Effective Adsorption of Hexavalent Chromium and Divalent Nickel Ions from Water through Polyaniline, Iron Oxide, and Their Composites

Water pollution caused by industrial wastes containing heavy metals and dyes is a major environmental problem. This study reports on the synthesis, characterization, and utilizations of Polyaniline (PANI) and its composites with Fe3O4 for the removal of hexavalent chromium Cr(VI) and divalent nickel Ni(II) ions from water. The adsorption data were fitted in Freudlich, Langmuir, Tempkin, Dubbanin–Ruddishkawich (D–R), and Elovich adsorption isotherms. The Freundlich isotherm fits more closely to the adsorption data with R2 values of 0.9472, 0.9890, and 0.9684 for adsorption of Cr(VI) on Fe3O4, PANI, and PANI/Fe3O4 composites, respectively, while for adsorption of Ni(II) these values were 0.9366, 0.9232, and 0.9307 respectively. The effects of solution pH, initial concentration, contact time, ionic strength, and adsorbent dosage on adsorption behavior were investigated. The adsorption ability of composites was compared with pristine PANI and Fe3O4 particles. Activation energy and other thermodynamic properties such as changes in enthalpy, entropy, and Gibbs free energy indicated spontaneous and exothermic adsorption

Study on Direct Synthesis of Energy Efficient Multifunctional Polyaniline-Graphene Oxide Nanocomposite and Its Application in Aqueous Symmetric Supercapacitor Devices

The synthesis of promising nanocomposite materials can always be tricky and depends a lot on the method of synthesis itself. Developing such synthesis routes, which are not only simple but also can effectively catch up the synergy of the compositing material, is definitely a worthy contribution towards nanomaterial science. Carbon-based materials, such as graphene oxide, and conjugative polymers, such as conductive polyaniline, are considered materials of the 21st century. This study involves a simple one pot synthesis route for obtaining a nanocomposite of polyaniline and graphene oxide with synergistic effects. The study was carried out in a systematic way by gradually changing the composition of the ingredients in the reaction bath until the formation of nanocomposite took place at some particular reaction parameters. These nanocomposites were then utilized for the fabrication of electrodes for aqueous symmetric supercapacitor devices utilizing gold or copper as current collectors. The device manifested a good capacitance value of 264 F/g at 1 A/g, magnificent rate performance, and capacitance retention of 84.09% at a high current density (10 A/g) when gold sheet electrodes were used as the current collectors. It also showed a capacitance retention of 79.83% and columbic efficiency of 99.83% after 2000 cycles

Physical, Chemical, and Electrochemical Properties of Redox-Responsive Polybenzopyrrole as Electrode Material for Faradaic Energy Storage

Polybenzopyrrole (Pbp) is an emerging candidate for electrochemical energy conversion and storage. There is a need to develop synthesis strategies for this class of polymers that can help improve its overall properties and make it as suitable for energy storage applications as other well-studied polymers in this substance class, such as polyaniline and polypyrrole. In this study, by synthesizing Pbp in surfactant-supported acidic medium, we were able to show that the physicochemical and electrochemical properties of Pbp-based electrodes are strongly influenced by the respective polymerization conditions. Through appropriate optimization of various reaction parameters, a significant enhancement of the thermal stability (up to 549.9 °C) and the electrochemical properties could be achieved. A maximum specific capacitance of 166.0 ± 2.0 F g−1 with an excellent cycle stability of 87% after 5000 cycles at a current density of 1 A g−1 was achieved. In addition, a particularly high-power density of 2.75 kW kg−1 was obtained for this polybenzopyrrole, having a gravimetric energy density of 17 Wh kg−1. The results show that polybenzopyrroles are suitable candidates to compete with other conducting polymers as electrode materials for next-generation Faradaic supercapacitors. In addition, the results of the current study can also be easily applied to other systems and used for adaptations or new syntheses of advanced hybrid/composite Pbp-based electrode materials

Selective transportation of molybdenum from model and ore through poly inclusion membrane

The extraction of molybdenum from the aqueous solution through poly inclusion membrane (PIM) containing tri-caprylylmethylammonium chloride (Aliquat-336) as a carrier has been investigated. A solution of molybdenum in phosphoric acid was used as a feed side while sodium hydroxide was used as stripping reagent. The results indicate that maximum flux value was obtained at 0.16 M Aliquat-336. Increase in H3PO4 concentration from 0.05 to 1.5 M results into an increase in molybdenum ions. The maximum flux of 3.00×10−6 mol/m2s through PIM was found at 1.5 M H3PO4. The optimized conditions were applied for removal of Mo(VI) from ore and more than 97 % Mo(VI) was extracted.   Bull. Chem. Soc. Ethiop. 2020, 34(1), 93-104. DOI: https://dx.doi.org/10.4314/bcse.v34i1.

