木材气凝胶过滤膜的制备及其处理含铜废水效果

Preparation of wood aerogel membrane and adsorption performance on Cu^(2+)in waste water

随着经济发展,重金属污染对生态环境和人类健康的危害日趋严重,制备工艺简单且可高效吸附重金属的新材料逐渐成为当前研究的热点。本研究以天然巴沙木为基材,在脱除木质素的基础上通过2,2,6,6-四甲基哌啶-1-氧基(TEMPO)氧化处理制备出了具有三维纳米网络结构的木材气凝胶过滤膜(TDWM),通过TEMPO氧化处理选择性地将纤维素中C 6位的羟基氧化成羧基,利用纤维素分子链间羧基的静电排斥作用将细胞壁分离成微纤丝纳米网络结构,提高木材比表面积的同时,利用细胞壁中产生的纳米孔隙结构,增加Cu^(2+)与细胞壁的接触面积,同时气凝胶过滤膜孔道中丰富的羧基为Cu^(2+)的吸附提供了大量活性位点。实验结果表明,TDWM对Cu^(2+)的最大静态吸附量达到115 mg/g,其吸附反应符合拟二阶动力学模型和Langmuir模型,说明气凝胶过滤膜中的羧基对Cu^(2+)通过化学络合而产生单层吸附;动态过滤结果显示,在1~5 mm的厚度范围内,TDWM的厚度与Cu^(2+)的去除效率呈正相关性,而且随着过滤层数的增加,Cu^(2+)的去除效率也会增大,厚度为5 mm的3层TDWM装置对Cu^(2+)的动态去除率可达98.28%。本研究制备的木材气凝胶过滤膜不仅工艺简单,而且具有优异的Cu^(2+)去除能力,对高效去除污水中的重金属离子显示出较大的应用潜力。

Heavy metal pollution has increasingly serious harm to the ecological environment and human health.Therefore,the development of new materials with simple preparation technology,low production cost,biodegradation and high efficiency adsorption of heavy metal ions has gradually become a research focus.In this study,wood aerogel filtration membrane(TDWM)with three-dimensional nano-network structure was prepared by the 2,2,6,6-tetramethylpiperidin-1-yloxy(TEMPO)oxidation treatment on the basis of using the natural balsa wood as the substrate,which selectively oxidized the hydroxyl group in the C_(6) position of cellulose to carboxyl group by the TEMPO oxidation treatment,and separated the cell walls into microfibrillar nano-network structure by using the electrostatic repulsion of carboxyl group between cellulose molecular chains.While increasing the specific surface area of wood,the contact area between Cu^(2+)and the cell wall was increased by using the nanopore structure generated in the cell walls,and the abundant carboxyl groups in the pore channels of the aerogel filter membrane provided a large number of active sites for the Cu^(2+)adsorption.The carboxyl content of the aerogel reached a maximum of 1.29 mmol/g when the oxidation time was 5 h.The chemical components of the wood aerogel membrane did not change significantly,while the crystallinity increased due to the TEMPO oxidation occurring firstly in the amorphous region of cellulose.Wood aerogel membranes with the TEMPO oxidation time of 5 h showed the largest specific surface area of 15 m^(2)/g,which was 11 times larger than that of the delignified wood(1.26 m^(2)/g).The static adsorption showed that the maximum adsorption capacity of TDWM for Cu^(2+)reached 115 mg/g,and the adsorption reaction was consistent with the pseudo-second-order kinetic model and Langmuir model,indicating that Cu^(2+)was adsorbed by the carboxyl group in the aerogel through the chemical complexation.Meanwhile,the dynamic adsorption studies showed that the thickness of TDWM was positively correlated with the removal efficiency of Cu^(2+)in the range of 1-5 mm.Moreover,the removal efficiency of Cu^(2+)increased with the increase of the number of filtration layers,and the dynamic removal efficiency of Cu^(2+)can reach 98.28% when the thickness of the three-layer TDWM device was 5 mm.The wood aerogel membrane prepared in this study is not only simple,biodegradable,low preparation cost,but also has excellent Cu^(2+)adsorption capacity,showing great application potential for efficient removal of heavy metal ions in sewage.