Reuse of PANI wastewater treated by anodic oxidation/electro-Fenton for the preparation of PANI

Abstract

The present work investigated the treatment of the polyaniline (PANI) wastewater by anodic oxidation/electro-Fenton and reusing the treated PANI wastewater for the preparation of PANI. Organics were degraded by hydroxyl radical (OH) and sulfate radical (SO₄^-) formed simultaneously in the wastewater from electro-Fenton reaction and the anode surface. Under the conditions of 160 mL min^-1 oxygen flow rate, constant current density 14 mA cm^-2 and Fe²⁺ concentration 0.2 mM, 89% COD can be removed from the PANI wastewater after 360 min treatment. The energy consumption was 50 kWh (kg COD)^-1 and the current efficiency was 27.8%. After the PANI wastewater treatment, the aniline, aniline derivatives and aniline oligomers were removed from the wastewater. The PANI obtained using fresh solution, treated PANI wastewater and untreated PANI wastewater were recorded PANI-F, PANI-T and PANI-U, respectively. In the preparation of PANI-U, the reaction of p-benzoquinone with aniline or aniline oligomers could change the nucleation and growth, leading to the production of aggregated nanoparticles and low specific capacitance. However, the morphology and specific capacitance of PANI-T were similar to that of PANI-F. The PANI-T is three-dimensional sphere of nanofibers with high specific capacitance about 446.7 F g^-1. The yield of PANI-T using treated PANI wastewater could reach to 92.1%. These results demonstrate that the PANI wastewater treatment approach is efficient and environmentally friendly.

Keywords: COD removal; Coupled process; Oligomers; Reusing the wastewater; Specific capacitance; p-benzoquinone.