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

在这个项目中，我们希望从基础胶体科学的角度来研究在水处理过程中从饮用水中去除NOM（天然有机物）的重要课题，这对人类健康至关重要。对于地表水，通常采用阳离子聚电解质（cPEs）来结合和沉淀带负电荷的NOM。尽管这一主题的重要性，但只有很少的研究从根本上解决了它。这是这里采取的方法，我们将采用纯化的腐殖酸（HA; NOM的主要成分）作为模型系统，研究其与不同改性的阳离子（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的q-Chit在NOM去除中非常有希望的结果。它的主要优点是生物相容性和由于易于化学修饰而导致的分子构建的可变性。q-Chit将在本项目中通过适当的合成量身定制，系统地改变电荷密度，Mw和疏水性等参数。在我们的研究中，我们要确定的相行为作为混合比的函数，重点是量化的HA在两相平衡的剩余量。这将通过相互作用热力学（ITC）和通过光，X射线和中子散射形成的复合物的介观结构的全面研究来补充。重要的也是时间的演变系统，要研究的动力学调查的结构变化发生在络合。这种全面的热力学、结构和动力学表征将允许推断cPE的分子结构与其与HA结合的强度之间的系统相关性。基于此，我们将确定哪些分子基序是优化这种相互作用所必需的，大概是阳离子性和疏水性之间的适当平衡，从而控制HA从水中的去除。这些基序将反馈到合成中，以进一步优化cPE。虽然重点是q-Chit，但我们稍后将在该项目中解决季铵化超支化聚乙烯亚胺（PEI）的影响，PEI是一种具有高电荷密度的相当紧凑的球形cPE。将研究其对混合物中的相行为和结构的影响，但重点是与（线性）q-Chit的混合物，因为我们预计这些非常不同的cPE与不同的阴离子HA分子相互作用会产生明显的协同作用。总之，我们期望根据其全面的物理化学特性，对cPEe和HA混合物中普遍存在的条件有一个彻底的基本了解。这将为未来从饮用水中去除NOM的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.