Preparation Of Porous Carbon Microspheres By Chitosan And Their Adsorption Properties

Chitosan,a natural alkaline polysaccharide is next to the most abundant natural cellulose,which obtained by the deacetylation of chitin.Chitosan has many advantages,such as good adhesion,biodegradability,biocompatibility,excellent adsorbability and innocuity.It has been widely applied in many fields,such as food preservation,environmental protection,medicine and sewage treatment.Porous carbon,a inorganic and nonmetallic material with abundant pore structure,has good application prospects in sewage treatment and other fields due to its super surface area,acid and alkaline resistance.However,most of the porous carbon in the practical process has caused the problems of the aggregation of adsorbents,the blockage of the equipment and the difficult separation of solid from liquid because of the small volume of the porous carbon.Therefore,the aim of this research is to prepare porous carbon microspheres with porous structure,large specific surface,good adsorption performance and convenient recovery,by using chitosan as raw material and combining with yeast or magnetic iron oxide.The chitosan/yeast composite carbon microspheres and Fe3O4@chitosan micro-beads were applied to the antibiotic adsorption treatment,and the regeneration properties of Fe3O4@chitosan microspheres were also investigated.The main research contents are listed as follows:?1?chitosan/yeast composite carbon microspheresA novel porous carbon sphere with pomegranate-like internal structure was synthesized by using chitosan wrapping yeasts?CWY?as precursor via thermal cracking under 400?.The resultant CWY composite carbon microspheres were characterized by scanning electron microscope?SEM?,X-ray diffraction?XRD?and Fourier transform infrared spectroscopy?FT-IR?,respectively.The polarity property of CWY carbon sphere was explored,too.Boehm titration was involved to determine the contents of acidic groups on the surface of CWY carbon sphere.The results showed the uniform distribution of internal yeasts carbon which had amorphous and porous structure.Polarity test showed that CWY carbon sphere had a higher dispersion capacity in non-polar dissolvent.The contents of surface acidic groups on CWY carbon sphere was 3.281mmol?g^-1.The adsorption capacity of CWY carbon spheres were compared with CTS carbon spheres using doxycycline as an adsorbate under alkaline condition?pH=10?.The CWY carbon sphere showed a higher adsorption capacity.The equilibrium data of CWY carbon sphere fitted well with the Langmuir isothermal model,and the maximum theoretical adsorption capacity of CWY carbon sphere for doxycycline was 3.07 mg?g^-1.?2?Magnetic Fe₃O₄@chitosan Carbon Micro-beads:Removal of Doxycycline form Aqueous Solutions and Heterogeneous Fenton-like RegenerationThe adsorptive removal of antibiotics from aqueous solutions is recognized as the most suitable approach due to its advantages of easy operation,low cost,nontoxic properties and high efficiency,however,the conventional regeneration of saturated adsorbents make it become an expensive and time-consuming process for water treatment.Herein,the magnetic Fe₃O₄@chitosan carbon micro-beads?MCM?were successfully prepared by wrapping Fe₃O₄ nanoparticles into chitosan hydrogel via an alkali gelation-thermal cracking process.The products of MCM composite microspheres were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,Fourier transform infrared spectroscopy?FTIR?and N₂ adsorption/desorption curves?BET curves?.A possible mechanism for the formation of MCM products had been proposed on the basis of above characterization methods.The potential applications of MCM for the adsorptive removal of doxycycline?DC?from aqueous solutions was evaluated using a fixed-bed column to investigate the effects of various factors,such as pH?2-11?,initial concentration?20-30mg/L?,flow rate?1.1-3.1mL/min?,and bed depth?0.8-1.6 cm?on breakthrough time and adsorption capacity.The results showed that all the factors had a significant effect on the adsorption capacity of DC?increase with the increase of pH values and the bed depth,decrease with the increase of initial concentration and flow rate?.The Thomas and Yoon-Nelson models showed a good agreement with the experimental data and could be applied for the prediction of the fixed-bed column properties and breakthrough curves.More importantly,the saturated bed was readily in situ regenerated by using H₂O₂ solution to trigger a heterogeneous Fenton reaction.The synergistic function originating from the combination of the absorption features of chitosan carbon with the excellent magnetic and catalytic properties of Fe₃O₄ nanoparticles result in a promising composite material for wastewater treatment.