Polyaniline was synthesized by the oxidative polymerization method by using ammonium persulfate as an oxidant. The positive charge in the backbone of the polymer was generated by using Potash alum as a dopant. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray fluorescence (XRF), and X-ray diffraction (XRD) techniques were used for characterization of doped polyaniline. The doped polyaniline can be used for selective adsorption of various dyes (selectively sulfonated dyes) from aqueous solution. Adsorption studies regarding the effect of contact time, initial dye concentration, pH, doses of adsorbent, and temperature on adsorption kinetics were investigated. The influence of other anions like Cl(-), NO3(-), and SO4(2-) on the adsorption density of dyes onto doped polyaniline was also explored. Langmuir isotherm and pseudo-second-order kinetics were found to be the most appropriate models to describe the removal of anionic dyes from water through adsorption. Thermodynamic parameters such as free energy (ΔG(0)), enthalpy (ΔH(0)), and entropy (ΔS(0)) changes were also evaluated. The interaction of dyes with doped polyaniline was also investigated by FTIR and UV spectroscopy.

Polyaniline and sodium alginate nanocomposite was synthesized and it was used for selective removal of both cationic and anionic dyes from water at different pH.

This work demonstrates an easy and green method to synthesize alum doped nanopolyaniline (NDPANI). Nanopolyaniline was synthesized by using a template free interfacial polymerization of aniline using APS as oxidant. An environment friendly and nontoxic substance, potash alum, in contrast to hazardous mineral acid, was used as a dopant to create positive charge in the polymer backbone. This material promises a greener method for selective removal of anionic dyes like Orange-II (O-II) and Mordant Yellow (MY) from wastewater. The synthesized alum doped nanopolyaniline (NDPANI) was characterized by FTIR, Xray fluorescence (XRF), SEM, and DLS. The adsorption was studied by variation of adsorbent dosage, pH, temperature, time, and initial concentration of anionic dyes under different reaction conditions. Adsorption of dye follows pseudo-second-order kinetics. Langmuir isotherm was found to be the best fitting model with the maximum adsorption capacity for O-II being 667 mg/g at 308 K. The thermodynamic parameters such as the Gibbs free energy change (ΔG°), enthalpy change (ΔH°), and entropy changes (ΔS°) were calculated and revealed that the adsorption process is spontaneous and endothermic in nature. The material exhibits enhanced dye adsorption capacity and can be used for removal of O-II effectively.

Polyaniline (PANI), synthesized by oxidative polymerization method, is doped with different concentration of Potash alum. The structure and properties of Potash alum doped polyanilines are inves tigated by FTIR, UV-Vis spectroscopy, scanning electron microscopy (SEM), X ray diffraction (XRD), X ray Fluorescence Spectrophotometer (XRF) and conductivity measurement. The ac conductivity of the samples is measured at room temperature. The ac conductivity of the PANI increases from 1.32 × 10 -3 to 12.37 × 10 ⎯3 Ω -1 cm -1 with increase in potash alum concentration at high frequency region. The advantage of this method is that dopant used here is cheap and non toxic in nature when compared with toxic mineral acid, which is widely used as dopant for polyaniline.