COD removal and toxicity decrease from tannery wastewater by zinc oxide-assisted photocatalysis: a case study

• Published in: Environmental technology 2014-07, Vol.35 (13), p.1589-1595
• Main Authors: Hasegawa, Maria Claudia, Daniel, Juliana Feijó de Souza, Takashima, Keiko, Batista, Gisselma A, da Silva, Sandra M. C. P
• Format: Article
• Language: English
• Subjects: Animals; Applied sciences; Artemia; Artemia salina; biochemical oxygen demand; Biological Oxygen Demand Analysis; carbon; case studies; Catalysis; Catalytic reactions; Chemical engineering; chemical oxygen demand; Chemistry; COD; dissolved oxygen; dyeing; Effluents; environmental technology; Exact sciences and technology; General and physical chemistry; General purification processes; heterogeneous photocatalysis; Industrial Waste; Irradiation; Oxygen demand; Photocatalysis; Photolysis; Pollution; Reactors; Tanneries; tannery wastewater; Tanning; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; total solids; Toxicity; turbidity; Waste Disposal, Fluid - methods; Waste water; Waste Water - toxicity; wastewater; Wastewaters; Water treatment and pollution; Zinc; zinc oxide; Zinc Oxide - chemistry; ZnO
• ISSN: 1479-487X; 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2013.874499

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 O ₂ L ⁻¹; fifth-day biochemical oxygen demand (BOD ₅) from 4374 to 10 mg O ₂ 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 LC ₅₀ 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.