Hydrogen Peroxide Activation with Sulfidated Zero-Valent Iron for Synchronous Removal of Cr(VI) and BPA

In this work, the synchronous removal of Cr(VI) and bisphenol A (BPA) in a heterogeneous Fenton process with sulfidated nanoscale zero-valent iron (S-nZVI) as the reductant and catalyst was systematically evaluated. Compared to other systems including S-nZVI or H2O2 alone, a simultaneous BPA degradation and Cr(VI) removal could be achieved in the S-nZVI/H2O2 system at an optimum pH of 3. It was, interestingly, found that 7.8% of BPA and 98.2% of Cr(VI) were removed within 60 min in presence of S-nZVI alone, whereas, correspondingly, 98.2% of BPA and 96.9% of Cr(VI) were eliminated in the S-nZVI/H2O2 system. Specifically, humic acid (HA) and H2PO4- inhibited the deterioration of BPA but posed no significant effect on Cr(VI) removal. NO3- had a slight lifting effect on the removal of BPA and Cr(VI), while HCO3- showed a relatively weak prohibition. Experiments with EPR and radical probe tests also provide direct evidence that hydroxyl radicals was monitored in the S-nZVI/H2O2 system, which not only degraded BPA but also inhibited the reduction of Cr(VI). It could not be ignored that FeS accelerated Fe-0 corrosion to release Fe2+. In, addition, Fe-0, Fe2+ and S2+ could react with Cr(VI) while the most of produced Cr(III) was co-precipitated in the form of CrxFe1-xOOH film. The study confirmed that it was feasible for S-nZVI/H2O2 system to remove synchronously organic pollutants and heavy metal.