Ag 2 O and Fe 2 O 3 modified oxides on the photocatalytic treatment of pulp and paper wastewater.

The effects of doping of ZnO and Nb ₂ O ₅ solids with Fe ₂ O ₃ (1.4 wt%) and Ag ₂ O (1.4 wt%) on its surface and catalytic properties were investigated, as well as its photocatalytic performance on the degradation of a pulp and paper wastewater (PPW). The catalysts were characterized by XRD, SEM, photoacoustic spectroscopy (PAS), NH ₃ -TPD and textural analysis. The results obtained revealed that Fe ₂ O ₃ doping of Nb ₂ O ₅ conducted at 500 °C resulted in an increase of about 116% for S _BET while Ag ₂ O treatment exerted a decrease of 33% for S _BET of the doped adsorbents. Doping ZnO with Fe ₂ O ₃ or Ag ₂ O led to an increase of 80% for S _BET . Iron and silver doping also led to a decrease in band gap energy of at least 6%. The addition of 1.4 wt% Ag ₂ O on ZnO followed by calcination at 500 °C resulted in an increase of 11% in the value of the reaction rate constant (k _ap ) for COD reduction under UV radiation. The treatment of Nb ₂ O ₅ with 1.4 wt% Ag ₂ O increased by a factor of 2.04 the value of k _ap for the reaction taking place under VIS radiation. The catalysts partially reduced the organic load and the real colour of the wastewater, allowing the achievement of the specifications for release into rivers, so photocatalysis could be an alternative for pulp and paper wastewater final polishing.
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