【作者】 高伟；

【导师】 赵广杰；

【作者基本信息】 北京林业大学 ， 木材科学与技术， 2018， 博士

【摘要】 以木质活性碳纤维(WACF)氧化改性和结构演变规律为目的,研究了 WACF的制备并使用硝酸和硝酸铈铵(CAN)氧化改性,探究了二者协同改性规律,主要结论如下:(1)得到了 WACF的制备工艺和基本性能。改性前WACF氧原子浓度为12.13%,石墨无序碳材料,V型水蒸汽吸附等温线。孔容为50.16 mmol/g,水吸附比表面积为65.40 m2/g,对HgC12的汞离子吸附符合准二级动力学方程。(2)硝酸氧化度改性可以增加氧原子浓度比例。酚基和醇基官能团含量随硝酸浓度增加而增多,随着时间的延长而减少;羟基官能团含量随温度升高和时间的延长而显著增多;羧基官能团含量随着硝酸浓度的提高而增多。WACF表面的石墨化程度随硝酸浓度提高而提高,芯部石墨化程度整体提高但不受浓度梯度的影响。硝酸改性后WACF的水吸附孔容降低,水吸附比表面积显著增加,平均增幅164%,最大增幅为259%。(3)CAN改性后的WACF含氧官能团增加,氧原子浓度上升,羟基官能团向高价态转变。拉曼检测结果均具有D峰和G峰。CAN氧化改性对WACF表面石墨化程度无影响,但显著提高了 WACF截面石墨化程度。WACF改性后孔的容积降低,水吸附比表面积显著提升。CAN改性可以提高汞吸附能力,改性过度时反而降低。(4)协同改性后WACF的氧/碳比值平均值为0.160。酚基和醇基含量提高。羧酯含量与氧化强度总体呈反比。羧酯基的含量均低于未改性样品。样品表面石墨化程度略有降低,样品芯部的石墨化程度略有提高。协同改性后孔体积降低。水吸附的比表面积显著提升。汞吸附能力与水吸附比表面积和氧原子浓度呈线性关系。硝酸可以增加官能团含量,对结构影响较小。(5)硝酸氧化改性,增加了 WACF表面官能团,微调孔结构,降低孔容,侧重于表面改性。CAN氧化改性,提高石墨化结构,腐蚀孔结构降低孔容量,双向调整孔容,微调官能团含量,侧重于结构改性。二者协同可定向微调孔径和增加含氧官能团,对靶向吸附等具有指导意义。更多还原

【Abstract】 In order to understand the oxidation modification of surface and structural of wood active carbon fiber(WACF),WACF was prepared and modified with nitric acid and ammonium nitrate(CAN)to explore their synergistic modification regular pattern.The following conclusions were described as follows(1)The preparation process and basic properties of WACF were obtained Before modification,the concentration of oxygen atoms of WACF was 12.13%,the graphite was disordered carbon material and the vapor adsorption isotherm belonged to the V type.The pore volume was 50.16 nunoUg and the water adsorption specific surface area was 65.40 m2/g,thus the adsorption of HgC12 was in line with the Quasi-second-order kinetic equation.(2)The enhancement of nitric acid oxidation increased the proportion of oxygen atoms.The content of phenol and alcohol functional groups increased with the increment of nitric acid concentration,and decreased with time.The content of hydroxyl group increased signi ficantly with the increase of temperature,time and nitric acid concentration.The graphitization degree on the surface of WACF rose with the increase of nitric acid concentration,and the graphitization degree in the core increased as a whole,but it was not affected by the concentration gradient.The water adsorption pore volume of WACF decreased after nitric acid modification The specific surface area of water adsorption rose remarkably with an average increase of 164%and a maximum increase of 259%(3)The oxygen-containing functional groups increased after CAN modification,the oxygen atom concentration rose,and the hydroxyl functional groups changed to high valence state.Both the D peak and G peak appeared in the Raman spectra.CAN oxidation modification had no effect on the graphitization of WACF surface,however,it significantly increased the graphitization degree of WACF cross section.The pore volume reduced after WACF modification,but specific surface area of the water adsorption increased obviously.CAN modification improved the mercury adsorption capacity,but the mercury adsorption capacity was reduced when it was modified excessively.(4)The average value of oxygen/carbon ratio of synchronous modified WACF was 0.160.The content of phenolic groups and alcohol groups increase.It presented an inverse correlation between the content of carboxyeste and the intensity of oxidation.The content of carboxyl ester group was lower than that of umnodified sample.The degree of graphitization on the sample surface reduced slightly,and the degree of graphitization of the sample core increased subtly.After synergistic modification,the pore volume decreased.The specific surface area of water adsoiption increased significantly.The adsorption capacity of mercury and the specific surface area of water adsorption were linearly related to the concentration of oxygen atoms.Nitric acid can increase the content of functional groups,and has little effect on the structure.(5)Nitric acid oxidation modification focused on surface modification by increasing the functional groups of WACF surface,fine-tuning the pore structure and reducing pore volume.While the Oxidation modification of ceric ammonium nitrate focused on structural modification by improving the structure of graphitization,reducing the pore volume because of the corroded hole structure,adjusting the pore volume in both directions and fine-tuning the functional group content.The cooperation of the two can be used to fine-adjust the pore size and increase the oxygen-containing functional groups,which has guiding significance for targeted adsorption.更多还原