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Conducting polypyrrole-nickel oxide (polypyrrole-NiO) composites were synthesized by in situ deposition technique by placing different weight percentages of NiO powder (10, 20, 30, 40, and 50%) during the polymerisation of pyrrole. The polypyrrole-NiO composites were later characterised with Fourier transform infrared spectroscopy (FTIR) which confirms the presence of polypyrrole in the composite. AC conductivity was studied in the frequency range from 102 to 107 Hz. From these studies it is found that AC conductivity remains constant at low frequency and increases rapidly at higher frequency, which is the characteristic behavior of disordered materials. The dielectric behavior of these composites was also investigated in the frequency range 102–107 Hz. It is observed from these studies that the dielectric constant and dielectric tangent loss decrease exponentially with frequency. The composites exhibit a low value of dielectric loss at higher frequency.

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The objectives of present work emphasize the successful usage of Fe(III) modified layered double hydroxide clays with reduced graphene support (Si-rGO/LDH-Fe) for the removal of V(V) and Se(IV) from aqueous systems. The precursors along with the modified and sorbent loaded materials were successfully characterized by BET surface area analyzer, SEM-EDS mapping, FTIR, potentiometric titrations and XPS analysis. Sorption performance of Si-rGO/LDH-Fe towards V(V) and Se(IV) under optimized conditions such as pH, temperature and concentration were investigated. The equilibrium and kinetic investigations revealed that the adsorption of V(V) and Se(IV) onto Si-rGO/LDH-Fe follows non-linear Langmuir isotherm and pseudo-second-order model, respectively. The equilibrium reached within 120 min and the Langmuir isotherm fit well with the experimental data. The adsorption mechanism was proposed to be ligand exchange with electrostatic interactions. Such results indicated that V(V) and Se(IV) species interact by the protonated hydroxyl moieties on the surface of Si-rGO/LDH-Fe. The practical efficacy and effectiveness of Si-rGO/LDH-Fe was also compared with some of the related works reported so far. The regeneration capacity and reusability of Si-rGO/LDH-Fe were also tested by employing four cycles of desorption experiments.

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