MnO2 AND MnO2/TiO2 MEDIATED, PERSULPHATE ENHANCED PHOTOCATALYSIS FOR THE REMOVAL OF INDIGO CARMINE DYE POLLUTANT FROM WATER

K P Vidya Lekshmi,Suguna Yesodharan,E P Yesodharan

doi:10.17628/ecb.2017.6.177-191

K P Vidya Lekshmi, Suguna Yesodharan + Show 1 more

Open Access

https://doi.org/10.17628/ecb.2017.6.177-191

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Abstract

MnO 2 and its combination (MnO 2 /TiO 2 ) are examined as potential photocatalysts for the removal of Indigo Carmine (IC) dye pollutant from water. The catalysts are characterized by XRD, FTIR, SEM, TEM, adsorption and surface area measurements. While MnO 2 is very efficient for the decolorization of the dye, it is not effective enough for mineralization. MnO 2 /TiO 2 as the photocatalyst at the optimized ratio of 9:1 combines the advantages of both the oxides, i.e., rapid decolorization and efficient mineralization. Persulphate (S 2 O 8 2- ) enhances the degradation while H 2 O 2 inhibits the same. The degradation is dependent on pH with higher degradation under extreme acidic conditions. The influence of dissolved salts/anions in water on the degradation varies from ‘moderate inhibition’ to ‘no effect’ or even ‘enhancement’ depending on the chemistry of the anion and reaction conditions. Effect of various parameters such as reaction time, substrate concentration, catalyst dosage, presence of O 2, recycling of the catalyst etc. on the efficiency of degradation is investigated. The results are critically analyzed and a tentative mechanism is proposed.

Highlights

Heterogeneous photocatalysis mediated by semiconductor (SC) oxides is an efficient advanced oxidation process (AOP) for the decontamination of water from chemical and bacterial pollutants.[1,2,3,4,5] When the SC oxide is irradiated with a light energy source (UV or visible) such that hν > Eg, electron-hole pairs are created
Scanning Electron Microscopy (SEM) measurements were performed with JEOL Model JSM-6390LV
Trace amounts of the toxic dye pollutant Indigo Carmine in water are degraded efficiently by MnO2 mediated photocatalysis

Summary

Introduction

Heterogeneous photocatalysis mediated by semiconductor (SC) oxides is an efficient advanced oxidation process (AOP) for the decontamination of water from chemical and bacterial pollutants.[1,2,3,4,5] When the SC oxide is irradiated with a light energy source (UV or visible) such that hν > Eg (band gap of the SC), electron-hole pairs are created. The rate of degradation is: The photocatalytic degradation of many organic pollutants in water is reported to follow pseudo first order kinetics.[35,36,37] The increase in degradation with an increase in concentration up to 40 mg L-1may is due to increase in adsorption of IC on MnO2 which will continue until the surface is fully covered and all the active sites are occupied.

Results

Conclusion