天然有机物对改性天然菱铁矿去除地下水中砷的影响研究

发布时间：2018-06-16 07:18

本文选题：改性天然菱铁矿 + 有机物　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：由于具有强烈的毒性以及致癌性,饮用水砷严重危害到人们的身体健康。作为主要饮用水源,高砷地下水已经全世界共同关注的问题。迄今已发现国内40多个县(旗、市),都有高砷地下水的存在,其砷含量超过我国现行的饮用水卫生标准,导致地方性砷中毒时有发生。因此,地下水的砷污染已经受到政府以及公众的高度重视。天然有机物(NOM)广泛存在于高砷地下水环境中,有机物分子在各个方向上带有很多活性基团,具有较强的配合能力和吸附能力,能与环境中的金属离子、氧化物、氢氧化物以及矿化物等发生相互作用。因此,机物的存在严重影响(类)金属在地下水中的去除及迁移。本文选取改性天然菱铁矿(MGNS)作为吸附剂,研究天然有机物腐殖酸(HA)和富里酸(FA)对MGNS去除水中砷(As)效果的影响。通过一系列批实验,研究在(NOM-MGNS)-As体系和(NOM-As)-MGNS体系中,不同浓度以及不同类型的有机物存在时,MGNS的除As效果。针对批实验结果,将数据进行Lagergren动力学以及等温吸附模型拟合,并利用HPSEC-ICP-MS、FTIR以及EXAFS等分析手段,探讨HA/FA对MGNS除As影响的机理。实验结果表明,有机物浓度较低时(0~20 mg/L,以TOC计),NOM对改性天然菱铁矿去除As(III)几乎没有影响,而对As(V)有轻微的抑制作用,其吸附过程都比较符合Lagergren假二级动力学方程以及Langmuir等温吸附模式。随着有机物浓度(40 mg/L,以TOC计)的增大,NOM对改性天然菱铁矿去除As(III)仍然影响不大,但对As(V)的抑制作用随着有机物浓度的增大明显加强。在吸附过程中,并未发生As(III)、As(V)形态转变。与HA相比,FA对改性天然菱铁矿除砷的影响更大一些;与As(III)结果相比,有机物对改性天然菱铁矿去除As(V)的抑制作用更强,而对As(III)没有明显影响。有机物对改性天然菱铁矿去除水中砷的影响机理为:有机物与Fe的氧化物或氢氧化物络合反应,生成Fe(II)-NOM和Fe(III)-NOM的大分子物质,占用吸附剂表面的有效吸附位点,并使得附剂表面带负电荷,对As(III)/As(V)形成静电排斥力,从而导致改性天然菱铁矿的除砷效率降低。与As(V)相比,As(III)与吸附剂发生氧化还原、吸附等一系列反应,而As(V)主要为吸附反应,所以有机物与As(V)的吸附竞争更强烈一些。
[Abstract]:Because of its strong toxicity and carcinogenicity, arsenic in drinking water is harmful to people's health. As the main drinking water source, high arsenic groundwater has been a common concern all over the world. Up to now, it has been found that there are high arsenic groundwater in more than 40 counties (banners and cities) in China, whose arsenic content exceeds the current sanitary standard of drinking water in our country, resulting in endemic arsenic poisoning occurring from time to time. Therefore, arsenic pollution of groundwater has been highly valued by the government and the public. Natural organic compounds (NOM) exist widely in high arsenic groundwater environment. Organic molecules have many active groups in all directions, have strong coordination ability and adsorption ability, and can interact with metal ions and oxides in the environment. Hydroxides and mineralizations interact. Therefore, the presence of mechanical objects seriously affects the removal and migration of metals in groundwater. In this paper, modified natural siderite (MGNS) was selected as adsorbent to study the effect of humic acid (HA) and fulvic acid (FAA) on the removal of arsenic and aspartate from water by MGNS. A series of batch experiments were carried out to study the effect of MGNS on the removal of as in the system of NOM-MGNS- as and NOM-As-MGNS with different concentrations and different types of organic compounds. The Lagergren kinetic and isothermal adsorption models were used to fit the results of batch experiments. The mechanism of the effect of HA / FA on the removal of as from MGNS was discussed by means of HPSEC-ICP-MSM FTIR and EXAFS. The experimental results show that when the concentration of organic matter is low, 20 mg / L, NOM has little effect on the removal of As-III by modified natural siderite, but has a slight inhibitory effect on As-V. The adsorption process accords with Lagergren pseudo-second-order kinetic equation and Langmuir isothermal adsorption model. With the increase of organic concentration (40 mg / L), NOM still has little effect on the removal of As-III from modified natural siderite, but the inhibition of As-V) is obviously strengthened with the increase of organic concentration. During the process of adsorption, there was no change in the form of As1 / II-AV). Compared with HA, FA has a greater effect on arsenic removal from modified natural siderite, and organics have stronger inhibitory effect on removal of As-V than modified natural siderite, but have no obvious effect on As-III. The effect mechanism of organic compounds on removal of arsenic in water by modified natural siderite is as follows: organic compounds react with oxides or hydroxides of Fe to form macromolecular substances of FeOIII-NOM and FeII-NOM, which occupy the effective adsorption sites on the surface of adsorbent. The negative charge on the surface of the adsorbent formed electrostatic repulsive force on As-III- / As-V, which resulted in the reduction of arsenic removal efficiency of modified natural siderite. A series of reactions, such as redox, adsorption and so on, take place with the adsorbent, and the adsorption of the organic compounds is mainly adsorption, so the adsorption competition between organic compounds and asmonium V) is stronger.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X523

【参考文献】