Study On Adsorption Properties Of Cellulose-Modified MXene-based Composites For Nuclide Ions And Dyes

Due to the adjustable interlayer distance,abundant surface functional groups and hydrophilicity,MXenes have entered people’s field of vision in recent years as a new class of two-dimensional nanomaterials.At the same time,they can be used as materials for effectively removing various pollutants in wastewater and applied in the field of environmental remediation.MXenes have excellent surface functional group tunability,chemical compatibility,and compositional flexibility,thereby resisting damage induced in aqueous environments.they are therefore considered to have potential as ideal candidates for the removal of a large number of pollutants.adsorbent.This paper mainly reported two kinds of adsorption materials prepared:cellulose/silsesquioxane covalently modified MXene and cellulose/MXene/polyvinyl alcohol composite membrane,which were respectively applied to removal of uranyl ions and methylene blue（MB）dye in sewage.The work was as follows:（1）Polyhedral oligomeric silsesquioxane（POSS-OH）and hydroxypropyl cellulose（HPC）covalently modified Ti₃C₂T_x MXene（CHMP）with adjustable interlayer spacing was successfully synthesized.X-ray diffraction（XRD）results showed that linear HPC was more favorable for intercalation between Ti₃C₂T_x MXene layers compared with the nano-sized POSS-OH.After the covalent modification,the average interlayer spacing of Ti₃C₂T_x can reach 1.18 nm,providing 35.08%enhanced adsorption capacity.X-ray photoelectron spectroscopy（XPS）indicated high chemical stability of CHMP.Study on the incubation time of U（VI）showed that U（VI）can be quickly adsorbed and reach equilibrium within 90 minutes.Langmuir isotherm indicated that the adsorption mechanism of CHMP to U（VI）was the monolayer adsorption.The maximum adsorption capacity obtained by data fitting was about 307.67 mg g^-1.The mixed ion adsorption experiment demonstrated that CHMP has excellent selectivity to U（VI）compared with Co（II）,Sm（III）,Gd（III）,Ce（III）,Yb（III）,Nd（III）,La（III）,and Th（IV）.Furthermore,XPS and simulation results indicated that the adsorption and binding of UO₂²⁺on the surface of Ti₃C₂T_x MXene and HPC were strong binding with binding energy greater than7500 kcal/mo L,while POSS-OH was mainly used to improve the interlayer spacing.The coordination and electrostatic interaction contributed the most during the binding process.（2）A porous adsorbent（C-CMP）containing cellulose nanocrystals（CNC）,Ti₃C₂T_xMXene and polyvinyl alcohol（PVA）was prepared by a simple and environmentally friendly foaming method.Glutaraldehyde was used as crosslinker to improve outstanding mechanical property and boost adsorption efficiency of methylene blue（MB）molecules.Fourier transform infrared（FTIR）and thermogravimetric analysis（TGA）further confirmed that preparation of C-CMP foam and crosslinking reaction were successful.Scanning electron microscope（SEM）indicated that the macropores were distributed homogeneously.Adsorption experiment showed that maximum adsorption capacity of MB can reach 239.92 mg g^-1 which was much higher than anionic dye(methyl orange,45.25 mg g^-1).The adsorption behavior fitted well with Langmuir isotherm and pseudo-second-order kinetic models.Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic.Based on FTIR and X-ray photoelectron spectroscopy（XPS）analysis,the adsorption mechanism between C-CMP and MB molecules was attributed to electrostatic interaction.