Controllable Synthesis Of Hollow Carbon Nanospheres And Their Application In Cr(Ⅵ) Removal

Hollow carbon nanospheres (HCS) have been widespread applied in many fields, such as catalyst support, electrode material, adsorbent and pharmaceutical carrier, etc, due to their high ratio of surface area to volume, adjustable particle size and shell thickness, antacid alkali resistance, good chemical stability and great thermal stability advantages. The scientific challenge is to synthesize HCS with controllable sizes and effectively use their cavities in the field of nanomaterials.In this paper, monodisperse hollow carbon nanospheres have been synthesized through confined nanospace pyrolysis. The influences of the hard-template sizes, the amount of precursors and creation of the confined nanospace (i.e. silica coating shell) on the structures of HCS were systematically investigated. Based on the utilization of the cavity of HCS, iron-based HCS (HCS/Fe) were fabricated by solution phase switchable transport of active iron species combined with solid state thermolysis technique, and the property of HCS/Fe and its performance on the removal of chromium ions were studied. The contents of this thesis is listed below:Part Ⅰ:Colloidal polystyrene spheres (PS) were synthesized by emulsion polymerization,which were then used as a hard-template later on. Phenolic resin (PF) coated PS composite nanospheres (PS@PF) were prepared by using phenol (P) and hexamethylenetetramine (HMT) as carbon precursors, via hydrothermal method. After coating PS@PF with a SiO2-layer as the confined shell and followed by confined nanospace pyrolysis, and silica removal procedure, monodisperse HCS can be achieved. The cavity size of HCS can be adjusted from190nm to330nm by varying the diameter of the PS template; the carbon shell thickness of HCS can be precisely tuned in the range30-80nm by controlling the molar ratio of phenolic resin and PS template. It has been verified that a dense SiO2-layer can cause increases in both the carbon yield and the shell thickness.Part Ⅱ:Magnetic hollow structures with microporous shell and highly dispersed active cores (Fe/Fe3C nanoparticles) have been rationally designed and fabricated using solution phase switchable transport of active iron species combined with solid state thermolysis technique, allowing selective encapsulation of functional Fc/Fc3C nanoparticles in the interior cavity making use of PS@PF as the initial material and Fe(NO3as iron source. These engineered functional materials (HCS/Fe) show high loading (～54wt%) of Fe.Part III:HCS/Fe showed an excellent chromium removal capability (100mg g-1), fast adsorption rate (8766mL mg-1h-1) and easy magnetic separation property (63.25emu g-1). During an adsorption process, the internal highly dispersed Fe/Fe3C nanoparticles supply a driving force for facilitating Cr(VI) diffusion inward, thus improving the adsorption rate and the adsorption capacity. At the same time, the external microporous carbon shell can also efficiently trap guest Cr(VI) and prevent Fe/Fe3C nanoparticles from corrosion and subsequent leaching problem.