| With the increasingly drying up of non-renewable fossil resources and the rapidlydeteriorated environmental problem of pulping spent liquor, the recycle and utilization oflignin from pulping spent liquor was increasingly important. The dispersing effects oflignin-based polymer on solid particles were mainly owing to its molecular structure andadsorption properties on solid particles. It was of great practical significance for theapplication of lignin and its ramifications to investigate the adsorption properties oflignin-based polymers and revealed its adsorption mechanism. Inorganic/organicnanocomposite combined both the advantages of rigidity, dimensional stability,thermostability of inorganic nano particles and toughness, workability, dielectric properties oforganic polymers. However, in the practical application of inorganic/organic nanocomposite,its performance would be weakened owing to the severely agglomerated inorganic nanoparticles.The starting point of this study was the value-raised utilization of lignin, which was a kindof biomass resources. A sulfonated lignin-based macromolecule polymer, SBAL, wasprepared by sulfomethylation, etherification and polycondensation reactions. A phosphatizedlignin-based macromolecule polymer, GPL, was prepared by phosphorylation reaction. Bothof them were using alkali lignin from the alkaline pulping spent liquor (BAL) as the mainmaterial. The structural characteristics and solution behaviors of SBAL and GPL wereinvestigated by means of FT-IR,1H NMR, dynamic light scattering, TEM, zeta potential andthermoanalysis. Moreover, the adsorption characteristics of SBAL and GPL on solid/liquidinterface at different pH values were determined using a quartz crystal microbalance withdissipation monitoring (QCM-D) and electrostatic layer-by-layer self-assembly, as well asUV-Vis spectroscopy and atomic force microscope (AFM). A newly kind of silica/ligninnanocomposite particle was prepared by combining the GPL (precipitant and dispersant),SBAL (auxiliary dispersant) and nano-slilica by means of acidulation precipitation at roomtemperature and atmosphere pressure. What’s more, the physico-chemical properties andstructural characteristics of silica/lignin nanocomposite particles were further investigatedthrough BET, SEM, TEM, zeta potential test, dispersion stability test, TG, FT-IR, XPS, XRD,static contact angle measurements, etc. and thus revealed its formation mechanism.The results indicated that with the increase of pH, the hydrophilic functional groups ofSBAL: sulfonic, carboxyl and phenolic hydroxyl groups were ionized gradually. The molecular configuration of SBAL changed from coil chain to extended chain and henceexpanded its three-dimensional space network. The carboxyl group was mainly inside theSBAL molecules, while the sulfonic and phenolic hydroxyl groups were mainly on itsmolecule surfaces. With the pH increased from3to12, the adsorption amount of SBAL ongold plate and quartz slide decreased at first and then increased, the lowest amount was at pH9. The adsorption configuration of SBAL changed from rigid to soft, tight to loose and thentight again, its adsorption conformations on gold plate and quartz slide withpoly(diallyldimethylammonium chloride)(PDAC) were mushroom-like structure,pancake-like structure and polymer brushes in the acidic, neutral and alkaline conditions,respectively. Cation-π interaction was the main driving force between SBAL and PDAC in theacidic and neutral conditions and the adsorption strength was weak. However, electrostaticinteraction played an important role between SBAL and PDAC in the alkaline condition andthe adsorption strength was strong.GPL was prepared by using alkali lignin from the alkaline pulping spent liquor of poplar,active monomer and phosphate as the main materials. The Mwof GPL was7,195Da and itsmolecules were spherical with diameter of about30~270nm and they would aggregate inaqueous solution. With the increase of pH, the hydrophilic functional groups of GPL:phosphate, carboxyl and phenolic hydroxyl groups were ionized gradually and the molecularconfiguration changed from coil chain to extended chain. The thermostability and thermaldecomposition temperature of GPL were both higher than BAL. The carboxyl group wasmainly inside the GPL molecules, while the phosphate and phenolic hydroxyl groups weremainly on its molecule surfaces. The ionizing degree of the phenolic hydroxyl groups of GPLwas low owing to its low group content. As for GPL, the adsorption characteristic was similarto SBAL in acid and neutral conditions, but in alkaline condition, it was quite different. Theadsorption amount of GPL on gold plate and quartz slide decreased as pH increased from3to12and the adsorption configuration changed from rigid to soft and tight to loose. Theadsorption conformations of GPL on gold plate and quartz slide with PDAC weremushroom-like structure in acidic, pancake-like structure in neutral and alkaline conditions,respectively. In the acidic condition, the aromatic ring of GPL would point toward the solidsurface with strong cation-π interaction and the hydrophilic groups of GPL would pointoutwards. However, in the neutral and alkaline conditions, the spread of molecular chainswould increase the distance between the aromatic ring and the cation, which would result inthe decrease of the cation-π interaction between GPL and PDAC and then increase thehydrophobicity of GPL. The favorable preparation process of silica/lignin nanocomposite particles was come outwith: SiO2-x+GPL+H2SO4, the pH titration endpoint was4and the ageing temperature andageing time were50℃and1h, respectively. According to the above process, two kinds ofsilica/lignin nanocomposite particles were prepared by means of infrared drying and spraydrying, respectively. The GPL was coating around the surface of nano-silica. Thethermostability of the nanocomposite particles was improved after the combination of GPLand nano-silica. Especially when above400℃, the weight loss ratio of the nanocompositeparticles was lower than GPL. When the nanocomposite particles were calcinated at200℃after spray drying, not only the dispersion of particles but also the thermostability were bothimproved. Moreover, the thermostability of the calcinated silica/lignin nanocompositeparticles with a weight loss ratio of only about15%was better than nano-silica before500℃.The silica/lignin nanocomposite particles were used as the modifier and blended with HDPE.The composite with the silica/lignin nanocomposite particles by means of infrared dryingshowed a better tensile strength than commercially nano-silica prepared by gas phase methodand precipitation method. As for the composite with the silica/lignin nanocomposite particlesby means of spray drying, although the tensile strength was a little smaller than thenano-silica prepared by gas phase method, its comprehensive mechanics performance wasalmost the same as the nano-silica prepared by precipitation method. However, it only costabout one third of the nano-silica prepared by precipitation method, which indicated a verygood cost advantage. |
PDF Full Text Request