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The kinetics and thermodynamics of the biosorption of textile dye Congo Red on anaerobic activated sulfidogenic sludge were examined. The influence of different adsorption parameters such as pH, temperature, contact time and initial dye concentrations on the biosorption capacity was also investigated. The sulfidogenic sludge showed a maximum biosorption density of 238.90 mg dye/g cell for Congo Red at an initial dye concentration of 1,000 mg/L, pH 3.5 and 22°C, which is higher than that of many other adsorbents reported in the literature. The biosorption processes obeyed the Langmuir isotherm and exhibited pseudo-second-order rate kinetics. The thermodynamic parameters indicated the spontaneous and exothermic nature of Congo Red biosorption. The Fourier transform infrared spectra revealed the dye interaction with the biomass. Scanning electron microscopy showed significant changes in the surface morphology of the sludge after dye biosorption. These results showed that sulfidogenic sludge biomass is an attractive alternative low-cost biosorbent for the removal of the dye from aqueous media.

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The polyaniline (PANI) is an eco-friendly conductive polymer which has been considered for diverse applications. The partially oxidized phase of the PANI is useful for the charge storage application. Here, a unique nanograin/nanofiber structured PANI was grown on inexpensive stainless steel (SS) current collector by the simple oxidative polymerization process and its charge storage properties were systematically investigated. For that, the inexpensive successive ionic layer adsorption reaction method was used to grow a uniform nanostructured PANI on the SS conductor. This evolution of the nanostructure was studied with the Field emission scanning electron microscope. Furthermore, the as-prepared PANI was confirmed by the X-ray diffraction and the Fourier-transform infrared spectroscopy. In the half cell electrochemical testing, the prepared PANI exhibited a maximum specific capacitance of 710 F g −1 with a specific discharge capacity of 119 mAh −1 at 0.2 mA cm −2 in 1 M H 2 SO 4 for the supercapacitor application. Also, by using the power-law relation it was observed that, in a charging and a discharging current, initially a contribution of the diffusive faradaic reactions is more as compared with the surface capacitive non-faradaic reactions.