Study On The Structure And Interface Properties Of Cellulose/magnesium Hydroxide

The interfacial chemistry is overarching research topic for nanocomposite materials,moreover,specification of local structure and clarification of interfacial interaction of biomacromolecular materials are of great significance in designing and synthesizing novel materials,advancing their performance in applications and understanding of interface chemistry.However,the composites feature rather complicated local structures and hydrogen bonds are often involved in the interface and the vicinity of active sites.These are extremely challenging,particularly for hydrogen-involved biomass composites due to limitations of experimental techniques like X-ray diffraction(XRD)and even neutron diffraction.In this regard,Density functional theory(DFT)and experiments were used to study the local structure and interfacial properties of cellulose/Mg(OH)₂ and cellobiose adsorbed Mg(OH)₂composites.First,biomass cellulose/magnesium hydroxide nanocomposite was synthesized via a hydrothermal approach and systematically examined by density functional theory(DFT)in terms of periodic boundary conditions.The composite shows layer-like morphology,where nano cellulose fibers are coupled with each other.Mg(OH)₂ pellets,around 50 nm in size,are well-dispersed,which either anchor onto cellulose surface or insert interlayers.The specific structure of the composite was recognized by DFT calculations,agreeing with our XRD,SEM and TEM observations.It is revealed that the interfacial interaction is hydrogen bonding in nature.Based on a composite model of three glucose chains and two-layer Mg(OH)₂ cluster particle,the adsorption energy averages-0.47?-0.26 e V per hydroxyl group of Mg(OH)₂ surface;only 0.09 e is transferred from the Mg(OH)₂ part to cellulose,indicative of very slight contribution to the interfacial coupling.Energetic calculations show that the incorporation of Mg(OH)₂reduces the mechanical strength of cellulose substrate,quantitatively approving previous experimental measurements.The composite features 2p(O)-character valence band maximum and conduction band minimum,coming from cellulose and Mg(OH)₂,respectively.The synergy of calculated and experimental results allows to propose the antibacterial mechanism of our composite.Next,density functional theory first-principle calculations associated with experimental study have synergistically examined two-dimensional(2D)magnesium hydroxide material with different layers and their adsorption toward cellobiose.Hydrogen bonds are found responsible for the interfacial coupling,which make it vital to cover the dispersion correction in the calculation.The average adsorption energy ranges from-0.29 to-0.35 e V,falling well within the range of reported hydrogen-bonding strength.On the basis of calculated structural/interfacial properties and experimental findings,the 2D Mg(OH)₂ in terms of three-layer model was unraveled to substitute toxic Cd²⁺ion and sorb radioactive UO₂²⁺that is coordinated by water and hydroxyl groups.These reactions are thermodynamically feasible.The ion-exchanging mechanism was proposed for cadmium removal and the outer-sphere adsorption one for uranium extraction.