不同类型吸附剂对钒（V）吸附行为的研究

发布时间：2018-04-01 04:47

本文选题：土壤胶体　切入点：生物质炭　出处：《西北农林科技大学》2017年硕士论文

【摘要】：土壤重金属污染给粮食安全生产带来严重威胁,土壤中重金属污染物的形态转化及迁移累积引起广大学者的关注。环境中的钒随饮食、呼吸等方式被带入动物体内,对人类健康造成威胁。钒污染虽然不会立即威胁全球范围内的生态系统,但是随着钒的沉积和迁移,会逐渐破坏生态环境。深入研究钒在土壤环境中的迁移和转化机制,将非常有利于钒的污染治理与环境标准的制定,从而实现农产品更加安全的生产。本文以五价的钒为研究对象,采用陕西省典型的黄褐土、X土、风沙土、黄绵土、以及相应的土壤胶体和改性锯末生物质炭为吸附材料,通过吸附动力学及与等温试验,分析不同吸附材料对V(V)的吸附能力的差异性,结合比表面积(BET)、傅里叶红外光谱(FTIR)、X衍射分析(XRD)、电子扫描电镜(SEM)和原子力显微镜(AFM)等分析表征手段,探索不同吸附材料对V(V)的吸附机理。上述研究旨在揭示不同吸附剂对V(V)的固持能力的大小,为了解V(V)在土壤中的行为和生物质炭的环境生态修复提供科学依据。本研究取得了以下主要结论:(1)不同土壤对钒吸附能力的大小黄褐土、X土、风沙土和黄绵土由于物理化学性质(有机质含量、比表面积、粒径分布和矿物成分)的不同,对V(V)的吸附也存在较大差异。完成快速吸附V(V)的反应时间分别为60min、120min、120min和30min,动力学数据最为符合拟二级动力学模型。这表明土壤吸附钒是一个复杂的化学吸附与物理吸附共存的动态吸附过程。Freundlich模型能较好地拟合等温吸附数据,陕西土壤对V(V)的吸附为多分子层吸附,黄褐土、X土、风沙土和黄绵土对V(V)的最大吸附量分别为1147.4 mg·kg-1,854.4 mg·kg-1,748.6mg·kg-1,730.8 mg·kg-1。pH值为4到8时黄褐土、X土、风沙土和黄绵土吸附V(V)的最大吸附能力较稳定,同时吸附能力随着离子强度的增加而降低。(2)钒在不同土壤胶体上的吸附行为特征通过原子力显微镜(AFM)结果发现,与风沙土和X土胶体相比,黄绵土胶体粒径最大为181.30 nm。XRD结果分析显示天然土壤胶体中主要的矿物成分包括黑云母、高岭石、方解石和石英。土壤胶体对V(V)的吸附动力学和等温线分别能较好的被Pseudo-second-order和Freundlich模型拟合。Langmuir模型拟合结果表明X土和风沙土胶体对V(V)的最大吸附能力相差不大,黄绵土胶体对V(V)的吸附能力较弱,最大吸附量分别为285.7 mg g-1、238.1 mg g-1和41.5 mg g-1。吸附能力的差异与土壤胶体的粒径大小和有机质含量有直接关系,且化学吸附过程主要作用于羧基和羟基官能团。在pH影响试验中,X土胶体在溶液初始pH值介于5.0--9.0之间吸附量最佳,风沙土和黄绵土胶体的最佳为6.0--8.0。随离子强度的增加,土壤胶体对V(V)的吸附能力相应减小。(3)改性锯末生物质炭对钒吸附特征随着pH值的升高,改性锯末生物质对钒的吸附量先增加后减小,其中pH在7左右时,吸附量达到最大,为15.766 mg.g-1。改性生物质炭在前1小时内迅速完成对钒的吸附过程,在24小时左右达到吸附平衡,吸附动力学拟合结果符合拟二级动力学方程。原始生物质炭对钒的最大吸附量为1.9905 mg.g-1,Fe改性生物质炭对钒的最大吸附量为17.231 mg.g-1,改性炭对钒的吸附量是原始炭吸附量的8.66倍。锯末生物质炭经过Fe负载改性,改变生物质炭的元素组成,降低了生物质炭的孔隙度,可显著提高生物质炭对钒的吸附性能。改性生物质炭对钒良好的吸附性能主要归功于其表面的正电荷对阴离子形态钒的吸附作用。
[Abstract]:The soil heavy metal pollution poses a serious threat to food safety, aroused the attention of scholars form transformation and migration of heavy metal pollutants in the soil. The accumulation of vanadium in environment with diet, breathing etc. were brought into the animal body, a threat to human health. Although vanadium pollution does not immediately threaten the ecological system in the world, but with the the migration and deposition of vanadium, will gradually destroy the ecological environment. Study on the migration and transformation mechanism of vanadium in soil environment will be very thorough, making pollution control and environmental standards for vanadium, so as to realize the agricultural products more secure production. This paper takes the pentavalent vanadium as the research object, the typical yellow soil, Shaanxi X soil, sandy soil, loessial soil, and the soil colloid and the corresponding modified sawdust charcoal adsorption material, the adsorption kinetics and isothermal adsorption test and analysis of different. The material of V (V) the difference of the adsorption capacity, combined with the specific surface area (BET), Fourier transform infrared spectroscopy (FTIR), X diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) and other characterization techniques, explore the different adsorption material for the adsorption of V (V) the study aims to reveal the different mechanism of adsorption of V (V) of the holding capacity of V (V), in order to provide scientific basis for the ecological environment restoration in the behavior of the soil and the biomass carbon. This research has made the following main conclusions: (1) different soil adsorption capacity of vanadium in yellow cinnamon soil. X soil, sandy soil and loess soil due to physical and chemical