Coupled Al-Ga-xAg composites prepared by the sol–gel method and their efficient photocatalytic performance in the degradation of diclofenac

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The photocatalytic performance of coupled Al-Ga- x Ag composites prepared by the sol-gel method (where Al: γ- Al 2 O 3 ; Ga: 1.0 wt.% Ga 2 O 3 ; and x Ag: x = 0.5, 1.0, 2.0 and 5.0 wt.% of Ag 2 O) was studied in the degradation of diclofenac in aqueous medium (50 ppm) using UV light irradiation. The structural and optical properties of Al-Ga- x Ag reveals the presence of highly dispersed Ag 0 nanoparticles and Ag + ions in the materials. The E g and the recombination rate of photo-induced electron-hole pairs of γ-Al 2 O 3 decreased by coupling 1.0 wt.% of Ga 2 O 3 and 0.5 - 5.0 wt.% of silver oxide in the coupled Al-Ga- x Ag composites. Bare γ-Al 2 O 3 photo-converts 66.0% of diclofenac after 20 min of reaction, however at this reaction time coupled Al-Ga- x Ag composites with silver oxide contents between 1.0 and 5.0 wt.%. photoconverts more than 90.0% of diclofenac and mineralizes more than 80% of dissolved total organic carbon . The diclofenac photodegradation reaction kinetics were adjusted well to a first-order Langmuir-Hinshelwood reaction kinetics. The improvement in the photocatalytic activity of coupled Al-Ga- x Ag composites could be due to that highly dispersed Ag 0 nanoparticles and Ag + ions act as electron (e − ) traps, whereas Al-Ga mixed oxide acts as hole (h + ) traps, promoting the decrease in the recombination rate of photo-induced electron-hole pairs. Transient photocurrent response experiments confirm that the silver species effectively increase efficiently the separation of photo-generated (e − , h + ) charges. Experiments of diclofenac photodegradation with addition of scavengers indicates that h + and ·O 2 − radicals are the main active species during the photocatalytic reaction using Al-Ga- x Ag composite photocatalysts . A possible diclofenac photodegradation reaction mechanism under UV light irradiation and using Al-Ga- x Ag composite photocatalysts was proposed.