Abstract

Aim: This study was aimed to to assess the effect of chemical composition (altered via acid leaching and calcination) on its photocatalytic activity using MB as the model pollutant.

Method and Materials: Visible light active photocatalyst has been synthesized by leaching of a natural sphalerite (obtained from Abuni deposit, Nasarawa, Nigeria) using oxalic acid, drying of the obtained leachate, and subsequent calcination of the dried leachate to form ZnO –α-Fe₂O_3, -ϒ- Fe₂O₃ composite with trace amounts of MoO and MnO₂ . The natural spalerite and the ZnO –α-Fe₂O_3, -ϒ- Fe₂O₃ composite photocatalyst were characterized by X – ray fluorescence, X –ray difractiomery, and UV/Vis spectroscopy. The activity of the photocatalysts was tested by monitoring the kinetics of methylene blue degradation under visible light irradiation.

Results: The photocatalytic degradation of methylene blue dye follows pseudo first order kinetics on both natural sphalerite and the ZnO –α-Fe₂O_3, -ϒ- Fe₂O₃ composite. The experimental values of the apparent rate constant for the photocatalytic degradation of methylene blue on natural sphalerite and the ZnO –α-Fe₂O_3, -ϒ- Fe₂O₃ composite were 0.009min^-1 and 0,012min ^-1 , respectively. Thus ZnO –α-Fe₂O_3, -ϒ- Fe₂O₃ composite obtained from natural sphalerite obtained from natural sphalerite can be used as a new cost effective and visible light – responsive photocatalyst.

Conclusion: It was concluded that calcined leachates are composed of ZnO α-Fe₂O_3,ϒ-Fe₂O₃ exhibited good photocatalytic property better than the leached residues and natural Sphalerite CL90 was found to be the best catalyst for the photodegradation of MB dye under visible irradiation.

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