Performance characteristics of peel of Artocarpus nobilis fruit can be enhanced by the treatment of the biosorbent with aqueous NaOH solutions under stirred conditions, followed by thorough washing of the treated biosorbent with water. A series of experiments performed within a wide range of solution pH demonstrates that the optimum pH for Cr(III) removal is pH 5.0, while it is 2.0 for Cr(VI) by peel of Artocarpus nobilis fruit after treatment with aqueous NaOH solutions of concentrations varied from 0.0050 to 0.15 M. Adsorption of Cr(III) and Cr(VI) from individual aqueous solutions on the above biosorbent treated with 0.010 M NaOH solution, which provides the highest extent of removal of 4.89 × 10 3 mg kg −1 (pH = 5) and 4.94 × 10 3 mg kg −1 (pH = 2), respectively, follows pseudo-first-order kinetics at the ambient temperature of 27.5 °C when the concentration of adsorbate concentration is kept relatively constant. The order of the reaction is unchanged when the solution temperature is increased up to 40.0 °C for Cr(III) although the reaction becomes pseudo-second order for Cr(VI). Further, the energy of activation for adsorption of Cr(III) is determined to be 66.82 kJ mol −1 , suggesting a strong attraction between the adsorbate and the biosorbent. Application of the intraparticle diffusion model to kinetics data within the early stages of the adsorption process of Cr(III) suggests that boundary layer-retarded diffusion be valid at both solution temperatures, while no retardation be possible for Cr(VI) at the warmer temperature.Keywords Chromium species · NaOH treatment · Biosorbent · pH effect Abbreviations NWBF1 0.005 M NaOH-treated peel of Artocarpus nobilis fruit NWBF2 0.010 M NaOH-treated peel of Artocarpus nobilis fruit NWBF3 0.020 M NaOH-treated peel of Artocarpus nobilis fruit NWBF4 0.050 M NaOH-treated peel of Artocarpus nobilis fruit NWBF5 0.100 M NaOH-treated peel of Artocarpus nobilis fruit NWBF6 0.150 M NaOH-treated peel of Artocarpus nobilis fruit MB Methylene blue * N. Priyantha

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Dye sensitized solar cells have attracted lot of research interest in recent years due to their low production cost, higher transparency, easy fabrication and tunable optical properties. Generally, Platinum is used as the catalytic active counter electrode material in the cell which has achieved about 14.1% efficiency. Platinum is an expensive and rare metal and is susceptible to corrosion in long term applications. Therefore lot of research interest is focused on finding low cost, earth abundant alternatives as the counter electrode materials. Due to the low cost, higher conductivity, higher stability, easy preparation and easy fabrication, conducting polymers have become an advanced alternative. Generally, product performance of polymers has improved by blending two or more polymers. Conductivity, stability, structures and performances of pure polyaniline and pure polypyrrole are highly investigated. Among all counter electrode fabricated with conducting polymers, polyaniline has shown the highest power conversion efficiency in dye sensitized solar cells. Performance changes of dye sensitized solar cells have been discussed here by fabricating the counter electrode with polymer blends with different mass ratios of polyaniline and polypyyrole. Out of all the blends tested, polymer blend with 1:1 mass ratio of polyaniline:polypyrrole showed the lowest charge transfer resistance and highest efficiency in Dye-Sensitized Solar Cells.