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An ultrasound-assisted situ oxidation process has been demonstrated for the Cr(VI) adsorption experiment with PPy, PPy/Fe3O4 and PPy/Fe3O4/AgCl composite in a relatively wide pH range. The PPy, PPy/Fe3O4 and PPy/Fe3O4/AgCl composite were characterized with XRD, SEM, TEM and VSM measurements, and were further tested in the role of Cr(VI) adsorption in aqueous solution. Up to 100 % adsorption was found with 500 or 1000 mg L−1 Cr(VI) aqueous solution at pH 3.0. Adsorption results showed that Cr(VI) removal efficiency by PPy, PPy/Fe3O4 and PPy/Fe3O4/AgCl decreased with an increase in pH. Compared with contact time (30 min) of PPy and PPy/Fe3O4 adsorbent, 15 min adsorption of PPy/Fe3O4/AgCl composite can almost reached the adsorption equilibrium. The kinetics of Cr(VI) adsorption with PPy, PPy/Fe3O4 and PPy/Fe3O4/AgCl follow the pseudo-second-order model. The eco-friendly PPy/Fe3O4/AgCl featured with magnetism and excellent reusability offers a promising adsorbent material for Cr(VI) contaminated water.

PPy/Fe3O4/AgCl composites were prepared via in situ polymerization for the removal of highly toxic Cr(VI). The structure and morphology of the prepared composites were characterized by the XRD, SEM, TEM, and VSM examinations. Up to 100 % removal was found with 1000 mg/L Cr(VI) aqueous solution at pH 2.0. The process of Cr(VI) ions’ adsorption was easy to reach equilibrium at higher temperatures. Adsorption results showed that Cr(VI) removal efficiency by the composites decreased with an increase in pH. Adsorption kinetics was described by the pseudo-second-order rate model. Isotherm data fitted well to the Langmuir isotherm model. Desorption experiment showed that the regenerated adsorption of PPy/Fe3O4/AgCl can be reused successfully for three times successive adsorption–desorption cycles without appreciable loss of its original capacity.

Polypyrrole/NiFe2O4 (PPy/NiFe2O4) composites were prepared by ultrasonic oxidative polymerization in the presence of NiFe2O4 nanoparticles (NPs). The nanostructure of PPy/NiFe2O4 was confirmed by the X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM) examinations. The adsorption of Cr(VI) onto the PPy/NiFe2O4 composite was lowly pH dependent and the adsorption kinetics followed the Pseudo-second-order model. The Langmuir isothermal model well described the adsorption isotherm data and the maximum adsorption capacity increased with the increase of temperature. The maximum adsorption capacity of the PPy/NiFe2O4 for Cr(VI) ions was up to 50 mg/g at pH 2.0. The excellent adsorption characteristic of PPy/NiFe2O4 composite will render it a highly efficient and economically viable adsorbent for Cr(VI) ions removal. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Highly conductive polypyrrole/graphene/manganese dioxide (PPy/graphene/MnO2) composites are fabricated via ultrasonic irradiation using p-toluenesulfonic acid as a dopant. The microstructures of PPy/graphene/MnO2 are evidenced by the SEM and TEM examinations. The effects of the graphene and MnO2 loading on the electrical conductivity are investigated. The maximum conductivity of PPy/graphene/MnO2 composites about 17.15 S/cm found with 3 wt% graphene and 48.7 wt% MnO2 at room temperature. Such uniform structure together with the observed high conductivities afforded high specific capacitance. A specific capacitance of as high as 258 F/g at a current density of 1 A/g was achieved over the PPy/graphene/MnO2 composite.

NiO nanospheres have been synthesized by using magnetic stirring and ultrasound methods. The structure and morphology of synthesized samples were characterized by X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. The results show the NiO nanospheres prepared by the ultrasonic method are far less than that prepared by the stirring method. Moreover, in the presence of surfactant, the average diameter of NiO nanospheres prepared by the ultrasonic method is only 1–3 nm. The capacitance of NiO electrodes was investigated with cyclic voltammetry. The NiO prepared by the ultrasonic method exhibited higher specific capacitance of ~260 F g −1 at 1 A g −1 current density.

