生物碳对寒旱区石油污染黄土中多环芳烃吸附行为影响的研究

发布时间：2018-03-24 21:37

本文选题：黄土　切入点：石油污染物　出处：《兰州交通大学》2015年硕士论文

【摘要】：添加外源性物质(秸秆焚烧物和生物碳)可改良贫瘠黄土、提高肥力。研究外源性物质对寒旱区黄土吸附石油污染物的影响,对石油污染物在黄土中的归趋有重要意义。本文在研究寒旱区黄土对石油污染物的吸附特性的基础上,采用热重分析、元素分析、红外光谱分析、比表面积分析和电镜扫描表征小麦秸秆焚烧物(BC-ash)和生物碳(BC-200、BC-400、BC-600)的结构特征,分析不同的外源性物质对黄土吸附石油污染物的影响;初步探讨了柴油污染黄土对多环芳烃的吸附性能,并定量描述了柴油污染黄土上分配作用和表面作用对吸附总量的贡献。研究取得了以下成果:(1)热重、红外光谱分析结果显示小麦秸秆在热解温度升高到350℃时失重率最大,为33.73%,秸秆的热解过程发生化学键的断裂及脂肪性烷基链的消失;小麦秸秆焚烧物的产率、灰分分别为12%、64.78%,灰分较大;生物碳随着碳化温度的升高,其产率降低,灰分含量增大;随着热解温度升高,生物碳逐渐成为“富碳颗粒”,其极性降低,芳香性增大,疏水性增强;电镜扫描分析显示随着碳化温度升高,生物碳孔壁逐渐变薄,内部孔结构逐渐增大,甚至出现大量微孔。(2)寒旱区黄土对萘的吸附在10h内为快速吸附过程,24h达到吸附平衡;Pseudosecond-order模型能较好地描述萘在黄土上的动力学吸附过程,吸附过程由外部液膜扩散、表面吸附、颗粒内扩散控制;黄土对萘的吸附以分配作用为主,Henry和Freundlich模型均能很好地描述其吸附特性;黄土对萘的吸附是一个自发进行的吸热过程,随着温度的升高,萘的饱和吸附量增大,熵变是主要驱动力;比较两种黄土,兰州(LZ)对萘的饱和吸附量高于嘉峪关(JYG),黄土中粉粒含量也能显著影响吸附作用。(3)添加秸秆焚烧物黄土对萘的快速吸附过程在10h内完成,24h达到吸附平衡;初始浓度的增大增加了黄土及秸秆焚烧物颗粒表面吸附位点与萘的碰撞频率,导致平衡吸附量的增大;动力学吸附过程符合Pseudo-second-order模型,吸附的起始阶段萘分子迅速占据黄土颗粒及秸秆焚烧物吸附位点,之后吸附剂通过微孔扩散机制进入其内部;添加秸秆焚烧物黄土对萘的吸附是物理吸附,温度升高,有利于吸附的进行;添加秸秆焚烧物黄土对萘的吸附量略低于黄土本身,表明土壤有机质及其他组分与萘在吸附位点形成竞争吸附。(4)添加生物碳黄土对萘的吸附能力明显提高,快速吸附过程在10h内完成,吸附在20h达到平衡;动力学吸附过程符合Pseudo-second-order模型,吸附是多种机理控制的复杂体系多介质反应;添加生物碳使黄土吸附萘的非线性增强,生物碳多孔结构和芳香性影响吸附过程;生物碳热解温度越高,对黄土的非线性吸附过程影响越显著;酸洗过程能很大程度上去除灰分,但对生物碳无定型活性组分改变较显著,导致酸洗对不同温度条件下制备的生物碳吸附性能的影响有差异;(4)柴油污染黄土对萘的吸附在72h内达到平衡,柴油的存在显著延长了黄土对萘的动力学吸附过程;低浓度柴油污染黄土对萘的吸附量比高浓度柴油污染黄土大,其机理为高浓度条件下柴油类污染物与萘形成竞争吸附降低了萘在柴油污染黄土上的平衡吸附量;萘在柴油污染黄土上的吸附为非线性吸附过程,该过程既包含物理吸附也包含化学吸附;外源性物质的添加增大了表面吸附作用的贡献率,但柴油污染黄土上的表面吸附和分配作用都明显减弱;黄土中的柴油形成独立吸附相,对整个吸附过程有影响。
[Abstract]:The addition of exogenous substances (straw burning and biological carbon) can improve barren loess, improve soil fertility. Effects of exogenous substances on the adsorption of petroleum pollutants in cold and arid regions of the loess, the oil pollutants in the Loess fate has important significance. Based on the characteristics of adsorption of the dye on the stone cold and arid region of loess on the oil, using thermogravimetric analysis, elemental analysis, infrared spectroscopy, surface area analysis and SEM analysis of wheat straw burning material (BC-ash) and biological carbon (BC-200, BC-400, BC-600) structure, analysis of the impact of exogenous substances of different adsorption of petroleum pollutants in loess; to explore the adsorption performance of diesel contaminated loess for PAHs, and the quantitative description of the distribution of loess diesel pollution effect and surface effect on the adsorption of the total contribution. The research has achieved the following results: (1) thermogravimetry, infrared spectroscopy analysis showed that Wheat straw increased to 350 degrees in the pyrolysis temperature is 33.73%, the maximum weight loss rate, fracture and fatty alkyl chain of straw pyrolysis process of the chemical bond disappeared; wheat straw burning material yield, ash content were 12%, 64.78%, high ash; biological carbon with increasing carbonization temperature, the yield decreased. The ash content increases; with increasing pyrolysis temperature, the biological carbon gradually become a "carbon rich particles", which decreased the polarity of aromaticity increases, and increase the hydrophobicity; scanning electron microscopy analysis showed that with the carbonization temperature, the biological carbon hole wall thinning, the internal pore structure increases gradually, and even the emergence of a large number of micropores (2) adsorption. Cold and arid regions on the Loess of naphthalene in 10h rapid adsorption process, 24h adsorption equilibrium; Pseudosecond-order model can better