Visible light photocatalytic degradation of wattle extract: effect of mixing CdWO4 over a semiconductive ZnO photocatalyst

Degradation of wattle (Acacia mearnsii) extract, a leather tanning agent which is mainly composed of polyphenolic compounds was attempted by photocatalytic degradation which is a hindrance to the conventional bio-treatment of tannery effluent. To serve the process a novel semiconductive mixed catalyst CdWO4-ZnO was prepared by a simple hydrothermal method. The degradation reaction was carried out with a visible light source in a neutral medium for three hours. The results depicted the better catalytic activity of CdWO4-ZnO (band gap 2.8 eV) in degrading the organics when compared to undoped ZnO (band gap 3.8 eV) under visible light. The results also showed that the catalyst is appropriate at 36.8 weight percentage of CdWO4 in ZnO. The catalyst morphological and optical characteristics, and degradation of wattle were carefully analyzed.