【作者】 王丽平；

【导师】 黄柱成；

【作者基本信息】 中南大学 ， 矿业工程， 2012， 博士

【摘要】 随着近年工业的发展和人口的增加,水体污染治理面临严峻挑战。染料废水和重金属废水的高效治理成为目前研究的热点和难点。吸附法因其具有成本低,效率高,简单易操作并对有毒物质不敏感等优点,成为本研究首选治理技术。本研究首次提出并以Ni(NO3)2·6H2O为催化剂前驱体,C2H2为碳源,H2为还原气体,N2为载气,采用化学气相沉积法(CVD)在粘胶基活性炭纤维(ACFs)毡体中纤维表面催化生长碳纳米管(CNTs)制备了一种新型吸附材料-ACF/CNT复合材料。研究了制备条件的影响,分析研究了ACF/CNT复合材料的结构特征,查明了ACF/CNT复合材料制备机理并阐明了碳纳米管生长机制。结果表明：在活性炭纤维的表面生长了均匀而稠密的碳纳米管；在碳纳米管尖端发现碳、镍和氧三种元素；存在石墨态碳纳米管和面心立方结构的晶体镍；生长碳纳米管后材料的表面官能团发生了改变；ACF/CNT复合材料以微孔和中孔为主。复合材料中碳纳米管生长遵循气-液-固(VLS)顶部生长机制,而且发现碳纳米管优先生长在活性炭纤维的开孔边缘。针对罗丹明B、甲基橙、次甲基蓝和六价铬,通过改变C2H2裂解温度、裂解时间、催化剂前躯体浓度、C2H2流量和H2流量等制备条件,实现了ACF/CNT复合材料比表面积、表面基团和孔径分布等结构性能参数可控。研究ACF/CNT复合材料对水溶液中罗丹明B的吸附性能及机理,结果表明：当pH从2升高到3,吸附容量从16.36降低到16.29mg/g,而后吸附容量随着pH的增加而增加；对罗丹明B的吸附数据符合Langmuir吸附等温线和准二级动力学方程；颗粒间扩散不是唯一的控制步骤,吸附速率还受膜扩散控制。根据热力学计算结果,表明吸附过程为非自发的、吸热的物理吸附。研究ACF/CNT复合材料对水溶液中甲基橙的吸附性能及机理,结果表明：pH从2到3时,吸附剂吸附容量从96.88增加到114.81mg/g,而后增加幅度变慢；对甲基橙的吸附数据符合Langmuir等温吸附模型和准二级动力学方程；颗粒间扩散和膜扩散共同为吸附过程的控制步骤；热力学计算结果揭示吸附过程为自发的、放热的物理吸附过程。研究ACF/CNT复合材料对水溶液中次甲基蓝的吸附性能及机理,结果表明：吸附容量随着pH的增加而增加；对次甲基蓝的吸附数据符合Freundlich吸附等温线模型和准二级动力学方程；吸附过程被颗粒间扩散和膜扩散控制；热力学计算结果阐明吸附为自发的、吸热的物理吸附。研究ACF/CNT复合材料对水溶液中六价铬的吸附性能及机理,结果表明：当pH从2到3时,吸附容量从4.992下降为4.987mg/g;而后随着pH的增加,吸附容量急剧下降。吸附实验数据遵循Freundlich吸附等温线和准二级动力学模型,颗粒间扩散不是吸附速率唯一的控制步骤,还要考虑膜扩散的影响；经热力学计算,证明吸附过程为自发的、吸热的物理吸附。ACF/CNT复合材料吸附罗丹明B和次甲基蓝的吸附机理包括氢键作用力、静电引力、Π-Π键和微孔填充；吸附甲基橙的吸附机理包括氢键作用力、Π-Π键和微孔填充。ACF/CNT复合材料吸附六价铬的机理主要包含静电引力和微孔填充。更多还原

【Abstract】 Water pollution has become more and more serious with the development of industry and increase of population in recent years. The efficient treatment of dyes and heavy metals wastewater was proved to be one of the research hotspots and problems. The adsorption was selected to be preferred treatment technology in this study for its low cost, high efficiency, easy control and insensitive to toxic substance.In this paper, a new adsorption materials-ACF/CNT composites were firstly proposed and prepared with Ni(NO3)2·6H2O as catalyst precursor, C2H2as carbon source, H2as reduction gas and N2as carrier gas by growing carbon nanotubes(CNTs) on the surface of activated carbon fibers(ACFs) by chemical vapor deposition(CVD).The effects of preparation conditions and structure features were investigated for ascertaining the preparation mechanism of ACF/CNT composites and the growth mechanism of carbon nanotube. The results showed that CNTs were densely and well distributed on the surface of ACFs; C, Ni and O elements were found on the tip of CNTs; graphite CNTs and fcc nickel were found; the surface functional groups were changed after growing CNTs; micropores and mesopores dominated the ACF/CNT composites. The growth of CNTs followed VLS and top growth mechanism, and CNTs were found easy to grow on the pore sides.Aiming to rhodamine B, methyl orange, methylene blue and Cr(Ⅵ), controllability of performance and structure parameters including BET specific surface area, surface functional groups and pore size distribution was realized by adjusting pyrolysis temperature, pyrolysis time, catalyst precursor concentration, C2H2and H2flux.The adsorption abilities and mechanism of ACF/CNT composites for rhodamine B were showed that the adsorption capacity decreased from16.36to16.29mg/g with increasing pH from2to3, and then the adsorption capacity rised with increasing pH. The adsorption experimental data for rhodamine B were well fitted by Langmuir equation and pseudo-second-order kinetic model. The adsorption rate was not only controlled by intra-particle diffusion, but also by film diffusion. According to thermodynamic calculation, the adsorption process was a nonspontaneous and endothermic physisorption.The adsorption abilities and mechanism of ACF/CNT composites for methyl orange were investigated. The results showed that when pH rised from2to3, the adsorption capacity increased from96.88to114.81mg/g, then the increase rate droped. The adsorption experimental data of methyl orange were well described by Langmuir equation and pseudo-second-order kinetic model. The adsorption rate was controlled by intra-particle and film diffusion. The results from thermodynamic calculations suggested the the adsorption process was a spontaneous and exothermic physisorption.The adsorption abilities and adsorption mechanism of ACF/CNT composites for methylene blue were researched. The results declared that the adsorption capacity increased with increasing pH. The adsorption experimental data of ACF/CNT composites for methylene blue were well fitted by Freundlich equation and pseudo-second-order kinetic model. The adsorption rate was controlled by intra-particle diffusion and film diffusion. The results from thermodynamic calculations demonstrated that the adsorption process was a spontaneous and endothermic physisorption process.The adsorption abilities and adsorption mechanism of ACF/CNT composites for Cr(VI) were studied. The results indicated that when pH rised from2to3, the adsorption capacity decreased from4.992to4.987mg/g, then the decrease rate increased. The adsorption experimental data were well fitted by Freundlich equation. Furthermore, the kinetic data were well described by pseudo-second-order kinetic model. The adsorption rate was not only controlled by intra-particle diffusion, but also by film diffusion. The results from thermodynamic calculations indicated the adsorption process was a spontaneous and endothermic physisorption process.The adsorption mechanisms of rhodamine B and methylene blue are hydrogen bond, electrostatic attraction, n-n bond and micropore filling; the adsorption mechanisms of methyl orange are hydrogen bond, π-π bond and micropore filling. The adsorption mechanisms of Cr(VI) include electrostatic attraction and micropore filling.更多还原