Construction And Adsorption Mechanism Of Functional Woody Aerogel

Wood resource is one of the most abundant renewable resources on the earth.Woody aerogels prepared from woody materials are one of the important directions for the highly efficient utilization of wood resources.At present,Woody aerogels have emerged in the field of water treatment.However,low adsorption capacity and poor recyclability are key factors for limiting the large-scale practical application of woody aerogels in the field of water treatment.In this study,woody materials were used as precursors to construct functional woody aerogels through reasonable structural control and interface design.The woody aerogels exhibit excellent adsorption capacity and recyclability for removal of heavy metal ions.The formation mechanisms of woody aerogel were studied.The adsorption mechanism of the surface functional groups on heavy metal ions were analyzed.The structure activity relationship among“structure control-performance impacts-function applications”in woody aerogels was explained.The main research contents and results are as follows:（1）The MOF-808-EDTA@TCNF aerogels with hierarchical porous structure were fabricated from2,2,6,6-tetramethylpiperidin-1-oxyl-oxidized cellulose nanofibrils（TCNF）and metal organic framework（MOF-808-EDTA）through in situ deposition.The density and porosity of the MOF-808-EDTA@TCNF aerogel were 0.005 g cm^-3and 99.82%,respectively.These aerogels exhibited outstanding uptake capacity of 300.3 mg g^-1,and still maintained good adsorption efficiency for Cu²⁺after five continuous adsorption-desorption cycles.The adsorption process conformed to the Langmuir models,suggesting that the monolayer chemisorption was a rate control step.The adsorption mechanism of the aerogels for Cu²⁺was hydrogen bonding,electrostatic attraction,chemical coordination and chelation.（2）The high stable TCNF/TMPTAP/PEI aerogels with 3D perforated structure were successfully prepared through the reactivity of trimethylolpropane tris-（2-methyl-1-aziridine）propionate（TMPTAP）crosslinker towards carboxyl organics.The density and porosity of the TCNF/TMPTAP/PEI aerogel were 0.011 g cm^-3and 99.28%,respectively.The aerogels exhibited maximum adsorption capacity of485.44 mg g^-1,and still maintained high adsorption efficiency of 90%for Cu2+after five adsorption-desorption cycles.The adsorption data conformed to the Langmuir models,indicating that the monolayer chemisorption was a rate control step.The adsorption mechanism of the aerogels for Cu²⁺was attributed to the hydrogen bonding and chelation.（3）The highly compressible TCNF/TMPTAP/GO aerogels with anisotropic porous structure were successfully prepared from TCNF,TMPTAP and graphene oxide（GO）through directional freeze-drying technology.The density and porosity of the TCNF/TMPTAP/GO aerogel were 0.007 g cm^-3and99.548%,respectively.The aerogels showed the maximum adsorption capacity for Pb²⁺,Cu²⁺,Zn²⁺,Cd²⁺,and Mn²⁺of 571 mg g^-1,462 mg g^-1,361 mg g^-1,263 mg g^-1,and 208 mg g^-1,respectively,and still maintained high adsorption efficiency of 90%for Pb²⁺after five adsorption-desorption cycles.The adsorption data conformed to the Langmuir model,suggesting that the monolayer chemisorption was a rate control step.The adsorption mechanism of the aerogels for Cu²⁺was attributed to the hydrogen bonding and chelation.（4）The wood composite aerogels with high mechanical strength and low cost were successfully prepared using wood natural anisotropic hierarchical porous structure template crosslinked with semi-interpenetrating polymer network.The density and porosity of the wood composite aerogel were0.12 g cm^-3and 92%,respectively.The aerogels exhibited high yield strength of 566 k Pa and Young’s modulus of 56.335 MPa.The maximum adsorption capacity for Cu²⁺was 296 mg g^-1,and the removal efficiency of Cu²⁺only decreased by 13.5%after five adsorption-desorption cycles.The adsorption process conformed to the Langmuir model,indicating that the monolayer chemisorption was a rate control step.The adsorption mechanism of the aerogels for Cu²⁺was attributed to the hydrogen bonding,metal coordination,and chelation.