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，我们想从基础胶体科学的角度来研究饮用水处理过程中对人类健康至关重要的天然有机物(NOM)的去除这一重要课题。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，但很少有研究从根本上解决这一问题。这就是我们所采用的方法，我们将使用纯化的腐植酸(HA；NOM的主要成分)作为模型体系，研究其与不同修饰的阳离子(季铵)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，简单的Q-Chit在去除NOM方面的结果非常有希望。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筑的可变性。Q-Chit将在这个项目中通过适当的合成来量身定做，系统地改变参数，如电荷密度、MW和疏水性。在我们的研究中，我们希望确定相行为作为混合比的函数，重点是量化两相平衡中HA的剩余量。此外，还将通过光、X射线和中子散射对相互作用热力学(ITC)和形成的络合物的介观结构进行全面研究。体系的时间演化也很重要，要通过络合过程中发生的结构变化的动力学研究来研究。这种综合的热力学、结构和动力学表征将允许推断CPE的分子结构和它们与HA的结合强度之间的系统关联。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，从而控制水中HA的去除。这些基序将反馈给合成，以进一步优化CPE。虽然重点放在Q-Chit上，但我们稍后还将讨论季节化超支化聚乙烯亚胺(PEI)的影响，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，但重点是带有(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显着的协同效应。综上所述，我们希望在全面的物理化学特征的基础上，彻底地从根本上了解cPEe和HA混合物中的普遍情况。这将为未来从饮用水中去除NOM的发展提供坚实的科学基础，这是人类目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.