Preparation Of Amino-functionalized Wood Aerogel And Its Adsorption Performance For Cu²⁺

Heavy metal ions discharged from industrial wastewater have caused severe environmental and ecological crisis due to their high toxicity and non-degradability.Therefore,removing heavy metal ions from wastewater has become a fast-rising issue in both research community and industry.Recently,three-dimensional（3D）porous adsorbents used for heavy metal remediation have received significant research attention due to their advantages of high efficiency and simple operation.As a renewable,sustainable,and eco-friendly natural material,wood has abundant porous structure（e.g.,tracheids,vessels,and pits）and functional groups（e.g.,hydroxyl and carboxyl groups）,thus holding great potential for heavy metal ion adsorption.In this study,a highly porous 3D amino-functionalized wood aerogel was developed as an efficient bio-adsorbent for Cu（Ⅱ）removal.The main results are as follows:（1）Highly porous wood aerogel was prepared directly from natural balsa wood by selectively removing lignin and hemicelluloses using the aqueous solutions of Na Cl O₂/CH₃COOH and Na OH,respectively.The delignification process was validated by FT-IR spectra,where the characteristic peaks of lignin(1462 cm^-1、1505 cm^-1 and 1593 cm^-1)gradually disappeared with increasing in treatment time.Lignin was completely removed after12 h treatment.After further treatment with NaOH,the original honeycomb-like structure evolved into a lamellar structure with a low density of～68.0 mg/cm³,high porosity of～95.5%,and a high BET surface area of～15.4 m²/g.（2）The cellulose skeleton of the wood aerogel was oxidized to introduce carboxyl groups using TEMPO/Na Cl O/Na Br system,and polyethylenimine（PEI）was then grafted onto the oxidized cellulose skeleton to introduce amino groups.After functional treatment,the PEI was successfully grafted onto the cellulose skeleton of the wood aerogel.The color of the sample changed from white to yellow,whereas the lamellar microstructure still maintained with a low density of～77.2 mg/cm³ and porosity of～94.9%.（3）The amino-functionalized wood aerogel exhibited a maximum Cu（Ⅱ）adsorption capacity of 59.8 mg g^-1,which was significantly higher than those of the TEMPO-oxidized wood aerogel and natural balsa wood.The initial p H of 5.0 could be regarded as the optimal p H for Cu（Ⅱ）adsorption.The adsorption process can be well described by the pseudo-second-order and Langmuir isotherm models.The results indicate that the Cu（Ⅱ）adsorption by the PEI-Wood aerogel was dominated by a monolayer chemisorption process.