Abstract
Birnessite nanoflowers composed of layers have been proven to be the strongest adsorbent and oxidant in the surface environment. However, the current synthesis methods of birnessite nanoflowers are suffering from long reaction time and high reaction temperature. Based on these, this paper explores a new method for the rapid and controlled synthesis of layered manganese oxides. The method relies on the molar ratios of KMnO4 and H2O2 redox reacting species to drive the production of birnessite nanoflowers under acidic conditions. The molar ratios of KMnO4 and H2O2 are the key to the crystal structure of the as-prepared. It was found that when the molar ratios of KMnO4 and H2O2 is from 1:1.25 to 1:1.90, the sample is birnessite nanoflowers, and when the ratio is increased to 1:2.0, the sample is a mixture of birnessite nanoflowers and feitknechtite nanoplates. Among the as-prepared samples, BF-1.85 (molar ratios of KMnO4 and H2O2 is 1:1.85) shows the highest capacity for Pb2+ adsorption (2,955 mmol/kg) and greatest degradation efficiency of phenol and TOC. The method proposed herein is economical and controllable, and it yields products with high efficiency for the elimination of inorganic and organic pollutants.
Highlights
The physical and chemical properties of materials are discrepant when they show different morphologies (Li et al, 2020a; Li et al, 2020b)
Upon increasing the KMnO4/H2O2 molar ratio to 1:2, the manganese oxide products show the (002) and (006) planes of feitknechtite (JCPDS: 18-804), as well as the (100) and (110) plane of birnessite. These results indicate that the materials produced with the ratio to 1:2 KMnO4/ H2O2 reaction mixtures are composed of both feitknechtite and birnessite
The disappearance of the (001) and (002) diffraction peaks is considered to be an important distinctive feature between feitknechtite and birnessite (Post, 1999; Villalobos et al, 2003). These results prove the phase transition of birnessite begins with KMnO4/H2O2 of 1:2
Summary
The physical and chemical properties of materials are discrepant when they show different morphologies (Li et al, 2020a; Li et al, 2020b). Three-dimensional (3D) hierarchical structures assembly by 1D or 2D nanoscale as building blocks, such as nanosheets, nanoparticles, nanorods, and nanoplates have attracted much attention in recent years (Li et al, 2013; Liao et al, 2013; Wang et al, 2014; Li et al, 2020d; Li et al, 2020e) This is due to the 3D hierarchical architectures inherits the superior properties of nanoscale building blocks, and obtains additional benefits from the unique secondary structure (Yan et al, 2014; Li et al, 2021).
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