The Preparation Of Nano-magnetic Chitosan And Its Adsorption Of Cu²⁺

In this paper,the preparation process of chitosan and nano-magnetic chitosan was optimized.The preparation of chitosan was optimized with NaOH mass fraction,water bath temperature,water bath time,and feed ratio of Pipi shell and NaOH solution.The preparation of nano-magnetic chitosan was optimized by ultrasonic time,amount of emulsifier,material ratio of chitosan and Fe3O4,and amount of crosslinking agent.The structure and performance was characterized by scanning electron microscope,thermogravimetric analyzer,infrared spectrometer and X-ray diffractometer.The optimum adsorption conditions of nano-magnetic chitosan for Cu2+ were studied by the dosage of nanometer magnetic chitosan,adsorption time,initial concentration of Cu2+and pH of Cu2+ solution and separation experiment of nano-magnetic chitosan.Adsorption kinetics fitting experiments and adsorption isotherm experiments were fitted to the adsorption of Cu2+ on nano-magnetic chitosan.The results showed that chitosan was prepared by soaking chitin in mass fraction 45%NaOH at a feeding ratio of 1:300(chitin mass and NaOH volume ratio g:mL),heated at 85? for 3h,then washed the chitosan to neutral and dry at room temperature.The prepared chitosan was with 9.0%of moisture content,0.4%of ash content,the degree of deacety-lation is 84.1%.The optimal preparation of nano-magnetic chitosan is as follows:the mass ratio of chitosan and Fe3O4 is 1:1.5(g:g),ultrasonic 90 min,emulsifier dosage is 7mL,crosslinking agent dosage is 4 mL,the removal rate of Cu2+ by nano-magnetic chitosan is 94.62%.Fourier transform infrared spectroscopy(FTIR)characterization showed that the nano-magnetic chitosan was successfully prepared.Scanning electron microscopy(SEM)showed that the nano-magnctic chitosan was a uniform spherical structure with uniform distribution,differential scanning calorimetry(DSC)and thermogravimetric analysis(Tg).The results showed that when the temperature was 451?,the bond between Fe3O4 and chitosan will be broken,The content of Fe3O4 in nano-magnetic magnetic chitosan is about 3 1.35%,the content of chitosan is about 64.66%,and the X-ray diffraction(XRD)spectrum showed that the crystal structure of Fe3O4 was not affected during the preparation of nano-magnetic chitosan,and the crystal phase of Fe3O4 was not changed and the diameter of nano-magnetic chitosan is about 75.82 nm.The adsorption experiment of Cu2+ showed that 0.5g nano-magnetic chitosan was added to 50mL 20?g/mL CuSO4 solution with pH=5 and adsorbed for 5h.The Cu2+removal efficiency was the highest,reaching 95.06%and the adsorption capacity is 20.62mg/g.The separation experiment showed that the separation of nano-magnetic chitosan was simple and the separation and recovery reached 84.76%.The adsorption kinetics of nano-magnetic chitosan showed that the adsorption of Cu2+ by nano-magnetic chitosan was consistent with the second-order kinetics of Pseudo,the saturated adsorption capacity of nano-magnetic chitosan to Cu2+ is 17.32mg/g.The experimental results of adsorption isotherm showed that the adsorption of Cu2+ by nano-magnetic chitosan was consistent with the Freundlic adsorption isotherm model,the Freundlich constant is 8.48mg1-1/nL1/n/g and the maximum adsorption capacity of nano-magnetic chitosan for Cu2+ is 213.68 mg/g.