Synthesis and characterization of carbon microtube/tantalum oxide composites and their photocatalytic activity under visible irradiationElectronic supplementary information (ESI) available: The particles size graphs, cotton fiber powder XRD, cotton FESEM/EDX, FESEM/TEM-EDAX spectras of composites, pore volume graphs, absorption plots of XO and MO, the Raman, DRS (smoothed) and XRD patterns of the recovered catalysts are given in the electronic supplementary information. See DOI: 10.1039/c5ra0681

Carbon microtubes (CMTs) were synthesized by the combustion of cotton fibers in an open air atmosphere at an optimized temperature. The combustion of the cotton fibers leads to the formation of CMTs by a self rolling approach. In situ synthesis of the CMT : Ta 2 O 5 composite was done in an alkaline ethanolic medium. The formation of the CMTs and composites was characterized by RAMAN, DRS/UV-Visible, FTIR, XPS, XRD, BET, N 2 -adsorption isotherms, FESEM/EDX, TEM/EDX and particle size analysis. The composites were effectively employed in the photo oxidation of xylenol orange (XO) and methyl orange (MO). The composites catalytic activity and the adsorbed dyes removal percentage were determined by a spectrophotometric method. The CMT : Ta 2 O 5 composites attained a higher photocatalytic activity due to the formation of nascent oxygen during degradation, which enhances the photocatalytic performance. The kinetic parameters obey the pseudo -first order reaction, which may be due to the constant amount of the catalyst and the concentration of the dye solution. The catalytic activity of the recycled composites was compared with the catalytic activity of the fresh catalyst. The CMT/Ta 2 O 5 composites were used as photocatalyst in the degradation of xylenol orange and methyl orange dyes.