DOI: https://doi.org/10.55373/mjchem.v26i2.12

Keywords: Dissolved oxygen; RR4 dye; silver; titanium dioxide; wastewater

Abstract

This study proposed to enhance the photocatalytic performance of Ag-TiO2 by manipulating Ag0 and Ag+ formation on TiO2 through controlled dissolved oxygen (DO) levels by photo- deposition of Ag (1-5 wt.%) to TiO2 under N2 gas purging (0-60 min; denoted as DO0-DO60). The photocatalytic performance of the immobilised Ag-TiO2 was determined under the photodegradation of Reactive Red 4 (RR4) dye. XRD and FTIR revealed the existence of Ag+ and Ag0, corresponding to Ag2O and Ag-TiO2, respectively. The HRTEM images showed a spheroid shape of Ag-TiO2 with 0.20 and 0.24 nm of d-spacing, representing Ag metal and Ag2O, respectively. The lower PL intensity of Ag-TiO2 suggested a reduced e-/h+ recombination rate, while UV-Vis/DRS analysis indicated strong visible light absorption due to the surface plasmonic resonance (SPR) effect. This study proves that Ag2O can increase photocatalytic performance as an electron injector to Ag-TiO2, however, excess formation of Ag2O can retard the photocatalytic activity. Optimal 3 wt.% Ag doping at 30 min N 2 purging (3AT-DO30) achieved complete 30 mg L-1 RR4 dye degradation in 1 hour, surpassing unmodified TiO2 by 63.1%. The photocatalytic performance order was TiO2 < 3AT-DO60 < 3AT-DO0 < 3AT-DO10 < 3AT-DO30, with all samples maintaining stability over 10 cycles.