Preparation Of Electroactive α-ZrP/PANI Hybrid Film And Its Esix Performance For Pb²⁺

Electroactive material (EM), electronic-ionic mixed conductor, can becharged/discharged through the external electric circuit or by solute redox agent.Meanwhile, the transferred electronic charge has to be compensated by ionexchange between this medium and electrolyte solution. This material is widelyemployed in electrochemically switched ion exchange, electrochemical energyconversion and storage, electronic devices and sensors, super capacitor,electrochromics, ion-selective electrodes, etc. Such EM mainly involve ininorganic solids with mixed-valence transition metals (hexacyanoferrate),conducting polymers (PANI, PPy, PEDOT) and organic-inorganic hybridmaterials, etc. The hybrid metrial which incorporates the advantages of organicand inorganic materials has been the research interests.In this work, an electroactive hybrid film composed of amorphousα-zirconium phosphate and polyaniline (α-ZrP/PANI) is controllably synthesizedon carbon nanotubes (CNTs) modified Au electrodes in aqueous solution byelectrochemistry method. This hybrid film is applied to the treatment of heavymetal wastewater by electrically switched ion exchange (ESIX), which can notonly improve the ion exchange velocity and capacity but also reduce secondarypollution via a potential triggered reversible switching process. The highlycrystalline α-ZrP is synthesized by hydrothermal method at first and thenexfoliated to amorphous α-ZrP nanosheets. The hybrid film shows excellentpotential-triggered adsorption of Pb2+ion due to the selective complexation ofPb2+ion with oxygen derived from the exposed group P-OH of α-ZrP. Herein,α-ZrP, as a weak solid acid, can provide an acidic micro-environment for the redox process of PANI to promote the electroactivity in neutral aqueoussolutions. Electrochemical quartz crystal microbalance (EQCM), scanningelectron microscopy (SEM) and X-ray power diffraction (XRD) analysis areapplied for the evaluation of the synthesis process. It is found that the exfoliatedα-ZrP nanosheets are well dispersed in PANI to form the amorphousα-ZrP/PANI hybrid film. The insertion/release of heavy metals into/from thefilm is reversibly controlled by a potential-triggered mechanism. X-rayphotoelectron spectroscopy (XPS) and atomic absorption spectrophotometer(AAS) are employed to study the adsorption selectivity of this hybrid filmtowards heavy metals.In the present study, we develop a method for preareing α-ZrP/PANI hybridfilm with three-dimensional porous structure on a PANI oligomers-modifiedmatrix by the two-step electrodeposition method. The first layer of PANIoligomers is synthesized by pulse potentiostatic method (PPM). The aminos inthe end of PANI serve as active site to trigger the continue growth of PANI, andthe α-ZrP is deposited at the same time. The ion exchange capacity and cyclestability of this hybrid film is improved by controlling the composition ofpreparation solution and synthesis parameters. EQCM technique is employed toin-situ detect the growth and ion exchange of the hybrid film on the top of thequartz crystals. Fourier transform infrared spectrometer (FT-IR), X-ray powerdiffraction (XRD), scanning electron microscopy (SEM) and X-rayphotoelectron spectroscopy (XPS) are applied for the analysis of morphology,crystal structure and collaborative mechanisms of α-ZrP/PANI hybrid film. Theresults shows that the fibrous hybrid film exhibits high ion exchange capacity(up to122.93mg/g), which is nine times higher than that hybrid film depositedon CNTs. This kind of novel hybrid film is expected to be a promisingpotential-triggered ESIX material for separation and recovery of heavy metalions from wastewater.