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题名: 纳米Fe3O4控磷效能的调控及其机理研究
作者: 丁程程
学位类别: 硕士
答辩日期: 2010
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 潘纲
关键词: 纳米Fe3O4 ; 可溶性淀粉 ; 粒径 ; 除磷
中文摘要:       本文利用氧化沉淀法,通过调节制备过程中可溶性淀粉的浓度,实现了纳米Fe3O4的粒径调控,并考察了不同粒径下Fe3O4的控磷效能,由粒径调控进一步实现了控磷效能的调控,为在土壤中实现最大限度地控磷提供了依据。本文得到以下主要结果: 通过对所合成不同淀粉浓度包覆Fe3O4进行表征,发现所合成Fe3O4均为单相的反尖晶石结构,淀粉包覆没有改变其晶体结构。淀粉与Fe3O4之间通过C-O结合,等电点向低pH方向移动。不同淀粉浓度包覆纳米Fe3O4均具有较高的饱和磁化强度(≥26.49 emu/g),0.5%淀粉包覆Fe3O4具有超顺磁性。 可溶性淀粉能够控制Fe3O4晶核的生长过程,从而能较好地调控纳米Fe3O4的晶粒粒径,粒径由无淀粉包覆时的~60 nm减小为0.5%淀粉包覆时的~10 nm。由于淀粉大分子之间的架桥作用、静电排斥力以及空间位阻的共同作用,随着淀粉添加浓度的升高,Fe3O4的水力粒径呈现先减小后在增大再减小的趋势,0.1%淀粉包覆Fe3O4的水力粒径最大,为~5000 nm,与无淀粉包覆Fe3O4的水力粒径相接近;0.5%淀粉包覆Fe3O4的水力粒径最小,小于100 nm。 淀粉包覆纳米Fe3O4的除磷效能好于无淀粉包覆Fe3O4,除磷效能与水力粒径没有负相关关系,随着淀粉添加浓度的升高,呈现先增加后略微减小的趋势。淀粉包覆能够将纳米Fe3O4表面钝化,将部分有效吸附位覆盖。磷在淀粉包覆Fe3O4表面的吸附等温线符合Freundlich等温线方程。随着淀粉添加浓度的升高,磷在纳米Fe3O4表面的吸附趋于可逆,吸附构型单角比例逐渐增多。准二级动力学方程能够较好的描述磷在不同淀粉浓度包覆Fe3O4表面吸附的动力学过程,吸附由表面反应过程控制,并且随着淀粉添加浓度的升高,反应速率常数减小。 水溶液中,当淀粉包覆层被降解后,淀粉包覆Fe3O4因发生团聚使得吸附能力有所下降;土壤中,淀粉包覆Fe3O4表面包覆层的降解使得有效吸附位被释放,吸附能力进一步提高。
英文摘要:       In this study, nano-scale magnetite was synthesized in the presence of soluble starch by a modified oxidation deposition method. The size of magnetite nanoparticles was successfully controlled via varying the concentration of soluble starch in the medium. The phosphate adsorption capabilities and stability of magnetite with different particle size were studied. Physical characterization showed that the crystal structure of magnetite coated with different concentration of starch was the inverse spinel structure, and the starch surface coating did not destruct the crystal structure of magnetite. There was a chemical complex formed between starch and magnetite. Compared with bare Fe3O4, the isoelectric point of magnetite coated with starch shifted to lower pH. All as-prepared magnetite had a relatively high saturation magnetiztion (≥26.49 emu/g), and Fe3O4 coated with 0.5% starch was super paramagnetic. Varying the concentration of soluble starch was easy to control the size of magnetite nanoparticles. With the increase of soluble starch concentration from 0% to 0.5% (w/v %), the size of magnetite nanoparticles decreased from ~60 nm to ~10 nm. The stability of Fe3O4 had no positive correlation with starch concentration, due to the bridging action, electrostatic repulsion and steric hindrance between nanoparticles. Fe3O4 coated with 0.1% starch obtained the lowest stability, while Fe3O4 coated with 0.5% starch held the highest stability. Compared with bare Fe3O4, all Fe3O4 coated with starch obtained higher adsorption capabilities. There was no negative correlation between the adsorption capability of Fe3O4 and their particle size. Surface starch coating would occupy the active sorption sites of magnetite nanoparticles. Freundlich equation was applicable for phosphate adsorption isotherms of magnetite. With the increase of starch concentration, the adsorption of phosphate onto magnetite became more reversible, and the portion of monodentate increased. The adsorption kinetics could be best described by pseudo second-order equation, which indicated that adsorption was controlled by surface reaction process, and the adsorption rate constant decreased with increasing starch concentration. In aqueous solution, when surface coating was degraded, the adsorption capability of Fe3O4 coated starch decreased due to the aggregation between nanoparticles. In soils, the degradation of surface coating released large of active adsorption sites of Fe3O4 coated starch, resulting in the increase of phosphate adsorption capability.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/35042
Appears in Collections:环境纳米材料研究室_学位论文

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Recommended Citation:
丁程程. 纳米Fe3O4控磷效能的调控及其机理研究[D]. 北京. 中国科学院研究生院. 2010.
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