The selective adsorption performance and mechanism of multiwall magnetic carbon nanotubes for heavy metals in wastewater

Zhongbing Wang,Kai Zhou,Hui Liu,Wenbin Xu,Fanghui Jie,Zongwen Zhao

doi:10.1038/s41598-021-96465-7

Zhongbing Wang, Kai Zhou + Show 4 more

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https://doi.org/10.1038/s41598-021-96465-7

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Abstract

The safe treatment of heavy metals in wastewater is directly related to human health and social development. In this paper, a new type of recyclable adsorbent is synthesized through the oxidation of enhancer and modification with magnetic nanoparticles. The new adsorbent not only inherits the advantages of multiwall carbon nanotubes (6O-MWCNTs), but also exhibits a new magnetic property and further improved adsorption capacity, which is conducive to the magnetic separation and recovery of heavy metals. The adsorption results indicate that multiwall magnetic carbon nanotubes (6O-MWCNTs@Fe3O4) have a good performance for Pb(II) selective adsorption, with a maximum adsorption capacity of 215.05 mg/g, much higher than the existing adsorption capacity of the same type of adsorbents. Under the action of an external magnetic field, 6O-MWCNTs@Fe3O4 that adsorbed metal ions can quickly achieve good separation from the solution. The joint characterization results of FTIR and XPS show that under the action of both coordination and electrostatic attraction, the C=O bond in the –COOH group is induced to open by the metal ions and transforms into an ionic bond, and the metal ions are stably adsorbed on the surface of 6O-MWCNTs@Fe3O4. Pb(II) has a stronger attraction than Cu(II) and Cd(II) to the lone pair of electrons in oxygen atoms to form complexes, due to the covalent index of Pb (6.41) is more larger than that of Cu (2.98) and Cd (2.71).These data provide a new type of recyclable adsorbent for the efficient treatment of heavy metal ions in wastewater and enrich relevant theoretical knowledge.

Highlights

The safe treatment of heavy metals in wastewater is directly related to human health and social development
X-ray diffraction (XRD) was used to resolve the phase and crystal changes of 6O-multi-walled carbon nanotubes (MWCNTs) after magnetic grafting, and the results are shown in Fig. 1. 6O-MWCNTs have two typical characteristic peaks, which are located at 25.9° and 43.6°, and are consistent with those reported in the literature[19]
The XRD, Fourier-transform infrared spectroscopy (FTIR) and SEM results indicate that carboxyl functional groups (–COOH) and magnetic groups (Fe–O) are effectively introduced on the surface of the obtained 6O-MWCNTs@Fe3O4. Fe3O4 particles are evenly distributed on the surface of the 6O-MWCNTs structure

Summary

Introduction

The safe treatment of heavy metals in wastewater is directly related to human health and social development. Pb(II) has a stronger attraction than Cu(II) and Cd(II) to the lone pair of electrons in oxygen atoms to form complexes, due to the covalent index of Pb (6.41) is more larger than that of Cu (2.98) and Cd (2.71) These data provide a new type of recyclable adsorbent for the efficient treatment of heavy metal ions in wastewater and enrich relevant theoretical knowledge. CNTs have high efficiency in adsorbing and removing metal ions, but they are difficult to separate from aqueous solutions due to their small size, and are discharged into the water environment, causing secondary pollution[21]. Changes in the microscopic morphology of 6O-MWCNTs before and after modification were analyzed by scanning electron microscope and transmission electron microscope (SEM-TEM)

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Conclusion