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Abstract
This work reports the optimization of degradation conditions and toxicity decrease in the tannery wastewater, collected in the retanning and dyeing steps. This effluent was filtered, diluted in a 1:200 proportion, and investigated as a case study on a bench scale by heterogeneous photocatalysis. These conditions were attained when the suspension, containing 1 g L−1 of ZnO and effluent, was irradiated for 4 h at pH 8.0 and 30°C. Physico-chemical parameters such as chemical oxygen demand (COD) decreased from 15,023 to 350 mg O2 L−1; fifth-day biochemical oxygen demand (BOD5) from 4374 to 10 mg O2 L−1; total solids from 28,500 to 188 mg L−1; total organic carbon (TOC) from 4685 to 4.93 mg L−1, and turbidity from 331 to 1.15 NTU after 4 h of irradiation. The LC50 increase from 14.90% to 56.82% in the lethality assay of Artemia salina L. microcrustacean as well as the dissolved oxygen of 6.45 mg L−1 indicated efficiency in this treatment.
Acknowledgements
The authors acknowledge CNPq by the financial support, and M.C.H. is also grateful to CAPES for the scholarship.