Abstract
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 Fe0 corrosion to release Fe2+. In, addition, Fe0, 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.
Highlights
The co-contamination of heavy metals and refractory organic compounds in wastewater have become an urgent environmental problem nowadays
The surface morphology and element distribution of pristine sulfidated nanoscale zero-valent iron (S-Nanoscale zero-valent iron (nZVI)) was characterized by scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX) as well as TEM
The above characterization indicates that S-nZVI is a core–shell structure with a coverage of FeS
Summary
The co-contamination of heavy metals and refractory organic compounds in wastewater have become an urgent environmental problem nowadays. One typical example is that chromate (Cr(VI)) is commonly present together with organic pollutants in industrial waste of metal finishing, wood preserving, petroleum refining, and even in contaminated fields. It is well known that Cr(VI) is acutely toxic, carcinogenic and mutagenic to living organisms. Cr(III) is less toxic and can be removed through precipitation [1]. The effective transformation of Cr(VI) into Cr(III) is a preferred method for reducing contamination. The reduction of Cr(VI) and the oxidation of organic pollutants seems theoretically contradictory, making this kind of wastewater difficult to treat [2,3]. Efficient and simultaneous removal of Cr(VI) and organic pollutants is of great significance for water remediation
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