Preparation Of Porous Cellulose Triacetate Composite Microspheres Modified With Lignin/Polydopamine And Their Adsorption Properties

Cellulose is a natural polymer that can be subdivided into numerous derivatives depending on its structure.Cellulose triacetate（CTA）,a highly esterified cellulose derivative,is widely used in pharmaceutical,chemical and textile applications due to its low toxicity qualities and stable molecular structure.However,the application of CTA is limited in the field of adsorption due to its poor chelating properties to metal ions.In this thesis,cellulose triacetate and sodium lignosulfonate were dissolved in solvent for co-blending,and porous cellulose triacetate/lignin composite microspheres（PCLM）were prepared by the emulsification-solvent evaporation method;porous magnetic cellulose triacetate/lignin composite microspheres（PMCLM）were prepared by encapsulating Fe₃O₄,which were applied to the adsorption of Cu²⁺;porous cellulose triacetate/polydopamine composite microspheres（PCM-PDA）were prepared by oxidative autopolymerisation of dopamine on the surface of the substrate material and applied to the adsorption of Cu²⁺and Ag⁺.In this paper,the structures of porous cellulose triacetate microspheres（PCM）,PMCLM and PCM-PDA were characterized by various modern detection and analysis methods such as FTIR,XRD,XPS,SEM,TGA,etc.The SEM and BET results confirmed that the prepared composite microspheres were spherical with homogeneous pore size and a large number of micropores on the surface and inside.XRD and TGA results confirmed the good magnetic responsiveness of PMCLM and the significant changes in the physical structure of the modified composite microspheres,with a significant decrease in crystallinity.In this paper,adsorption experiments were carried out at 298.15 K.The results showed that:the adsorption amount of adsorbed Cu²⁺reached 48.44 mg/g at pH=5,PMCLM at a dose of 0.2 g/100 m L and initial concentration of Cu²⁺of 100 mg/L for 90 min;The adsorption of Cu²⁺reached 38.51 mg/g at pH=5,PCM-PDA with a dose of 0.2 g/100 m L,an adsorption equilibrium time of 150 min and an initial Cu²⁺concentration of 80 mg/L.The adsorption capacity of the adsorbed Ag⁺was 59.51 mg/g at a solution pH=6,PCM-PDA dosing at 0.2 g/100 m L,an adsorption equilibrium time of 40 min and an initial Ag⁺concentration of 120 mg/L.The adsorption of Cu²⁺by PMCLM and the adsorption of Cu²⁺and Ag⁺by PCM-PDA were in accordance with the quasi-secondary kinetic model and the Langmuir adsorption isotherm model,controlled by chemisorption,and had monomolecular layer adsorption characteristics.The adsorption thermodynamic results verified that the adsorption of modified porous cellulose triacetate composite microspheres proceeded spontaneously,possessing characteristics of heat absorption and disorderly increase,and the adsorption capacity was highest at 318.15 K.PMCLM and PCM-PDA also possessed certain adsorption capacity after more than three desorption-adsorption cycles.It was shown that the modification of cellulose triacetate microspheres by sodium lignosulfonate and polydopamine led to a significant improvement in the adsorption performance of the modified cellulose triacetate composite microspheres for Cu²⁺and Ag⁺,and they have the prospect to be used as adsorbent materials.