胡敏酸-赤铁矿复合纳米颗粒对典型有机污染物的吸附及作用机制

发布时间：2018-04-30 01:00

本文选题：胡敏酸-赤铁矿复合纳米颗粒 + 吸附　；参考：《浙江大学》2017年硕士论文

【摘要】：由于纳米颗粒具有很小的粒径和较大的比表面积,使得这些材料在各领域都有广泛的应用。工程纳米颗粒在土壤与水体修复中已有较多应用,然而当这些工程纳米颗粒进入环境中后会对微生物、植物、动物甚至人体造成毒害作用,因此,研究人员开始将目光转移到天然纳米颗粒。土壤天然纳米颗粒的产生伴随着地球和人类演化的整个过程,与其所处环境更为兼容,这些纳米颗粒可能具有与工程纳米颗粒相似的特性,但是环境风险更小。本研究以胡敏酸包被的纳米赤铁矿为对象,开展了对典型有机污染物五氯酚(PCP)和菲(PHE)的吸附试验,比较了不同胡敏酸种类、胡敏酸包被量以及pH条件对吸附的影响,获得主要结果如下:(1)纳米赤铁矿经胡敏酸包被后,其对PCP和PHE的吸附能力有1-2个数量级的提高。吸附能力与有机污染物的极性有关,对极性较低的PHE的吸附分配系数要明显高于极性高的PCP。通过傅里叶红外光谱、13C核磁共振、元素分析等研究手段发现,胡敏酸包被可以提高纳米赤铁矿表面的疏水性,并且引入较多的有机官能基团,为吸附提供了更多的作用方式。(2)胡敏酸-赤铁矿复合纳米颗粒对PCP和PHE的吸附能力随着胡敏酸包被量的增加而增强。在胡敏酸包被比例相同的情况下,HApeat(Peat Humic acid)包被的纳米赤铁矿对污染物的吸附分配系数高于HAsoii(Soil humic aicid)包被的。比较有机碳标准化分配系数Koc发现,吸附在纳米赤铁矿表面的胡敏酸对PCP和PHE的KOC要高于原胡敏酸,说明纳米赤铁矿会选择性吸附胡敏酸中的某些组分,从而造成胡敏酸的分级作用。胡敏酸的构象改变造成高包被量的胡敏酸-赤铁矿复合纳米颗粒的Koc要低于低包被量的复合纳米颗粒。(3)溶液pH由2到12的变化过程中,胡敏酸-赤铁矿复合纳米颗粒对PCP和PHE的吸附能力都明显降低,尤其是对PCP。疏水作用、氢键作用、静电作用、胡敏酸构象和污染物离解等可能存在机制共同造成在低pH条件下,对PCP和PHE的吸附能力最强,而在高pH条件,吸附能力最弱。低pH下增强的疏水作用、氢键作用等可以弥补颗粒团聚导致的吸附位点的减少。总的来说,胡敏酸的性质变化主导着吸附的整个过程。
[Abstract]:These materials are widely used in various fields because of their small particle size and large specific surface area. Engineering nanoparticles have been widely used in soil and water remediation. However, when they enter the environment, they can cause toxicity to microorganisms, plants, animals and even human beings. The researchers began to shift their attention to natural nanoparticles. The formation of soil natural nanoparticles is accompanied by the whole evolution process of the earth and human being, which is more compatible with the environment. These nanoparticles may have similar characteristics to engineering nanoparticles, but the environmental risk is lower. In this study, Nano-hematite coated with Hu Min acid was used to study the adsorption of typical organic pollutants, pentachlorophenol (Hu Min) and phenanthrene (PHE). The effects of different kinds of Hu Min acids, the amount of Hu Min acid coating and pH on the adsorption were compared. The main results are as follows: (1) the adsorption of PCP and PHE on hematite nanocrystalline was improved by 1-2 orders of magnitude after it was coated with Hu Min acid. The adsorption capacity is related to the polarity of organic pollutants, and the adsorption partition coefficient of PHE with lower polarity is obviously higher than that of PCPs with high polarity. By means of Fourier transform infrared spectroscopy (FTIR), 13C NMR and elemental analysis, it was found that Hu Min acid coating could improve the hydrophobicity of hematite nanocrystalline surface and introduce more organic functional groups. The adsorption ability of Hu Min and hematite composite nanoparticles for PCP and PHE increased with the increase of the amount of Hu Min acid coating. Under the same Hu Min acid coating ratio, the adsorption and partition coefficients of hematite coated with Hu Min acid are higher than those coated by HAsoii(Soil humic acid. Compared with the standard partition coefficient of organic carbon (Koc), it was found that the KOC of PCP and PHE adsorbed on the surface of nano-hematite was higher than that of the original Hu Min acid, indicating that nano-hematite selectively adsorbs some components of Hu Min acid. As a result, Hu Min acid is classified. The conformational change of Hu Min acid resulted in the Koc of high encapsulated Hu Min acid-hematite composite nanoparticles being lower than that of low encapsulated Hu Min acid / hematite composite nanoparticles. The pH of the solution varied from 2 to 12. The adsorption ability of Hu Min and hematite composite nanoparticles to PCP and PHE was obviously decreased, especially for PHE. Hydrophobic interaction, hydrogen bond interaction, electrostatic interaction, Hu Min conformation and pollutant dissociation may result in the strongest adsorption capacity of PCP and PHE at low pH, but the weakest at high pH. The increase of hydrophobicity and hydrogen bonding at low pH can compensate for the decrease of adsorption sites caused by particle agglomeration. In general, the property change of Hu Min acid dominates the whole process of adsorption.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X505;O647.3

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