Modified (Bio)polyelectrolytes for Removing Natural Organic Matter (NOM) From Water – A Fundamental Investigation for the Case of Humic Acid as Model NOM

在本项目中，我们希望从基础胶体科学的角度来研究饮用水处理过程中天然有机物质（NOM）的去除这一重要课题，这对人类健康至关重要。对于地表水，通常使用阳离子聚电解质（cpe）来结合和沉淀带负电荷的NOM。尽管这一主题很重要，但很少有研究从基本的角度来解决这一问题。这就是本文采用的方法，我们将采用纯化腐植酸（HA； NOM的主要成分）作为模型体系，研究其与不同改性阳离子（季铵化）壳聚糖（q-Chit）的络合作用。与澳大利亚合作者进行的概念验证测试已经显示出简单q-Chit去除NOM的非常有希望的结果。它的主要优点是生物相容性和由于易于化学修饰而形成的分子的可变性。q-Chit将在该项目中通过适当的合成来量身定制，系统地改变电荷密度、Mw和疏水性等参数。在我们的研究中，我们想确定相行为作为混合比例的函数，重点是量化两相平衡中HA的剩余量。这将由综合研究相互作用热力学（ITC）和通过光、x射线和中子散射对形成的配合物的介观结构进行补充。重要的是系统的时间演化，要通过在络合过程中发生的结构变化的动力学研究来研究。这种全面的热力学、结构和动力学特征将有助于推断cpe分子结构与其与HA结合强度之间的系统相关性。在此基础上，我们将确定哪些分子基序对于优化这种相互作用是必不可少的，可能是阳离子和疏水性之间的适当平衡，从而控制HA从水中去除。这些基序将被反馈到合成中，以进一步优化cpe。虽然重点放在q-Chit上，但我们稍后将在项目中讨论季铵化超支化聚乙烯亚胺（PEI）的效果，PEI是一种相当紧凑的球状cPE，具有高电荷密度。它对混合物中相行为和结构的影响将被研究，但重点是与（线性）q-Chit的混合物，因为我们期望这些非常不同的cpe与各种阴离子HA分子相互作用产生明显的协同作用。综上所述，我们希望基于cPEe和HA的综合物理化学特征，对其混合物的普遍条件有一个彻底的基本理解。这将为从饮用水中去除NOM的未来发展提供良好的科学基础，这是人类当前面临的重大技术挑战之一。

In this project we want to investigate from a fundamental colloid science perspective the important topic of NOM (Natural Organic Matter) removal from drinking water during the water treatment process, which is essential for human health. For surface water typically cationic polyelectrolytes (cPEs) are employed to bind and precipitate the negatively charged NOM. Despite the importance of this topic only few studies have addressed it from a fundamental point of view. This is the approach taken here, where we will employ purified humic acid (HA; main component of NOM) as model system to study its complexation with differently modified cationic (quaternised) chitosan (q-Chit). Proof-of-concept tests carried out with Australian collaborators already showed very promising results of simple q-Chit in NOM removal. Its main advantage are biocompatibility and the variability of the molecular build-up due to the ease of chemical modification. q-Chit will be tailor-made by appropriate synthesis within this project, systematically varying parameters like charge density, Mw, and hydrophobicity. In our study we want to determine the phase behaviour as a function of mixing ratio, with an emphasis on quantifying the remaining amounts of HA in the two-phase equilibrium. This will be complemented by comprehensive studies of the thermodynamics of interaction (ITC) and of the mesoscopic structure of the formed complexes by means of light, x-ray and neutron scattering. Important is also the temporal evolution of the systems, to be studied by kinetic investigations of the structural changes taking place during complexation. This comprehensive thermodynamic, structural and kinetic characterisation shall allow to deduce systematic correlations between the molecular architecture of the cPEs and the strength of their binding to HA. Based on this we will identify which molecular motifs are essential for optimising this interaction, presumably a proper balance between cationicity and hydrophobicity, and thereby control HA removal from water. These motifs will be fed back to the synthesis in order to optimise the cPEs further. While the focus is on q-Chit, we will later in the project also address the effect of quaternised hyperbranched polyethylene imine (PEI), a rather compact, globular cPE with high charge density. Its effect on phase behaviour and structures in mixtures will be studied but with an emphasis on mixtures with (linear) q-Chit as we expect pronounced synergism from having these very different cPEs interact with the diverse anionic HA molecules. In summary, we expect to gain a thorough fundamental understanding of the conditions prevailing in mixtures of cPEe and HA, based on their comprehensive physico-chemical characterisation. This shall deliver a sound scientific basis for future developments in removing NOM from drinking water, one of the big current technological challenges of mankind.