典型纳米材料存在下水中重金属离子的去除机制及腐殖酸的影响

发布时间：2018-08-11 17:24

【摘要】：纳米材料因具有大比表面积、丰富的含氧官能团等优点,被认为是水中有机污染物和重金属净化的优良吸附剂。环境中广泛存在的天然有机质(NoM)会通过各种相互作用吸附到纳米材料表面上,不仅会改变颗粒物在环境中的迁移、转化及归宿,同时也可能会影响纳米材料对重金属离子的吸附,从而改变环境中重金属的迁移、转化及归宿。因此,本文研究了几种典型纳米材料(包括纳米碳管和纳米氧化物)存在下Cu2+、Zn2+、Pb2+、Cd2+等重金属离子的去除机制以及腐殖酸改性纳米氧化物吸附Cu2+离子的规律及机理研究,取得了以下主要创新性结论。(1)发现纳米材料存在下水中重金属离子的去除机制主要是重金属自身的沉淀作用,而不是纳米材料的吸附作用。主要证据包括不同溶液pH值下的去除率曲线和沉淀曲线重合,不同pH值下的去除率曲线不受吸附剂剂量、重金属初始浓度的影响。并初步探明以往研究得到纳米材料能高效吸附去除重金属离子的表观结论主要原因是忽略了反应前后溶液pH值的变化情况或纳米材料在生产制造过程中本身所含有的杂质会与重金属离子产生沉淀作用。(2)Cu2+离子在腐殖酸改性纳米氧化钛和Y-纳米氧化铝上的吸附容量与腐殖酸改性量成正相关,吸附能力则与改性后腐殖酸中羧基在总官能团中的占比成正相关,说明腐殖酸改性能显著增强纳米氧化物对Cu2+离子的吸附。探明其吸附机制主要是通过负载到纳米氧化物表面的含氧官能团,特别是羧基含氧官能团吸附Cu2+离子。与纳米氧化铝相比,纳米氧化钛不仅能吸附更多的腐殖酸,而且主要是通过羟基结合腐殖酸,导致改性纳米氧化钛中羧基在总官能团中占比增大。因此,腐殖酸改性纳米氧化钛对Cu2+离子不仅有更大的吸附容量,还有更强的吸附能力。
[Abstract]:Nanomaterials are considered as excellent adsorbents for the purification of organic pollutants and heavy metals in water due to their large specific surface area and abundant oxygen functional groups. (NoM), a natural organic matter widely existing in the environment, is adsorbed onto the surface of nanomaterials through various interactions, which will not only change the transport, transformation and fate of particulate matter in the environment. At the same time, it may affect the adsorption of heavy metal ions by nanomaterials, thus changing the migration, transformation and fate of heavy metals in the environment. Therefore, in the presence of several typical nano-materials (including carbon nanotubes and nano-oxides), the removal mechanism of heavy metal ions such as Cu2 _ (2) Zn _ (2) and Pb _ (2) O _ (2) CD _ (2) and the regularity and mechanism of humic acid-modified nano-oxides adsorbing Cu2 ions were studied. The main innovative conclusions are as follows: (1) it is found that the removal mechanism of heavy metal ions in water under the presence of nanomaterials is mainly the precipitation of heavy metals themselves rather than the adsorption of nanomaterials. The main evidences include the coincidence of the removal rate curve and precipitation curve under different pH values, and the removal rate curves under different pH values are not affected by the concentration of adsorbent and the initial concentration of heavy metals. The main reason is that the change of pH value of solution before and after the reaction or the content of nanomaterials in the process of production and manufacture are ignored. Some impurities can precipitate with heavy metal ions. (2) the adsorption capacity of Cu2 ions on humic acid-modified nano-titanium oxide and Y- nano-alumina is positively correlated with the amount of humic acid modification. The adsorption capacity was positively related to the proportion of carboxyl groups in the total functional group of the modified humic acid, which indicated that the modified humic acid could significantly enhance the adsorption of Cu2 ions on nano-oxides. It is found that the adsorption mechanism is mainly through the adsorption of Cu2 ions by the oxygen-containing functional groups loaded on the surface of nano-oxides, especially the carboxyl oxygen-containing functional groups. Compared with nano-alumina, nano-titanium oxide can not only adsorb more humic acid, but also increase the proportion of carboxyl group in the total functional group of modified nano-titanium oxide mainly through hydroxyl binding humic acid. Therefore, humic acid-modified nano-titanium oxide not only has a larger adsorption capacity for Cu2 ions, but also has a stronger adsorption capacity.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1

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