Magnetic Fe3O4@NiO hierarchical structures: preparation and their excellent As(v) and Cr(vi) removal capabilities
Authors: Shouwei Zhang
Jiaxing Li
Tao Wen
Jinzhang Xu
Xiangke Wang
Journal: RSC Advances (2013)
Discipline: CHEMISTRY
Keywords: Fe3O4@NiO; hierarchical architectures; solvothermal route; microspheres; specific surface area

Abstract: Uniform three-dimensional (3D) flowerlike Fe3O4@NiO hierarchical architectures were synthesized by a simple and direct solvothermal route without any linker shell. The shell thickness and hierarchical structure of the microspheres can be tuned by adjusting the reaction duration. The size of the hierarchical microspheres is 250–300 nm and the shell is composed of several nanoflakes with a thickness of 20–30 nm and a width of 50–60 nm. The microspheres possess high specific surface area of 125.63 m2 g\u22121 and high saturation magnetization, which allows them to have strong removal ability and are easily separated from solution by magnetic separation method. The microspheres are applied as adsorbents for As(V) and Cr(VI) ions removal from wastewater, and exhibit a high adsorption capacity with an adsorption capacity of \u223c117.6 mg g\u22121 for As(V) and 184.2 mg g\u22121 for Cr(VI), which is mainly attributed to the large specific surface area and hierarchical structures of Fe3O4@NiO hierarchical microspheres. This work provides a promising approach for the design and synthesis of multifunctional microspheres, which can be used for water treatment, as well as having other potential applications in a variety of biomedical fields including drug delivery and biosensors.

Retracted: Yes

PubPeer comments:
 Figure 4 C showing  Fe3O4@NiO hierarchical microspheres is identical (90 degrees rotated) to Figure S4 B showing  Fe3O4@NiAl-LDH microspheres synthesized without a SiO2 layer in supporting information for different paper: https: doi.org 10.1021 ja2086323 Two papers seem to have different authors list and different affiliations. ![file] , 
 Fig. 1 XRD patterns of Fe3O4 microspheres (a), flowerlike Fe3O4@NiO hierarchical microspheres obtained by calcining precursors at 350 uC for 2 h. The precursors prepared at 160 uC for (b) 2 h, (c) 4 h and (d) 8 h XRD patterns are nearly identical 30 degrees but different for lower angles. ![file] , 
 Perhaps this retraction on another paper overlapping authors is indicative of the seriousness of these concerns: The first author  requested to retract this article because he admitted that Photoshop technology was used in the preparation of Fig. 1.  https: pubpeer.com publications CC963D5EE7150BC4B6FF5C020BE0E3#2 , 
 Retracted, [11 August 2021] . --------------------------- The Royal Society of Chemistry, with the agreement of the named authors, hereby wholly retracts this RSC Advances article due to concerns with the reliability of the data in the published article. The authors requested to retract this article because they admitted that the TEM characterization of the Fe3O4@NiO hierarchical microspheres in Fig. 4c was duplicated from the characterization of Fe3O4@NiAl-LDH microspheres in Fig. S4B from a J. Am. Chem. Soc. paper by Mingfei Shao et al. without permission.1 The authors would like to apologise to the authors of ref. 1, and for any inconvenience to readers. Signed: Shouwei Zhang, Jiaxing Li, Jinzhang Xu and Xiangke Wang Date: 11th August 2021 Tao Wen was contacted but did not respond Retraction endorsed by Laura Fisher, Executive Editor, RSC Advances , 
 Fig 5,  FESEM images of the obtained flowerlike Fe3O4@NiO hierarchical microspheres at various reaction durations: **(A) 1 h; (B) 2 h**; (C) 4 h and (D) 8 h. Panels A and B overlap, and probably do not represent materials formed after different reaction durations. ![file] Yes, the paper is already retracted, but perhaps it is still worth examining it, to learn what kind of problem might appear elsewhere. ,