Synthesis Of Modified Lignin-based Hollow Microspheres And Exploration Of The Forming Mechanism

With the increasing depletion of fossil,the efficient utilization of renewable lignocellulose biomass is becoming increasingly important.Lignin,the second most abundant biomacromolecule next to cellulose,is a phenolic polymer derived primarily from phenylpropanoid units,specifically syringyl(S),guaiacyl(G),and p-hydroxyphenol(H)monomers.Most lignin is produced as a side product in pulping industries and biorefineries,commonly used as a heat source or as a fertilizer.Thus,it have great theoretical significance and application value to explore its higher value-added functional materials to replace non-renewable fossil fuels.In this study,magnetic lignin spheres were successfully fabricated using the self-assembly method and explored the formation mechanism,Lignin hollow mocrospheres were successfully fabricated using the self-assembly,and the magnetic lignin spheres were fabricated by introducing Fe3O4 nanoparticles in order to recover easily adsorbents.The adsorption capacities of the lignin hollow microspheres were evaluated by the adsorption of organic dyes.Meanwhile,the assembly mechanism of lignin hollow microspheres formation can be deduced by changing the molecular weight,monomer-unit structure and hydrophilic/hydrophobic block ratio of the lignin.The main conclusions of this paper are as follows:(1)Lignin hollow microspheres were successfully fabricated using the self-assembly in the THF solution.The SEM results showed that the lignin hollow microspheres from larch exhibited perfect chaplet-like spherical shape but that from poplar partially collapsed.Moreover,the magnetic lignin spheres were also successfully fabricated by introducing Fe3O4 nanoparticles,and they could be easily separated from the effluent by introducing an external magnetic field.(2)The adsorption capacities of the lignin hollow microspheres 'were evaluated by the adsorption of organic dyes.The results show that the larch and poplar magnetic lignin spheres had respective values of the maximum adsorption capacities of 31.23 and 25.95 mg/g for methylene blue,respectively.The adsorption kinetics and adsorption isotherm were agreed well with the pseudo-second-order and Langmuir model,respectively.Meanwhile,after three cycles of desorption,the removal efficiencies of the organic dyes still could reach more than 96%.(3)The reagents have been used to hydrophobic modification and research the assembly mechanism of lignin hollow microspheres formation.Different lignin aggregates and are obtained from the different modified lignin samples,which have the different molecular weight,different phenylpropanoid units' structure and different hydrophilic/hydrophobic block ratio.We also proposed the assembly mechanism of lignin hollow microspheres formation.