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Mn 2+ ion was doped into the sol-gel anatase TiO 2 in the concentration range of 0.02-0.1%. Powder X-ray diffraction results revealed that the phase transformation from anatase to rutile proceeds at a slower rate up to an intermediate dopant concentration of 0.06% and accelerates for a higher dopant concentration of 0.1%. In comparison with the previous studies, the phase transition temperature was reduced by 100 °C for the intermediate dopant concentration. The photocatalytic activity of Mn 2+ (0.06%)-TiO 2 for the degradation of an oxo-fused polycyclic aromatic dye, Indanthrane BR Violet, was almost equal to that of Degussa P-25 under UV light, but under solar light its efficiency was nearly 4 times higher. This enhanced activity can be attributed to the (i) synergistic effect in the bicrystalline framework of anatase and rutile, (ii) small crystallite size, and (iii) high intimate contact between both the phases. The correlation of the crystallite size with the synergistic effect on the photocatalytic activity is studied in detail.

inclusion. The rutile fraction increased with Mn 2+ concentration due to the creation of surface oxygen vacancies. All the doped catalysts showed red shift in the band gap absorption to the visible region. The photocatalytic activities of these catalysts were evaluated in the degradation of Aniline Blue (AB) under UV/solar light. Among the photocatalysts, Mn 2+ (0.06 at.%)-TiO 2 showed enhanced activity, which is attributed to the synergistic effect in the bicrystalline framework of anatase and rutile. Further the unique half filled electronic structure of Mn 2+ serves as a shallow trap for the charge carriers to enhance the photocatalytic activity. An insight to the mechanism of interfacial charge transfer in the mixed phase of anatase and rutile is explored, taking into consideration the theories of previous models.

In the present investigation nano copper ferrite, CuFe 2 O 4 (CF) is synthesized by one pot energy saving solution combustion synthesis. The combustion derived copper ferrite nanoadsorbent is characterized by powder X-ray diffraction, Fourier transform infra-red spectroscopy, scanning electron microscopy, transmission electron microscopy and UV-Vis spectroscopy. The magnetic behavior is studied by Vibrating sample magnetometer measurements and the results shows it's a soft ferromagnet with low saturation magnetization and coercive effect. CF nanopowder is used as good magnetically separable nanoadsorbent. Adsorption property is evaluated by the removal of malachite green, a dye which is widely used by many industries, from its aqueous solution. Various parameters like contact time (5-30 min), adsorbent loading (0-45 mg) are investigated systematically by batch experiments. Adsorption isotherms and kinetic studies also conducted which shows that the adsorption follows pseudo second order mechanism. The experimental data fitted well with the Langmuir isotherm (R 2 = 0.978), yielding a maximum adsorption capacity of 22 mg/g. The optimum adsorbent dose was found to be 40 mg/L and stirring time experiment reveals that 85% of decolourization was observed for 30 min of stirring at neutral pH which is much more efficient than those reported in literature. Graphical abstract

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