile for PVA/PVC mixture binder system at 4 times dipping showed the highest rate constant of photodegradation of RR4 dye with 0.6026 K/min. In addition, SEM analysis has also been carried out for further investigation.
Modification has been made to TiO2 thin film to improve the wettability and the absorption of light. The sol-gel spin coating method was successfully used to synthesize GO/TiO2 thin films using a titanium (IV) isopropoxide (TTIP) as a precursor. Different amounts of polyethylene glycol (PEG) (20 to 100 mg) were added into the parent sol solution to improve the optical properties and wettability of the GO/TiO2 thin film. The effect of different amounts of PEG was characterized using X-ray diffraction (XRD) for the phase composition, scanning electron microscopy (SEM) for microstructure observation, atomic force microscopy (AFM) for the surface topography, ultraviolet-visible spectrophotometry (UV-VIS) for the optical properties and wettability of the thin films by measuring the water contact angle. The XRD analysis showed the amorphous phase. The SEM and AFM images revealed that the particles were less agglomerated and surface roughness increases from 1.21 × 102 to 2.63 × 102 nm when the amount of PEG increased. The wettability analysis results show that the water contact angle of the thin film decreased to 27.52° with the increase of PEG to 80 mg which indicated that the thin film has hydrophilic properties. The optical properties also improved significantly, where the light absorbance wavelength became wider and the band gap was reduced from 3.31 to 2.82 eV with the presence of PEG.