describe the dynamic adsorption process of naphthalene in the Loess on the adsorption process by external film diffusion, surface adsorption, Particle diffusion control; adsorption of naphthalene on Loess distribution function, Henry and Freundlich model can well describe the adsorption properties; adsorption of naphthalene in the loess is a spontaneous endothermic process, with the increase of temperature, the saturated adsorption capacity of naphthalene increases, the entropy change is the main driving force; two loess, Lanzhou (LZ) on the adsorption capacity of naphthalene is higher than that of Jiayuguan (JYG), can significantly affect the adsorption of silt content in loess. (3) add straw burning process of loess rapid adsorption of naphthalene on 10h, 24h reached adsorption equilibrium; the concentration of collision frequency increases the Loess and the burning of straw particles and surface adsorption sites of naphthalene, increase the equilibrium adsorption; dynamic adsorption process with the Pseudo-second-order model, the initial stage of naphthalene molecular adsorption material quickly occupy adsorption sites of loess grains and straw burning, After adsorption by micropore diffusion mechanism is added into the interior; physical adsorption, adsorption of naphthalene on Loess straw burning temperature was beneficial to adsorption; adding straw burning adsorption capacity of naphthalene compounds in loess is slightly lower than that of loess itself, soil organic matter and its components and he formed in the naphthalene adsorption sites of competitive adsorption. (4) add biological carbon on the Loess naphthalene adsorption capacity increased significantly, the rapid adsorption process within 10h, the adsorption reached equilibrium in 20h; dynamic adsorption process with the Pseudo-second-order model, the adsorption is a complex system of multiple control mechanism of multi medium reaction; the Loess nonlinear adsorption of naphthalene enhanced biological carbon addition, biological adsorption process carbon porous structure and aromatic effect; biological carbon pyrolysis temperature is higher, the nonlinear adsorption process of the Loess influence is more significant; the pickling process can remove ash largely, but Amorphous active components change significantly on the biological carbon, cause effect of pickling on under different temperature conditions for bio carbon adsorption by the difference; (4) the adsorption of diesel contaminated loess on naphthalene reached balance within 72h, the presence of diesel significantly extended the power of the naphthalene adsorption process of low concentration loess science; the adsorption capacity of high concentration pollution of diesel diesel pollution loess for naphthalene, the mechanism for the high concentration of diesel pollutants and reduce the formation of naphthalene competitive adsorption equilibrium adsorption of naphthalene in diesel contaminated loess on the amount of adsorption of naphthalene on diesel pollution; loess on the nonlinear adsorption process, this process includes not only physical adsorption is also included chemical adsorption; exogenous substances added to increase the surface adsorption contribution rate, but the surface adsorption and distribution effect of diesel pollution on the loess are significantly reduced; the Loess formed independent diesel adsorption Phase, it has an effect on the whole adsorption process.

【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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