Preparation Of Nanofibrillated Cellulose/Carbon Quantum Dots Composite Aerogels And Research Of Metal Ion Adsorption Properties

With the deterioration of the natural environment and the development of the industrialization process,cellulose has received wider attention due to its green and environmental protection characteristics.However,in actual production and life,a considerable part of the wood processing residues containing lignocellulose are discarded as industrial waste without efficient use,resulting in a waste of resources.On the other hand,with the rapid development of the chemical industry,a considerable portion of toxic and harmful pollutants are discharged into the natural water environment without further treatment,causing great harm.Among these water pollutants,heavy metal ions have become one of the important pollutants in water because of their various types,great toxicity,and difficulty in handling.Therefore,the development of new green and environmentally friendly biomass-based heavy metal ion adsorption materials is an effective and feasible way to solve resource waste and water pollution.Therefore,in this paper,lignocellulose is separated from wood and processed into nanocellulose(NFC)by chemical/physical means.Carbon quantum dots(CQDs)and NFC aerogels are reasonably prepared using NFC as the initial material.And NFC/CQDs composite aerogels.Specific research work is as follows:(1)Using natural poplar wood powder as a raw material,the extracts,hemicellulose and lignin inside the wood are sequentially removed by chemical treatment,and then NFC water is successfully prepared by combining TEMPO pre-oxidation and high-intensity ultrasound The suspension was used as a raw material,and ethylenediamine was used as a nitrogen doping source to prepare a green non-toxic lignocellulose-based nitrogen-doped fluorescent carbon quantum dot.The structural characterization of the prepared carbon quantum dots was performed by various advanced characterization methods,and the fluorescence intensity of the carbon quantum dots in different concentrations of heavy metal ion solutions was tested.The results show that the carbon quantum dots prepared by using NFC aqueous suspension as the raw material have good physical and chemical properties,the sample size is uniform,the aqueous solution is stable and can emit obvious blue-green fluorescence under 365nm ultraviolet excitation and the heavy metal ion Cr6+ is also obvious.The fluorescence response decreases when the concentration increases.(2)NFC aerogels with different solid contents were prepared by freeze-drying.The effects of different solid contents on the properties of NFC aerogels were explored through morphological analysis and specific surface area and porosity testing.The results show that too high or too low concentration will have a negative impact on the performance of NFC aerogels.When the concentration is too high,the specific surface area is lower and there are fewer pores,which is not conducive to the investigation of its adsorption performance.Low strength,easy to break and crack,and difficult to carry out experiments.(3)The NFC aerogel is used as the skeleton structure,carbon quantum dots are added to the NFC aqueous suspension,and then the NFC/CQDs composite aerogel is prepared by freeze-drying.The single ion solution is used to simulate metal ion pollution in water for adsorption.The properties of the composite aerogel structure were characterized by various advanced testing and analysis methods,and its adsorption kinetics and visualization possibilities were explored.The results showed that the composite aerogel successfully retained the three-dimensional network structure of the NFC aerogel,and successfully dated the carbon quantum dots with fluorescent properties,giving them new fluorescent properties.At the same time,compared with NFC aerogels,composite aerogels have a large number of complex and more complex pore structures,the ratio increased by 22%,and the decrease decreased by 42.9%.Changes in pH will affect the entire adsorption process,and different types of carbon quantum dots can be quenched.All heavy metal ions have better adsorptivity,but for some light metal ions are not so good,so it can be used as a selective adsorbent.The kinetic analysis of the adsorption process of the composite aerogel shows that it is mainly chemical adsorption.The adsorption rate and effect are accompanied by the analysis and fitting of the fluorescence performance and the adsorption performance.It shows that the adsorption amount of the composite aerogel increases during the adsorption process.The fluorescence intensity is weakened and negatively correlated with each other.It is shown through the function fitting that it has a better functional relationship.The adsorption effect can be detected by the fluorescence intensity of the composite aerogel to achieve visual adsorption performance.