Abstract
Amino-thiol bifunctional polysilsesquioxane/carbon nanotubes (PSQ/CNTs) magnetic composites were prepared by sol-gel method with two types of functional siloxanes coating on carboxyl CNTs simultaneously. The composites were served as efficient adsorbents for removing Hg(II) in aqueous solution and the adsorption properties were investigated systematically. The optimal pH of bifunctional composites for Hg(II) removal is at pH 4.5. The thermodynamic fitting curves are more consistent with the Langmuir model and the adsorption capacities of the bifunctional composites for Hg(II) varied from 1.63 to 1.94 mmol g−1 at 25°C according to the Langmuir model. The kinetics curves are more fitted to the pseudo-second-order model and the composites could selectively adsorb Hg(II) in a series of binary metal ions solution. The elution regeneration tests showed that the adsorption rate could still reach 78% after repeat cycle three times. It is expected that the bifunctional PSQ/CNTs magnetic composites can be potentially applied to remove low concentration Hg(II) from waste water.
Highlights
Environmental problems caused by harmful pollutants have become serious threats to the survival of human beings and other living things (Hsu et al, 2021; Wang et al, 2021), and water pollution is prominent among them
The composites were applied to recycle Au(III) from wastewater and the results indicated that the bifunctional PSQ/Carbon nanotubes (CNTs) magnetic composites have excellent performances in adsorbing Au(III)
The static adsorption indicates that the bifunctional PSQ/CNTs magnetic composites have superior adsorption capacities than monofunctional composites, pristine material CNTs-COOH@Fe3O4, and common intermediate CNTs-APTMS@Fe3O4, the adsorption capacities increase 0.3–0.9 mmol g−1 to different extent compared to unfunctional materials
Summary
Environmental problems caused by harmful pollutants have become serious threats to the survival of human beings and other living things (Hsu et al, 2021; Wang et al, 2021), and water pollution is prominent among them. Common water pollutants include inorganic pollutants like heavy metal ions, acid, alkali and salt, and other organic pollutants (Mudasir et al, 2020, Wang et al, 2020a; Zhangal and Zhang, 2020) stem from metallurgy, chemical fiber, papermaking, printing and dyeing, and other industrial wastewaters (Khan et al, 2021; Verma and Balomajumder, 2020). Adsorption is more attractive in removing metal ions than chemical precipitation, sedimentation, ion exchange, filtration, and other traditional means (Zhao J. et al, 2018; Liu et al, 2019; Zhang B. et al, 2019), thanks to its simple operation, less secondary pollution, high adsorption efficiency, low cost, and other advantages (Zhao et al, 2012; Wang et al, 2017; Yang et al, 2019).
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