Degradation of the endocrine-disrupting 4-nonylphenol by ferrate(VI): biodegradability and toxicity evaluation

4-Nonylphenol (4-NP) is an endocrine-disrupting and persistent chemical and is partially degraded in conventional wastewater treatment processes. Ferrate(VI) can be used as an environment-friendly oxidizing agent to mediate 4-NP degradation. Thus, this paper evaluates the biodegradability of 4-NP and its degradation products after the addition of ferrate(VI). The biodegradability was examined using NP labeled with C-14 as a tracer and activated sludge microorganisms as an inoculum. The addition of ferrate(VI) to the 4-NP solution spiked with the tracer resulted in no remarkable decrease in the concentration of C-14, indicating incomplete mineralization of 4-NP and formation of degradation products. The degradation products from 4-NP with Fe(VI) were estimated based on mass spectra, which detected a unique peak at m/z 223 at low intensity. Four hydrogen atoms might have been added to 4-NP by degradation with Fe(VI). In addition, the effect of ferrate(VI) concentration on the estrogenic activity of 4-NP in an aqueous solution was investigated using a yeast bioassay. The results show that estrogenic activity was significantly decreased at a mass ratio of Fe(VI) to 4-NP greater than or equal to 2.5.

Automated summary

In this study, the biodegradability of 4-NP and its degradation products in the presence of ferrate(VI) were evaluated. It was found that 4-NP was not completely mineralized and formed degradation products when ferrate(VI) was added. Mass spectra analysis revealed a unique peak at m/z 223 for the degradation products of 4-NP with Fe(VI). Furthermore, the estrogenic activity of 4-NP in aqueous solution was significantly reduced with increasing Fe(VI) concentration.