Achieving Ultrahigh Cycling Stability and Extended Potential Window for Supercapacitors through Asymmetric Combination of Conductive Polymer Nanocomposite and Activated Carbon

Conducting polymers and carbon-based materials such as graphene oxide (GO) and activated carbon (AC) are the most promising capacitive materials, though both offer charge storage through different mechanisms. However, their combination can lead to some unusual results, offering improvement in certain properties in comparison with the individual materials. Cycling stability of supercapacitors devices is often a matter of concern, and extensive research is underway to improve this phenomena of supercapacitive devices. Herein, a high-performance asymmetric supercapacitor device was fabricated using graphene oxide–polyaniline (GO@PANI) nanocomposite as positive electrode and activated carbon (AC) as negative electrode. The device showed 142 F g−1 specific capacitance at 1 A g−1 current density with capacitance retention of 73.94% at higher current density (10 A g−1). Most importantly, the device exhibited very high electrochemical cycling stability. It retained 118.6% specific capacitance of the starting value after 10,000 cycles at 3 Ag−1 and with coulombic efficiency of 98.06 %, indicating great potential for practical applications. Very small solution resistance (Rs, 0.640 Ω) and charge transfer resistance (Rct, 0.200 Ω) were observed hinting efficient charge transfer and fast ion diffusion. Due to asymmetric combination, potential window was extended to 1.2 V in aqueous electrolyte, as a result higher energy density (28.5 Wh kg−1) and power density of 2503 W kg−1 were achieved at the current density 1 Ag−1. It also showed an aerial capacitance of 57 mF cm−2 at current 3.2 mA cm−2. At this current density, its energy density was maximum (0.92 mWh cm−2) with power density (10.47 W cm−2)

Fabrication of Eco-Friendly Solid-State Symmetric Ultracapacitor Device Based on Co-Doped PANI/GO Composite

An eco-friendly solid-state symmetric ultracapacitor (Uc) device was fabricated using a polyaniline graphene oxide composite co-doped with sulfuric acid (H2SO4) and dodecyl benzene sulfonic acid (DBSA) or camphor sulfonic acid (CSA), as electrode material utilizing gold sheets as current collectors. The device showed specific capacitance value of 150 F/g at 1 A/g current density, with a capacitance retention value of 93.33% at higher current density (10 A/g), indicating a high rate capability. An energy density of 15.30 Whkg-1 with a power density of 1716 Wkg-1 was obtained at the current density of 1 A/g. The values of areal capacitance, power density, and energy density, achieved at the current density of 5 mAcm-2, were 97.38 mFcm-2, 9.93 mWhcm-2, and 1.1 Wcm-2, respectively. Additionally, the device showed very low solution and charge transfer resistance (0.885 Ω and 0.475 Ω, respectively). A device was also fabricated utilizing copper as current collector; however, a lower value of specific capacitance (82 F/g) was observed in this case

Enhanced Electrocatalytic Behaviour of Poy(aniline-co-2-hydroxyaniline) Coated Electrodes for Hydrogen Peroxide Electrooxidation

Polymer-coated electrodes are widely used for the detection and oxidation of hydrogen peroxide (H2O2). Conducting polyaniline (PANI), poly (2-hydroxyanilne) (PHA), and their copolymer poly(aniline-co-2-hydroxyaniline) (PACHA) were electrochemically synthesized on a gold substrate for H2O2 detection and analysis. Cyclic voltammetry (CV), square wave voltammetry (SWV), and differential pulse voltammetry (DPV) techniques were used for electroanalysis. Both PACHA and PANI greatly reduced the gold overpotential for H2O2 oxidation with enhanced current densities. The PACHA- and PANI-coated electrodes showed oxidative peaks at 0.30 and 0.50 V, respectively, in the presence of 1.4 × 10−6 M H2O2, while PHA-coated electrodes exhibited no response. The fabricated electrodes displayed a linear response towards H2O2 in range of 2 × 10−7 to 1.4 × 10−6 M, with very low detection limits (LODs) of 1 × 10−7 M (for PACHA) and 1.15 × 10−7 M (for PANI) evaluated from CV data. In case of SWV and DPV, the LODs were found to be 1.78 × 10−7 M (for PACHA) and 1 × 10−7 M (for PANI), respectively. The materials exhibit high sensitivity of 650 A/Mcm2 and show good stability. The PACHA-coated electrode shows better capacitance (1.84 × 10−3 F) than PHA- (2.52 × 10−4 F) and PANI-coated (1.17 × 10−3 F) electrodes