properties (organic matter content, specific surface area, particle size distribution and mineral composition) of different V (V) adsorption are also quite different. The rapid adsorption of V (V) reaction time were 60min, 120min, 120min and 30min, kinetics the quasi two level data in line with the This shows that the soil mechanics model. Adsorption of vanadium is the dynamic adsorption process.Freundlich model is a complex physical adsorption and chemical adsorption coexist can better fit the adsorption data, Shaanxi soil on V (V) adsorption for multi molecular layer adsorption, yellow cinnamon soil, X soil, sandy soil and loess soil on V (V) the maximum adsorption capacity was 1147.4 Mg - kg-1854.4 Mg - kg-1748.6mg - kg-1730.8 Mg - kg-1.pH value of 4 to 8 yellow cinnamon soil, X soil, sandy soil and loess soil adsorption of V (V) and the maximum adsorption capacity is relatively stable, at the same time the adsorption capacity decreased with increasing ionic strength and adsorption behavior (2). Vanadium in different soil colloid by atomic force microscopy (AFM) results showed that, compared with sandy soil and X soil colloid, loessial soil colloid particle size up to 181.30 nm.XRD results showed that the main mineral component comprises biotite natural soil colloid, kaolinite, Calcite and quartz. Soil colloids on V (V) adsorption kinetics and isotherms were better by Pseudo-second-order and Freundlich model.Langmuir model fitting results show that the X soil and sandy soil colloids on V (V) and the maximum adsorption capacity difference, loessial soil colloids on V (V) adsorption capacity is weak, the maximum adsorption were there is a direct relationship between Mg g-1238.1 mg g-1 between 285.7 and 41.5 mg g-1. adsorption capacity and soil colloid particle size and organic matter content, and the main role in the process of chemical adsorption of carboxyl and hydroxyl functional groups. In the pH impact test, X value of soil colloid adsorption between 5.0--9.0 optimal solution at the initial pH wind, sand and loess soil colloid best to increase the 6.0--8.0. with ionic strength, soil colloids on V (V) adsorption capacity decreased. (3) modified sawdust charcoal on the adsorption characteristics of vanadium with pH value The increase of modified sawdust adsorption capacity of vanadium increased first and then decreased, the pH was 7, the adsorption capacity reached the maximum, complete the adsorption process of vanadium rapidly in the first 1 hours of 15.766 mg.g-1. modified biomass carbon, adsorption equilibrium in about 24 hours, the adsorption dynamic fitting results with quasi mechanics the two order kinetics equation. The maximum adsorption capacity of vanadium raw biomass carbon is 1.9905 mg.g-1, Fe modified biomass carbon maximum adsorption capacity of vanadium is 17.231 mg.g-1, the adsorption capacity of vanadium modified activated carbon is 8.66 times higher than the original carbon adsorption. The sawdust carbon after Fe load modification, change of biomass carbon elemental composition, reduced the biomass carbon porosity, can significantly improve the adsorption performance of biochar on adsorption of vanadium. The positive charge modified biomass carbon on adsorption performance of vanadium is mainly due to its good surface morphology of vanadium by anion.

【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X53;O647.33

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