水环境中NOM-Mn(III)胶体的形成机理和稳定性研究

FORMATION AND AGGREGATION OF NOM-Mn(III) COLLOIDS IN AQUEOUS SOLUTIONS

李倩倩

11649133

硕士

环境科学与工程

刘崇炫

2018-05-28

2018-07-09

哈尔滨工业大学

深圳

Mn(III)与天然有机质（Natural Organic Matter，NOM）的络合现象近年来 受到了越来越多的关注。当前，学术界对 NOM-Mn(III)溶解络合物的形成、化 学性质、环境行为等展开了广泛研究，但是忽视了对 NOM-Mn(III)胶体络合物 的形成和稳定性方面的研究。研究 NOM-Mn(III)胶体在水环境中的形成和稳定 性有助于更好地理解 Mn 和碳的生物地球化学循环以及定量地预测胶体携带污 染物的迁移转化规律。为了填补这一知识缺口，我们以腐殖酸（humic acid, HA） 为代表性的 NOM，系统研究了 HA-Mn(III)胶体在一系列环境相关条件下的形成 和稳定性机理。具体而言，我们首先在实验室内原位形成 HA-Mn(III)胶体，然 后借助一系列先进表征技术（DLS、zeta 电位、ATR-FTIR、XPS、Cs-corrected STEM）解析了胶体的表面性质和微观结构，进而研究了它们在水环境中的稳定 性行为。我们最后将实验室内建立的胶体稳定性理论应用到实际天然水体中， 考察了 HA-Mn(III)胶体在河水和地下水中的稳定性行为。我们的结果表明，C/Mn 摩尔比和 HA 的来源（Aldrich HA（AHA）和 Pahokee peat soil HA（PPSHA））是影响 HA-Mn(III)胶体形成及其稳定性行为的关键因 素。不论 HA 的来源如何，HA-Mn(III)胶体的含量以及稳定性都会随着 C/Mn 摩尔比（0-50）的增加而不断增加。对其进行理论计算可以发现，临界絮凝浓 度（Critical coagulation concentration, CCC）和 zeta 电位（ tan h ( / 4) 0 4 a ）之间 具 有 很 好 的 线 性 关 系 （ R2 > 0.97 ） , 这 表 明 DLVO （Derjaguin-Landau-Verwey-Overbeek）力和非 DLVO 力共同决定 HA-Mn(III)胶 体的稳定性。对于特定的 C/Mn 摩尔比，PPSHA-Mn(III)胶体比 AHA-Mn(III)胶 体更加稳定，这可能是由于 PPSHA-Mn(III)胶体具有更强的静电作用、水合作 用、空间位阻斥力等。实验最后一步研究了 HA-Mn(III)胶体在自然水体环境中 的稳定性，结果表明 HA-Mn(III)胶体在地表水中具有较高的稳定性，但是在地 下水与海水交互带的模拟水中稳定性较低（大量团聚）。综上所述，我们的研究从新的视角深入研究了 NOM-Mn(III)胶体的形成和 稳定性行为，从基础上扩展了我们对 Mn(III)与 NOM 相互作用的认识。这对我 们深入理解对污染物、有机物和微量金属的命运和归宿具很大影响的 C 和 Mn 的生物地球化学循环提供了理论见解。

Soluble Mn(III) species stabilized by natural organic matter (NOM) plays a crucial role in many biogeochemical processes in natural environments. Much of current knowledge has concerned on the occurrence and chemistry of soluble NOM-Mn(III) complexes, and less on the formation and stability of NOM-Mn(III) colloids. The later is important for understanding the biogeochemical cycling of carbon and Mn, and for predicting the fate and transport of colloid-associated contaminants, nutrients, and trace metals. In this work, we characterized the chemical and physical properties of humic acid (HA)-Mn(III) colloids formed over a range of environmentally relevant conditions, and investigated their subsequent aggregation and stability behaviors. Specifically, we first formed HA-Mn(III) colloids in the laboratory, and then characterized the surface properties and microscopic structure of the colloids by means of a series of advanced characterization techniques including DLS, zeta potential, ATR-FTIR, XPS, Cs-corrected STEM, and then study their stability behavior in aqueous solutions. Finally, we applied the colloidal stability mechanisms established in the laboratory to more complex natural water, and investigated the stability behavior of HA-Mn(III) colloids in surface water and groundwater. Our results demonstrate that molar C/Mn ratios and different HA types (Aldrich HA (AHA) and Pahokee peat soil HA (PPSHA)) are the critical variables influencing the properties of HA-Mn(III) colloids and their stability behaviors. Both the amount and the stability of HA-Mn(III) colloids increased with increasing initial molar C/Mn ratios from 0 to 50, regardless of the HA types. The correlation (R2 > 0.97) between the critical coagulation concentration (CCC) and zeta potential ( tan݄Ͷ ܽɗͲȀͶ ሻ suggests that both DLVO-type and non-DLVO interactions are responsible for the enhanced stability of HA-Mn(III) colloids. For a given C/Mn ratio, PPSHA-Mn(III) colloids are significantly more stable against aggregation than AHA-Mn(III) colloids likely due to the stronger electrostatic interactions, hydration interactions, and steric hindrance. Further examination using natural aqueous matrices indicates that the HA-Mn(III) colloids are highly stable in surface river water but are unstable (extensive aggregation) in solutions mimicking water in a groundwater-seawater interaction zone. Overall, our study provides new insights on the formation and stability of NOM-Mn(III) colloids that are important for understanding colloidal behaviors in aquatic environments. The results provided valuable insights for the understanding of C and Mn geochemistry in aqueous systems that have strong implication on the fate and transport of contaminants, nutrients, and trace metals.

NOM-Mn(III)胶体 C/Mn比 HA来源 胶体形成 胶体稳定性

NOM-Mn(III) colloids C/Mn ratios HA isolates colloidal formation colloidal stability

中文

联合培养

哈尔滨工业大学

李倩倩. 水环境中NOM-Mn(III)胶体的形成机理和稳定性研究[D]. 深圳. 哈尔滨工业大学,2018.