Preparation And Sorption Properties Of Cellulose Nanofiber Based Composites

In recent years,with the rapid development of the economic level and the rapid improvement of human living standards,the problem of water pollution has become increasingly prominent.And the industrial wastewater is the most important cause of water pollution.Industrial wastewater contains a large number of heavy metal ions such as nickel,cadmium,copper.These heavy metal ions are highly toxic,difficult to degrade and easy to enrich,which seriously threatens the health of animals,plants and humans.Therefore,the treatment of heavy metal pollution in water is a serious and urgent task to protect ecological environment and human health.In this paper,banana peel was used as raw materials to prepare amininated magnetic cellulose nanofibers（PEI-CNFs@Fe₃O₄）and cellulose nanofibers/chitosan（CNFS/CS）composites by the glutaraldehyde cross-linking method and the freeze-drying method.The structures of PEI-CNFs@Fe₃O₄ and CNFS/CS were characterized by scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FT-IR）and X-ray photoelectron spectroscopy（XPS）.At the same time,the effects of p H,temperature and sorption time on the sorption of heavy metal ions on PEI-CNFs@Fe₃O₄ and CNFS/CS were studied by static batch experiments.The sorption kinetics,sorption isotherm and thermodynamics of PEI-CNFs@Fe₃O₄ and CNFS/CS towards heavy metal ions were studied.The main conclusions were as follows:（1）Two kinds of composites,PEI-CNFs@Fe₃O₄ and CNFS/CS,were successfully prepared,and the sorption capacities of heavy metal ions were greatly improved.（2）The structures of PEI-CNFs@Fe₃O₄ and CNFS/CS were characterized by modern analytical methods such as Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy.The results indidated that,compared with CNFS,both PEI-CNFs@Fe₃O₄ and CNFS/CS introduced amino groups.（3）The sorption isotherm and kinetic fitting results showed that the sorption of heavy metal ions on PEI-CNFs@Fe₃O₄ and CNFS/CS conformed to the Langmuir isotherm model and the pseudo-second-order kinetic model,indicating that the sorption process was mainly monollayer chemisorption.（4）The sorption mechanisms of modified CNFs towards divalent heavy metal ions were mainly complexation and ion exchange,with a small amount of electrostatic attraction.In this study,used agricultural waste banana peel as the raw material,and two kinds of composites were obtained by simple preparation process,which showed good sorption performance of heavy metal ions in wastewater,and achieved the purpose of"treating waste with waste".