Preparation Of Bacterial Cellulose-based Functional Nanofibrous Membrane And Study On Its Ion Adsorption Performance

Bacterial cellulose is an ideal ionic adsorption material due to a series of properties such as its strong hydrophilicity,biodegradability and a large number of hydroxyl functional groups.However,the structural relationship of bacterial cellulose limits its application in the field of adsorbent materials,so the composite of BC with other adsorbent materials to obtain bacterial cellulose-based functional nanofibrous membrane is considered as an effective solution.In this thesis,naturally degradable BC was prepared by biological culture method and used as a substrate material,and PDA and UiO-66-NH₂were used as adsorbent materials to compound with BC to prepare two different bacterial cellulose-based functional nanofibrous membranes,and the morphology of the prepared nanofibrous membranes was regulated and characterized.The adsorption effects of the two materials on Fe³⁺,Cu²⁺and Cd²⁺were also tested,and the effects of p H value,initial concentration and adsorption time on the adsorption performance were investigated,and the adsorption mechanism was elucidated.The specific research of the thesis is as follows:（1）Environmentally friendly bacterial cellulose material was prepared by bioculture method,and BC@PDA composite nanofibrous membrane was prepared by using the mussel-like properties of PDA material to load it on the fiber surface of BC.The adsorption performance of BC@PDA composite nanofibrous membrane was tested to investigate the effects of p H value and adsorption time on its adsorption performance,and to elaborate its adsorption mechanism.The results showed that the optimal adsorption p H of BC@PDA composite nanofibrous membrane was 3.0,5.0 and 6.5 for Fe³⁺,Cu²⁺and Cd²⁺solutions,respectively,and the adsorption equilibrium time was 140 min,and the adsorption amounts were 110.57 mg/g,67.26 mg/g and 65.84 mg/g,respectively,While the adsorption amounts of BC on Fe³⁺,Cu²⁺and Cd²⁺solutions were 46.65mg/g and 15.87 mg/g and 14.81 mg/g,respectively,and the adsorption amounts of BC on Fe³⁺,Cu²⁺and Cd²⁺solutions were enhanced by 137%,324%and 345%,respectively,after loading PDA.Model fitting of the adsorption of BC@PDA composite nanofibrous membranes was performed,and the fitting results showed that the adsorption of BC@PDA composite nanofibrous membranes fitted better with the quasi-secondary kinetic model,while in the isothermal adsorption model fitting,better results were obtained with the Freundlich isothermal adsorption model,indicating that the adsorption consisted mainly of chemisorption of multimolecular layers.Finally,the reusability performance of BC@PDA composite nanofibrous membrane was investigated,and it was found that the adsorption capacity remained above 50%after three cycles of use,indicating that the BC@PDA composite nanofibrous membrane has certain reusability performance.（2）The UiO-66-NH₂/BC composite nanofibrous membranes were prepared by solvent thermal method using the self-made BC and modulated the crystal growth morphology to investigate the differences of the UiO-66-NH₂/BC composite nanofibrous membranes prepared by loading the BC with different growth morphologies.The best UiO-66-NH₂/BC-3 composite nanofibrous membranes were prepared by adding acetic acid for crystal morphology modulation based on SEM,TEM and mechanical properties analysis.The adsorption performance of UiO-66-NH₂/BC-3 composite nanofibrous membranes was also investigated,the results showed that the optimal adsorption p H values of UiO-66-NH₂/BC-3 composite nanofibrous membranes were 3.0,5.0 and6.5 for Fe³⁺,Cu²⁺and Cd²⁺,respectively,and the adsorption equilibrium time was 10 h.The adsorption amounts were 127.27 mg/g,114.34 mg/g and 83.66 mg/g,respectively.The adsorption amounts of Fe³⁺,Cu²⁺and Cd²⁺by pure BC nanofiber membranes were 44.26 mg/g,36.50 mg/g and20.92 mg/g,respectively,and the loading of UiO-66-NH₂increased the adsorption amounts of Fe³⁺,Cu²⁺and Cd²⁺by 188%,213%and 300%,respectively,compared with those of pure BC.The loading of UiO-66-NH₂resulted in a significant increase in the adsorption capacity of BC up to more than twice.By fitting the adsorption behavior of UiO-66-NH₂/BC-3 composite nanofibrous membranes,it was found that the adsorption of UiO-66-NH₂/BC-3 composite nanofibrous membranes fit better with the quasi-secondary kinetic model compared to the quasi-first-order kinetic model in the kinetic model fit,while the Langmuir isothermal adsorption model fit gave better results in the isothermal adsorption model fit,indicating that the adsorption of UiO-66-NH₂/BC-3 composite nanofibrous membranes is a single-molecule layer chemisorption-based adsorption.The adsorption rate of the adsorbent was maintained above 50%after three adsorption-desorption cycles,indicating that the adsorbent has some reusable performance.In summary,in this thesis,naturally degradable BC was prepared by biological culture method,and two different bacterial cellulose-based functional nanofibrous membranes were prepared by modifying BC separately,and the adsorption properties of the two bacterial cellulose-based functional nanofibrous membrane materials were investigated.The results showed that the two materials have good adsorption properties for Fe³⁺,Cu²⁺and Cd²⁺,and have some reusable properties.