K. B. Babitha

National Institute for Interdisciplinary Science and Technology, Tiruvananantapuram, Kerala, India

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Publications (4)7.11 Total impact

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    ABSTRACT: The removal of an organic synthetic-dye from an aqueous solution via the adsorption and decolorization processes, typically occurring in the dark-condition on the surface of semiconductor-oxides nanotubes-based adsorbents, has been demonstrated for the first time without the use of any external power-source such as the radiation, potential-difference, microwave-generator, and ultrasonicator. “Two-step” and “one-step” dye-removal methods have been developed by utilizing the hydrothermally processed hydrogen titanate (H2Ti3O7) and anatase-titania (TiO2) nanotubes in combination with the strong oxidizer such as the hydrogen peroxide (H2O2). In the “two-step” dyeremoval method, conducted in the dark-condition, the organic synthetic-dye is adsorbed from an aqueous solution on the surface of nanotubes and decolorized in another aqueous solution containing H2O2. In contrast to this, in the “one-step” dye-removal method, the simultaneous dye-adsorption and dye-decomposition (decolorization) take place in the dark-condition on the surface of nanotubes only in one aqueous solution containing H2O2. The comparison shows that the dye-removal rate-capacity in the “one-step” dye-removal method is ∼2–3 times higher relative to that in the “two-step” dye-removal method. In both the methods, the nanotubes recovered after the end of the first dye-removal cycle can be reused as catalyst for the multiple dye-removal cycles operating under the dark-condition. The underlying dye-removal mechanism is termed as “dark-catalysis” in which the presence of both the nanotubes and H2O2 has been shown to be an essential condition for the complete decolorization in the dark-condition. Due to its several benefits, the dark-catalysis mechanism appears to be a commercially viable process compared with the conventional photocatalysis mechanism.
    02/2014; 6(2):173-183. DOI:10.1166/asem.2014.1478
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    P Hareesh, K B Babitha, S Shukla
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    ABSTRACT: We report a new method for the processing of fly ash (FA) stabilized hydrogen titanate nano-sheets in the form of aggregated microspheres. The industrial silica-based FA has been utilized for this purpose which has been surface-modified by coating with the anatase-titania (TiO(2)) via sol-gel. The anatase-TiO(2) coated FA particles are subjected to the hydrothermal treatment in an autoclave under high temperature and pressure conditions in a highly alkaline solution. The hydrothermal conditions cause dissolution of silica resulting in the disintegration of other constituents of FA which are adsorbed in ionic and/or oxidized form on the surface of intermediate product of the hydrothermal treatment of anatase-TiO(2), specifically the hydrogen titanate. The adsorption of FA constituents has resulted in the stabilization of hydrogen titanate in the nano-sheet morphology instead of nanotubes. The FA stabilized hydrogen titanate nano-sheets exhibit higher specific surface-area than that of the hydrogen titanate nanotubes and have been successfully utilized for the removal of an organic synthetic-dye from an aqueous solution via surface-adsorption, involving the electrostatic-attraction and ion-exchange mechanisms operating, in the dark-condition.
    Journal of hazardous materials 06/2012; 229-230:177-82. DOI:10.1016/j.jhazmat.2012.05.093 · 4.33 Impact Factor
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    ABSTRACT: Silver (Ag) and iron (Fe) deposited nanotubes of anatase-TiO2 (ATN) have been processed via the combination of hydrothermal and ultraviolet-reduction techniques. The samples have been characterized using the scanning electron microscope, transmission electron microscope, X-ray diffraction, and ultraviolet-visible absorption spectrophotometer for determining their morphology, size, structure, and photoabsorption properties. The dye-adsorption from an aqueous solution has been investigated in the dark-condition using the pure and surface-modified ATN. The methylene blue (MB) dye has been used as a model catalytic dye-agent. It has been demonstrated that the Ag and Fe-deposition results in an enhanced dye-adsorption at equilibrium on the surface of ATN with the maximum dye-adsorption obtained for the Ag/Ti ratio of 1.0%. A model has been proposed to explain the observed differences in the variation of the amount of dye-adsorbed at equilibrium as a function of metal/Ti (M/Ti) ratio as observed for the Ag and Fe-deposition. It is concluded that the MB adsorption at equilibrium on the surface of ATN is primarily controlled by the combination of nanoparticle-size and oxygen-spill-over effects at the lowest M/Ti ratio; while for higher M/Ti ratios, it is controlled by the oxygen-spill-over effect for Ag-deposition and by the multiple-oxidation-state effect for Fe-deposition.
    Nanoscience and Nanotechnology Letters 11/2011; 3(6):809-814. DOI:10.1166/nnl.2011.1267 · 1.44 Impact Factor
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    ABSTRACT: The nanotubes of pure hydrogen titanate and anatase-titania have been synthesized via hydrothermal treatment of as-received anatase-titania particles. The formation mechanism of anatase-titania nanotubes via hydrothermal has been discussed in detail in view of the finger-prints produced by characterizing the intermediate and end products using various microscopic and spectroscopic techniques such as scanning electron microscope, high-resolution transmission electron microscope, X-ray diffraction, Brunauer, Emmett, and Teller specific surface-area measurement, Fourier transform infrared spectroscope, diffuse reflectance, photoluminescence, thermal gravimetric and differential thermal analyses. The obtained results strongly support the rollup mechanism, involving multiple nanosheets, for the formation of anatase-titania nanotubes with the formation of different intermediate hydrothermal products having various morphologies such as sodium titanate having aggregated rectangular block-like structures, hydrogen sodium titanate and pure hydrogen titanate having highly aggregated unresolved fine-structures containing nanotubes, and finally, the pure anatase-TiO2 nanotubes. It is demonstrated that, during the hydrothermal treatment, the nanotubes of pure hydrogen titanate are formed first coinciding with the stable solution-pH during washing, indicating the completion of ion-exchange process, and a drastic increase in the specific surface-area of the hydrothermal product. The anatase-titania nanotubes are then derived from the pure hydrogen titanate nanotubes via thermal treatment. The use of pure hydrogen titanate and anatase-titania nanotubes for an organic textile dye-removal, from an aqueous solution under the dark condition, via surface-adsorption mechanism has been demonstrated. It is shown that, the specific surface-area and the surface-charge govern the maximum dye-absorption capacity of the anatase-TiO2 nanotubes under the dark condition.
    Journal of Nanoscience and Nanotechnology 02/2011; 11(2):1175-87. DOI:10.1166/jnn.2011.3048 · 1.34 Impact Factor