Preparation Of Wood Aerogel-based Composites And Their Microwave Absorption And Heavy Metal Ion Adsorption Properties

The electromagnetic pollution caused by the large-scale use of electronic equipment seriously threatens biosystem,communication safety and electromagnetic compatibility.At the same time,due to the rapid development of industries at home and abroad,a large number of biologically toxic,carcinogenic compounds and metal ions have been continuously released into the water environment.Radioactive heavy metal ions can destroy the protein structure of organisms and cause functional mutations,endangering the security of human and ecology.Natural renewable polyhydroxy cellulose has good prospects in water treatment due to its inherent light weight,high strength and rigidity,hydrophilicity,polyhydroxyl and biodegradability.In this study,wood was used as initial raw materials,and three-dimensional wood cellulose aerogels were directly prepared by chemical treatment of the"top-down"method.Then,using it as a substrate,several light-weight,multi-layer wood-based microwave absorbers and heavy metal ion traps were constructed using in-situ anchoring or hydrothermal methods.The results show that the polyhydroxy wood cellulose aerogel converted from wood not only acts as a structural carrier,but also can effectively promote the multiple absorption of microwaves or heavy metal ions between the wood aerogel layers.The wood-based microwave absorber and heavy metal ion trap prepared by this research successfully realized the high-efficiency absorption of microwaves and the safe and efficient treatment of heavy metal ions,opening up a new way of thinking and way for the efficient use of wood-based fiber resources.The high-value development and utilization of materials has laid a good scientific reserve and technical guidance,providing new research ideas and scientific methods for the further development and utilization of wood-based materials.The main findings are as follows:(1)A natural wood was used to prepare wood cellulose aerogel,and magnetic Fe₃O₄/ZIF-67rhombic dodecahedrons were anchored in situ to construct a low-density graded porous Fe3O4/ZIF-67 modified wood aerogel(Fe₃O₄/ZIF-67@WA).Due to the advantages of both aerogel multilayer and magnetic Fe₃O₄/ZIF-67 functional particles,microwaves can be reflected and absorbed by Fe₃O₄/ZIF-67 functional particles between layers after entering the wood composite aerogel.After repeated absorption and loss,microwaves are effectively absorbed.Therefore,Fe₃O₄/ZIF-67@WA exhibits excellent microwave absorption performance,with a maximum reflection loss(RL)of-23.4 d B.In addition,the wood composite aerogel shows a wide absorption band of 4.5 GHz.The prepared green magnetic Fe₃O₄/ZIF-67@WA will become a lightweight microwave absorbing material and be used in many occasions.(2)Exploring novel water purifier to efficiently remove heavy metal ions from the wastewater for clean water generations is of vital importance.Inspired by the hierarchical structure of natural wood and the chelation of amino group,a high-efficiency water purifier with ethylenediamine functionalized MIL-101(Cr)octahedrons anchored on the layer of wood aerogel(MIL-101(Cr)-ED/WA)was constructed.Benefiting from the two-pronged approach with the hierarchical structure of the wood aerogel frame utilized for multistage filtration and the-NH₂that capable of chelation with metal ions,the fabricated MIL-101(Cr)-ED/WA exhibits excellent water purification performances,and its adsorption capacity of toxic Pb²⁺ions could reach up to 6.46 mmol g^-1.Furthermore,it demonstrates superior recyclability without secondary pollution and is also suitable for simultaneous treatment of multiple metal species.In general,this work pioneers the utilization of wood-based structural engineering materials in the treatment of heavy metal wastewater.(3)Exploring an efficient,stable and economical adsorbent material for the purification of toxic heavy metal ions wastewater is of great significance.However,as a typical heavy metal ions adsorbent,titanate materials still face huge improvement in material synthesis,adsorption efficiency and the recyclability.Herein,wood cellulose aerogel is broken into cellulose solution by mechanical processing,and Ti₃C₂T_x MXene-derived hydroxyl-rich titanate/cellulose membrane adsorbent is prepared to effectively remove toxic heavy metal ions.Owing to the similar stratified structure,the conversion process from Ti₃C₂T_x MXene to the titanate is energy-saving and easy to achieve.In addition,the inherited hydroxy-rich structure is beneficial to improve the adsorption efficiency of the derived titanate.Furthermore,the introduction of cellulose to fabricate a titanate/cellulose membrane could greatly alleviate the problem of difficult recycling of powder adsorbent.Thus,compared to the traditional titanate materials,the constructed Ti₃C₂T_x-derived hydroxy-rich titanate/cellulose membrane adsorbent(M-NTO/CM)exhibits high Cu²⁺adsorption capacity of 2.63mmol/g and can reach the adsorption equilibrium in only 5 min.Better yet,there has also been a significant improvement in acid resistance and recyclability of the novel M-NTO/CM relative to traditional titanate.In short,M-NTO/CM derived from Ti₃C₂T_x MXene can be used as an advanced membrane for convenient and efficient purification of heavy metal ions from the wastewater.