Highly conductive PPy/graphite nanosheets/rare earth ions (PPy/nanoG/RE3+) composites were prepared via in-situ polymerization with p-toluenesulfonic acid as a dopant and FeCl3 as an oxidant. The microstructures of nanoG and PPy/nanoG/RE3+ were characterized by the SEM and TEM examinations. It was found that nanoG and PPy nanospheres formed the uniform composite with the PPy nanospheres embedded on the nanoG surface and/or filled between the nanoG. The effects of nanoG and RE3+ on the electrical conductivity and electrochemical performance of the composites were investigated. The results showed that the nanoG and RE3+ as the filler had effect on the conductivity and electrochemical performance of PPy/nanoG/RE3+ composites, which played an important role in forming a conducting network in PPy matrix. A specific capacitance of as high as 175 F/g at a current density of 1 A/g was achieved over the PPy/nanoG/Gd3+ composite. The capacitance of the PPy/nanoG/Gd3+ composite decreased only 5.1% after 800 charging/discharging cycles at a current density of 1 A/g. POLYM. ENG. SCI., 54:2731–2738, 2014. © 2013 Society of Plastics Engineers

Highly conductive polypyrrole/graphene nanosheets/NiO (PPy/GNS/NiO) composites are fabricated via ultrasound technique using p-toluenesulfonic acid as a dopant and FeCl3 as an oxidant. The effects of the GNS and NiO loading on the electrical conductivity are investigated. The maximum conductivity of PPy/GNS/NiO composites about 24.39 S/cm found with 3 wt% GNS and 48.7 wt% NiO at room temperature. The results showed that the high-aspect-ratio structure of GNS played an important role in forming a conducting network in PPy matrix. The microstructures of PPy/GNS/NiO are evidenced by the scanning electron microscope and transmission electron microscope examinations. The cyclic voltammetry curves can be seen that the PPy/GNS/NiO composites also have good electrochemical performance, and it can be used as a supercapacitor electrode material. POLYM. COMPOS., 34:997–1002, 2013. © 2013 Society of Plastics Engineers

Highly conductive PPy/graphene nanosheet and PPy/graphene nanosheet/Gd3+ composites were prepared via in-situ polymerization with p-toluenesulfonic acid as a dopant and FeCl3 as an oxidant. The effects of graphene nanosheet obtained by two different synthetic methods and Gd3+ on the electrical conductivity of the composites were investigated. The results showed that the graphene nanosheet as a filler had an effect on the conductivity of PPy/graphene nanosheet similar to PPy/graphene nanosheet/Gd3+ composites, which played an important role in forming a conducting network in PPy matrix. Thermal gravimetric analysis demonstrated an improved thermal stability of PPy in the PPy/graphene nanosheet/Gd3+ composites. The microstructures of PPy/graphene nanosheet/Gd3+ were characterized by scanning electron microscope and transmission electron microscope examinations.

Highly conductive polypyrrole/graphite nanosheets/Gd3+ (PPy/nanoG/Gd3+) composites are fabricated via in situ polymerization using p-toluenesulfonic acid as a dopant and FeCl3 as an oxidant. The effects of the graphite nanosheets and Gd3+ loading on the electrical conductivity are investigated. The maximum conductivity of PPy/nanoG/Gd3+ composites about 17.86 S/cm found with 3 wt% graphite nanosheets and 6 wt% Gd3+ at room temperature. The results showed that the high-aspect-ratio structure of graphite nanosheets played an important role in forming a conducting network in PPy matrix. Thermal gravimetric analysis demonstrates an improved thermal stability of PPy in the PPy/nanoG/Gd3+ composites. The microstructures of PPy/nanoG/Gd3+ are evidenced by the SEM and TEM examinations. POLYM. COMPOS., © 2011 Society of Plastics Engineers.