Wastewater from sewage treatment plants containing 17α-estradiol (αE 2 ) has a high potential to cause environmental and human toxicity. Integration of adsorption and Fenton-like oxidation is one of the potential approaches to enhance αE 2 removal. In this study, one-step biosynthesized iron nanoparticles/reduced graphene oxide (FeNPs/rGO) by tea extract was successfully used for αE 2 removal. The results showed that the removal of αE 2 by FeNPs/rGO increased to 56.1%, being only 25.4% and 45.4% for rGO and FeNPs, respectively, indicating that both adsorption and Fenton-like oxidation enhanced the removal of αE 2 , where was confirmed by HPLC-UV. To understand the removal mechanism, characterizations, including ESR, SEM, EDS, FTIR and XPS were used to elucidate the specific roles of rGO and FeNPs in the adsorption and oxidation of αE 2 , and results showed that αE 2 was adsorbed as a monolayer on the surface of rGO via π–π bond interactions and that FeNPs underwent reactions with H 2 O 2 to generate ·OH for αE 2 degradation. Thereafter, a αE 2 degradation pathway was proposed via identification of degradation products (e.g., C 18 H 22 O 3 ) by HPLC-MS. Moreover, the removal of αE 2 by FeNPs/rGO conformed to the Langmuir isotherm with pseudo-first-order adsorption kinetics and pseudo-second-order degradation kinetics. Based on these evidences, the removal of αE 2 by FeNPs/rGO was presented.
Recently, estrogen has attracted widespread concern because it is increasing being detected in wastewater treatment plants. While techniques for estrogen removal have been reported, these have mostly focused on exploring the effect on removal using simple single-factor experiments, rather than applying more complex multifactor mathematical models to wastewater treatment. In this study, reduced graphene oxide-based iron nanoparticles (rGO@Fe NPs) were used for 17α-estradiol (αE 2 ) removal based on adsorption and Fenton oxidation . A response surface methodology , based on a Box-Behnken design, was used to determine the relationships between critical operation factors (pH, temperature, αE 2 concentration, rGO@Fe NPs dose and H 2 O 2 concentration) and removal efficiency to establish the optimal conditions for 1 mg L −1 αE 2 removal. Under the determined optimal reaction condition of pH 6.0, temperature 40 °C, 0.08 g L −1 rGO@Fe NPs dose and 6 mM H 2 O 2 , a maximum removal efficiency of 99.9% was obtained. Subsequently, the presence of co-existing anions (Cl − , SO 4 2− and NO 3 − ) significantly decreased the removal efficiency of αE 2 . However, αE 2 removal from domestic wastewater could be increased by 38.0% when applying RSM results. Moreover, αE 2 removal by rGO@Fe NPs remained stable over five reuse cycles indicating that rGO@Fe NPs would be an efficient and practical advanced materials for αE 2 removal.
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