Polypyrrole/reduced graphene oxide aerogel particle electrodes for high-efficiency electro-catalytic synergistic removal of Cr(VI) and bisphenol A

In this paper, synthesis of polypyrrole/reduced graphene oxide aerogel (PGAs) as particle electrodes and their application in three-dimensional electrode system for simultaneous reduction of hexavalent chromium (Cr(VI)) and oxidation of bisphenol A (BPA) were implemented firstly. Electro-catalytic properties were investigated systemically in terms of the influences of pivotal factors, such as pH, the concentration ratio of Cr(VI) and BPA, voltage and the ratio of PGAs mass to solution volume (S/L). The results showed superb removal rates of 98.52 +/- 1.48% for Cr(VI) and 98.00 +/- 1.17% for BPA within 30 min under the optimal conditions. Furthermore, synergy of both pollutants was testified by the comparison of removal rates in electro-catalytic kinetics and their fitting in mixed solution with k(obs-Cr(VI)) = 0.2019 min(-1), k(obs-BPA) = 0.1463 min(-1) significantly higher than that in one-component aqueous solution (k(obs-Cr(VI)) = 0.0397 min(-1), k(obs-BPA) = 0.0417 min(-1)). After 20 cycles of experiments, there were still high contaminants and total organic carbon (TOC) removal rates, which showed excellent reutilized ability of PGAs. More deeply, final destination of Cr(VI) was analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX). Meanwhile, intermediates of BPA oxidized with the aid of Cr(VI) and center dot OH were analyzed and a possible degradation pathway was proposed. Importantly, Cr(VI)/BPA system provided a remarkable example of a waste control by waste strategy for the synergetic removal.