DOI: https://doi.org/10.55373/mjchem.v26i6.174

Keywords: Immobilized TiO₂; reverse method; photocatalytic degradation; ENR/PVC immobilization

Abstract

Immobilized Ag/TiO₂ was prepared using reverse (R) and normal (N) methods, employing epoxidized natural rubber (ENR-50) and polyvinyl chloride (PVC) as polymer binders to form a Ag-TiO₂/ENR/PVC (ATEP(R)) plate in order to address the solvent interference issue. The immobilization of TiO₂ was performed prior to the photodeposition of Ag (50, 100 and 400 ppm), by irradiation with a 250-Watt metal halide lamp for 90 minutes. TiO₂ was coated onto glass plates using a dip-coating technique. Methylene blue (MB) was employed as a model pollutant to evaluate the photocatalytic activity of the prepared immobilized Ag/TiO₂. Several instruments were used for characterization, including Ultraviolet-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS), Fourier Transform Infrared spectroscopy (FTIR) and photoelectrochemical (PEC) analysis. The UV-Vis DRS results indicated that the band gap for 100 ppm of Ag-TiO₂/ENR/PVC (100-ATEP(R)) was 2.42 eV, with its absorption edge shifted towards the visible region. FTIR analysis showed a peak at 1382 cm-1, confirming the successful doping of Ag onto TiO₂, while a less intense peak for OH at 3400 cm-1 indicated the low hydrophilicity of the photocatalyst. PEC analysis revealed that 100-ATEP(R) exhibited higher current density in linear sweep voltammetry (LSV) curves, lower charge transfer resistance in Nyquist plots and higher photocurrent response in chronoamperometry (CA) plots, compared to TiO₂/ENR/PVC (reverse) TEP(R). All immobilized ATEP(R) samples showed excellent photocatalytic degradation of methylene blue (MB) dye and achieved 52 % decolorization within 1 hour of light irradiation, indicating higher photocatalytic activity compared to the normal method. The photocatalytic degradation of all samples followed the pseudo-first-order reaction model of Langmuir Hinshelwood, with R2 values above 0.90. The results indicate that this new immobilization method may be used for all photocatalysts as it can prevent disruption of the immobilized photocatalyst by the solvent, which is a disadvantage of the normal immobilization method.