Abstract
Due to hollow and tubular structure, a natural kapok fiber (KF) was used as the support and orientation matrix to control the polymerization of ethyleneglycol dimethacrylate (EGDMA) and N-vinylimidazole (VIM) along its inherent axial surface via a facile in situ rapid polymerization reaction in air atmosphere. The as-formed KF@VIM/EGDMA composite is featured with porous surface and rich N-containing functional groups for potential application as a highly efficient adsorbent for removal of toxic Hg(II) from aqueous solution. The variables affecting the adsorption capacity were studied, including monomer ratio, external pH values, contact time, and initial Hg(II) concentration. The pseudo-second-order equation and two adsorption isotherms including Langmuir and Freundlich equations were applied to determine the adsorption kinetics and adsorption capacity. The results show that the as-prepared KF@VIM/EGDMA composite has a maximum adsorption capacity of 697 mg/g to Hg(II), while no appreciable adsorption capacity can be found for KF itself. Given its intrinsic large lumen, faster adsorption kinetics (45 min) are also expected and observed for KF@VIM/EGDMA. After a simple filtration, this adsorbent can be directly separated from the aqueous solution and then be regenerated for multi-cyclable utilization. During the adsorption process, the chemical complexing represents the main adsorption mechanism. As a naturally renewable KF, such a simple preparation method opens a new avenue to develop highly efficient and economically viable adsorbent for removal of toxic heavy metal from aqueous solution.
Highlights
Owing to high surface-to-mass ratio, bio-compatibility, good mechanical performance and ability to be shaped in various forms, many natural or man-made microfibers have been directly utilized or modified as an ideal substrate material for loading active nanoparticles (El Ghali et al, 2012; Xia et al, 2013)
With the proceeding of polymerization reaction, the surface of kapok fiber (KF) was coated by a thin layer of polymer coating consisted of P(VIM-co-ethyleneglycol dimethacrylate (EGDMA)), as shown in Scheme 1
Compared the pHIEP with pHPZC, the equal value of them would indicate the similar positively charged external surface and the interior of KF@VIM/EGDMA, suggesting that the inner wall of KF was coated with polymer layer
Summary
Owing to high surface-to-mass ratio, bio-compatibility, good mechanical performance and ability to be shaped in various forms, many natural or man-made microfibers have been directly utilized or modified as an ideal substrate material for loading active nanoparticles (El Ghali et al, 2012; Xia et al, 2013). 0.8–1.0 μm in wall thickness) (Chung et al, 2008) with the hollow rate of above 86% (Kang et al, 2007), this fiber shows its potential for various new application fields, especially as the support for active nanoparticles and as the biotemplate to prepare a series of microtubes originated from organic or inorganic materials (Zheng et al, 2014). KF is an insoluble natural polymer with a hollow and large lumen, and it is anticipated to guide the growth orientation of a polymerizable monomer to avoid the agglomeration of polymer and enlarge the specific surface. The orientated growth of a polymerizable monomer on the surface of KF can afford the resulting material with tailored functional groups for promising application as an excellent adsorbent for removal of a targeted pollutant
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