Microwave-induced catalytic degradation of a textile dye using bentonite–poly(o-toluidine) nanohybrid

Abstract

The present study highlights the potential use of natural clay based organic–inorganic hybrids as eco-friendly catalysts for the degradation of Malachite Green under microwave irradiation. Bentonite–poly(o-toluidine) nano hybrid was prepared through microwave-assisted solid state in situ intercalation and polymerization. The intercalation of poly(o-toluidine) was confirmed by X-ray diffraction analysis, while its conducting state was confirmed by UV-visible spectroscopy. Transmission electron microscopic studies revealed that poly(o-toluidine) extracted from the bentonite interlayer space formed nano spheres and tablets of controlled dimensions. The catalytic efficiency of the nanohybrid in degrading Malachite Green under microwave irradiation was investigated in 100 ppm dye solution in the presence of 200 mg of the catalyst for different time intervals. The degradation efficiency of the nanohybrid was observed to be as high as 95% in 10 min. Kinetic analysis demonstrated pseudo first order reaction rate with k values equal to 0.17 min⁻¹ and 0.19 min⁻¹ respectively at 300 nm and 625 nm in presence of nanohybrid catalyst. Liquid chromatography-mass spectroscopy confirmed the degradation of dye into intermediates of molar mass as low as m/z 89 and 58. TOC analysis showed 94% mineralization of the dye in 20 min in presence of nanohybrid catalyst. Thus, this nanohybrid could be used as a benign microwave catalyst for the non-toxic degradation of dyes under microwave irradiation in absence of UV-visible light source.