Kinetic studies of BOD5, COD and Chromium removal in tannery effluent using ZnO-ZnFe2O4 composite photocatalyst supported on activated carbon

Haji Mohammed A*, Hamza A, Waz

Abstract

The kinetics studies of the adsorption and degradation phenomena involving tanning wastewater containing high BOD5, COD and chromium were investigated using a batch reactor and UV light irradiation under ambient conditions of temperature and pressure. Experiments were performed in a suspended ZnO-ZnFe2O4/20g AC system at natural pH of 6.93 and catalyst concentration of 0.1 mg/100ml. The initial concentration of tannery wastewater was varied between 0.1mg/10ml- 0.1mg/100ml. The kinetic analysis of the photodecomposition of tannery wastewater showed that the disappearance followed satisfactorily the pseudo first-order according to Langmuir— Hinshelwood model. The plots obtain from this model were then used to determine the values of ro, 1/Co and 1/ro. The photocatalytic removal of BOD5, COD and Cr nicely fitted the Langmuir – Hinshelwood kinetic model (R2 = 0.9364 for BOD5, 0.9673 for COD, and 1 for Cr). The adsorption of the three parameters was found to be the rate controlling step of the photocatalytic processes.

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