Comparative Study of the Adsorption of Acid Blue 40 on Polyaniline, Magnetic Oxide and Their Composites: Synthesis, Characterization and Application

Conducting polymers (CPs), especially polyaniline (PANI) based hybrid materials have emerged as very interesting materials for the adsorption of heavy metals and dyes from an aqueous environment due to their electrical transport properties, fascinating doping/de-doping chemistry and porous surface texture. Acid Blue 40 (AB40) is one of the common dyes present in the industrial effluents. We have performed a comparative study on the removal of AB40 from water through the application of PANI, magnetic oxide (Fe3O4) and their composites. Prior to this study, PANI and its composites with magnetic oxide were synthesized through our previously reported chemical oxidative synthesis route. The adsorption of AB40 on the synthesized materials was investigated with UV-Vis spectroscopy and resulting data were analyzed by fitting into Tempkin, Freundlich, Dubinin-Radushkevich (D-R) and Langmuir isotherm models. The Freundlich isotherm model fits more closely to the adsorptions data with R2 values of 0.933, 0.971 and 0.941 for Fe3O4, PANI and composites, respectively. The maximum adsorption capacity of Fe3O4, PANI and composites was, respectively, 130.5, 264.9 and 216.9 mg g-1. Comparatively good adsorption capability of PANI in the present case is attributed to electrostatic interactions and a greater number of H-bonding. Effect of pH of solution, temperature, initial concentration of AB40, contact time, ionic strength and dose of adsorbent were also investigated. Adsorption followed pseudo-second-order kinetics. The activation energy of adsorption of AB40 on Fe3O4, PANI and composites were 30.12, 22.09 and 26.13 kJmol-1 respectively. Enthalpy change, entropy change and Gibbs free energy changes are -6.077, -0.026 and -11.93 kJ mol-1 for adsorption of AB40 on Fe3O4. These values are -8.993, -0.032 and -19.87 kJ mol-1 for PANI and -10.62, -0.054 and -19.75 kJ mol-1 for adsorption of AB40 on PANI/Fe3O4 composites. The negative sign of entropy, enthalpy and Gibbs free energy changes indicate spontaneous and exothermic nature of adsorption

Investigation of Alumina-Doped Prunus domestica Gum Grafted Polyaniline Epoxy Resin for Corrosion Protection Coatings for Mild Steel and Stainless Steel

Eco-friendly inhibitors have attracted considerable interest due to the increasing environmental issues caused by the extensive use of hazardous corrosion inhibitors. In this paper, environmentally friendly PDG-g-PANI/Al$_2$O$_3$ composites were prepared by a low-cost inverse emulsion polymerization for corrosion inhibition of mild steel (MS) and stainless steel (SS). The PDG-g-PANI/Al$_2$O$_3$ composites were characterized by different techniques such as X-ray diffraction (XRD), UV/Vis, and FTIR spectroscopy. XRD measurements show that the PDG-g-PANI/Al$_2$O$_3$ composite is mostly amorphous and scanning electron micrographs (SEM) reveal a uniform distribution of Al$_2$O$_3$ on the surface of the PDG-g-PANI matrix. The composite was applied as a corrosion inhibitor on mild steel (MS) and stainless steel (SS), and its efficiency was investigated by potentiodynamic polarization measurement in a 3.5% NaCl and 1 M H$_2$SO$_4$ solution. Corrosion kinetic parameters obtained from Tafel evaluation show that the PDG-g-PANI/Al$_2$O$_3$ composites protect the surface of MS and SS with inhibition efficiencies of 92.3% and 51.9% in 3.5% NaCl solution, which is notably higher than those obtained with untreated epoxy resin (89.3% and 99.5%). In particular, the mixture of epoxy/PDG-g-PANI/Al$_2$O$_3$ shows the best performance with an inhibition efficiency up to 99.9% on MS and SS. An equivalent good inhibition efficiency was obtained for the composite for 1M H$_2$SO$_4$. Analysis of activation energy, formation enthalpy, and entropy values suggest that the epoxy/PDG-g-PANI/Al$_2$O$_3$ coating is thermodynamically favorable for corrosion protection of MS and exhibits long-lasting stability