In this study, TiO2 was modified and immobilized on polypropylene (PP) granules to prepare buoyant photocatalyst with visible light activity. The TiO2 nano-sol was first prepared from titanium n-butoxide (Ti(OBu)(4)) in the presence of acetyl acetone (AcAc) or acetic acid (AcOH) as an inhibiting agent and subsequently treated with triethylamine (TEA) under the condition of room temperature. Then, a simple one-step process was utilized for the simultaneous crystallization and immobilization of the treated TiO2 nanoparticles on the PP substrate in a low temperature hydrothermal reactor (150 degrees C). It was found that the TEA-treated TiO2 nano-sol with AcAc as the inhibiting agent led to high visible light activity for the prepared photocatalyst from the low temperature hydrothermal process. The light absorption edge was up to 800 nm, and the visible light absorption rate reached 32 to 66%, depending on the TEA-treatment time. XRD analysis showed all the TiO2-based photocatalysts having the major crystal structure of anatase and minor of brookite. Raman spectroscopy, however, clearly revealed the existence of the nitrogen-doped composition (i.e., TiO2-xNx) in the photocatalyst with high visible light activity. Experiments conducted for decolorization of methyl orange (MO) dye solutions showed the effectiveness of the prepared novel photocatalyst under both the UV and the visible light.