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颗粒物及有机物对Al13 稳定性及形态转化的影响
Alternative TitleEffects of particles and organic matters on the stability and morphological transformation of Al13
焦茹媛
Subtype博士后
Thesis Advisor杨敏 ; 王东升
2019-06
Degree Grantor中国科学院生态环境研究中心
Place of Conferral北京
Degree Name理学
Degree Discipline生态学
KeywordAl13,铝形态转化,颗粒物,有机物,微界面作用过程 Al13, Transformation Of Al Species, Particles, Organic Mattter,micro-interfaciAl Interaction Process
Abstract

      本研究针对聚合氯化铝混凝剂在混凝过程中的形态转化对混凝效率的影响,以聚合氯化铝中优势形态Al13 为研究对象,首先研究了纯体系不同pH 条件下Al13 形态的稳定性,以此为基础,深入探讨了SiO2 存在条件下,Al13 在颗粒物表面原位聚集的微界面作用过程,通过对絮体的组成及表面形态进行表征和分析,深入探究Al13 原位聚集过程与SiO2 失稳凝聚过程之间的微观作用机制。此外,通过研究不同形态结构有机物对Al13 聚集、解聚及络合特性的影响,探讨了有机物存在条件下对Al13 形态转化规律的影响,同时深入探究了Al13 与不同官能团有机物的络合效应关系,阐明了Al13 对不同官能团的选择性作用效能及配位络合模式。得到的主要结论如下:
      (1)pH 对Al13 溶液中铝形态影响显著。pH 在5 以下时,溶液中基本以Al13形态存在;随着pH 增加至5.5 以上至中性范围,Al13 逐渐大量聚集形成Al13 聚集体,作为Al13 向氢氧化铝转化的中间态存在。随着pH 的增高,Al13 聚集体粒径逐渐增大,聚集程度逐渐增强。当pH 升至中性条件时,Al13 溶液中形成了含有上百个Al13 分子的Al13 聚集体。
      (2)颗粒物存在条件下,由于Al13 吸附在颗粒物表面,阻止了Al13 和OH-之间自由反应,因此Al13 转变为氢氧化铝程度减弱,而更多地停留在Al13 聚集体形态。中碱性条件下,Al13 高效去除SiO2 颗粒物的混凝路径为:Al13 首先均匀地吸附到SiO2 表面,然后Al13 在颗粒物表面逐步形成原位的聚集,提高了颗粒物之间的粘附效果,并发挥了架桥作用。与此同时,由于Al13 及Al13 聚集体在颗粒物表面均匀分布,因此颗粒物间的有效碰撞几率增大,促进SiO2 颗粒之间凝聚成大而紧密的絮体,从而提高颗粒物在混凝过程中的去除效率。
      (3)有机物的存在,首先会促进一部分Al13 解聚为低聚体,低聚体再与有机物产生络合效应;与此同时,一些解聚后的铝的低聚体会发生一定程度的再聚合,形成髙聚态铝与有机物的络合形态。pH=6~7 条件下,单齿及双齿络合态均最为丰富,其中,单齿配合物的形成可能是混凝沉淀中有机物与Al 络合的主要形态。由于羧基(-COOH)与羟基(-OH)相比,更容易脱质子与金属形成配位络合,而水解铝会优先选择与芳香结构的有机物络合,因此带羧基有机物更容易混凝去除。
(4)有机物的加入,均一定程度上促进Alc 含量的增加。通过核磁共振检测,发现形成的Alc 主要聚合形态可能是Al30,其原因可能是有机物的加入促进了一部分Al13 降解为低聚态,构成了Al30 生成的基本条件,某一条件下,一些解聚后的铝的低聚体会发生一定程度的再聚合。然而,有机物存在条件下Al13 向Al30 形态的转化仍需要进一步验证及研究。

Other Abstract

      In order to clarify the species transformation of PACl during coagulation process and its effect on coagulation efficiency, Al13 as the most valuable component in PACl was chose in this study. Firstly, the stability of Al13 in pure system was studied. Based on the results, the in situ aggregation behavior of Al13 on the particle (SiO2) surface and its micro-interfacial process were discussed by detecting the composition and the surface morphology of flocs.In addition, the complexation behavior of Al13 and organic matter with different function groups were also studied. The influence of organic matter on Al species transformation was illustrated.The main conclusions are as follows:
      (1) pH has a significant effect on the Al species distribution of Al13 solution.When the pH value was below 5, Al13 could exists steadily in the solution.When the pH value was above 5.5 to the neutral range, Al13 gradually aggregated intoAl13agg,which existed as the intermediate state from Al13 to aluminum hydroxide.With the raising of pH, the particle size and aggregation degree of Al13agg gradually increased. Al13agg contained hundreds of Al13 molecules in the solution of Al13 when the pH value was at the neutral condition.
      (2) In the presence of particles, Al13 was adsorbed on the surface of particles,which prevented the free reaction between Al13 and OH-, so the transforming degree fromAl13 into aluminum hydroxide was weakened. Under the neutral and alkaline conditions, the coagulation pathway of SiO2 effectively removal by Al13 was as follows: Al13 firstly uniformly adsorbed to the surface of SiO2, and then Al13 gradually aggregated in situ on the surface of particles, improving the adhesion effect between particles. Meanwhile, because Al13 and Al13agg uniformly distributed on the surface of particles, the effective collision probability between particles increased, which promoted the formation of large and compact floc between SiO2 particles. It is whythe removal efficiency of particles in the coagulation process was improved .
      (3) The presence of organic compounds first promoted the depolymerization of Al13 into oligomers, and then the oligomers was complexed with organic compounds. Meanwhile, some oligomers might repolymerization, forming a complex form of high poly aluminum and organic compounds. At pH 6 to 7, the complex states with single tooth and double teeth were the most abundant, among which the formation of single tooth complex might be the main form flocs. Compared with hydroxyl group (-COOH), carboxyl group (-OH) is easier to deproton and form coordination complexation with metal, while polyaluminum will preferentially complexate with organic compounds with aromatic structure, so it is easier to coagulate and remove organic compounds with carboxyl group.
      (4) The addition of organic compounds promoted the increase of Alc content in Al13 solution to some extent. It was found that the main polymerization form of Alc might be Al30. it was because the addition of organic compounds promotes the degradation of Al13 into oligomer, which constitutes the basic conditions for the formation of Al30. Under a certain condition, the Al oligomer will undergo a certain degree of repolymerization. However, the transformation of Al13 to Al30 in the presence of organic matter still needs further verification and research.

Pages80
Language中文
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/42221
Collection环境水质学国家重点实验室
Recommended Citation
GB/T 7714
焦茹媛. 颗粒物及有机物对Al13 稳定性及形态转化的影响[D]. 北京. 中国科学院生态环境研究中心,2019.
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