Removal of chemical oxygen demand from agro effluent by ZnO photocatalysis and photo‑Fenton

Wong, Soon Pang and Yahya, Marvis Sakai (2019) Removal of chemical oxygen demand from agro effluent by ZnO photocatalysis and photo‑Fenton. SN Applied Sciences, 1. p. 738. ISSN 2523-3963

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Abstract

The direct discharge of improperly treated effluent from sago industry poses a great threat to water bodies due to the high amount of organic matter. This work investigated ZnO photocatalytic degradation under aerated and non-aerated conditions, and photo-Fenton aiming to reduce the chemical oxygen demand in sago effluent. Photolysis of sago effluent in the presence of ultraviolet irradiation and aeration resulted in 68% of the chemical oxygen demand removal. The results indicate high chemical oxygen demand reductions for different concentrations of sago effluent at 1:10, 1:100, and 1:1000 diluted with distilled water following the ZnO photocatalytic treatment under the aerated conditions. The chemical oxygen demand reductions of 90–95% and 85% were obtained using 3 g/L of ZnO, after 2 h of aerated and nonaerated photocatalytic treatments, respectively, for the sago effluent ratio of 1:1000. On the other hand, the combination of the most concentrated sago effluent at 1:10 and non-aerated ZnO photocatalytic treatment resulted in no appreciable chemical oxygen demand reduction at only 8%. The concentrations of Fe2+ (10–60 mM) and H2O2 (50–150 mM) greatly influenced the degradation rates of chemical oxygen demand. The optimum parameters of 10 mM of Fe2+ and 50 mM of H2O2 were able to reduce 97% of the chemical oxygen demand of the 1:1000 sago effluent under the photo-Fenton treatment with 2 h of ultraviolet irradiation. Thus, both ZnO photocatalysis and photo-Fenton can be applied as the possible treatment methods to reduce the chemical oxygen demand in effluent from sago processing

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