Ca2+离子原位改性TFC正渗透膜优化制备与抗污染机理研究

Reclamation and reuse of municipal wastewater has been recognized as an important way to solve the problems of water resource shortage and water environment pollution. In order to address the membrane fouling issue occurred in forward osmosis (FO) process for wastewater reclamation, based on the systematic analysis of membrane fouling behavior of TFC membrane, the sequestration of carboxyl groups on the polyamide layer of TFC membrane is proposed as the guidance in this project, and it is put forward to modify the TFC membrane via in-situ Ca2+ addition during the reaction of interfacial polymerization to improve its antifouling ability in wastewater reclamation. The main research contents include the following aspects. Firstly, the effect of in-situ Ca2+ addition on the interfacial properties of polyamide active layer of the TFC membrane will be explored, and an optimized preparation method of the in-situ Ca2+-modified TFC membrane will be established. Secondly, the dynamic adsorption/desorption behavior of typical organic components in wastewater on the surface of polyamide layer, as well as the corresponding microscopic mechanism in terms of interfacial interaction force will be analyzed, with the purpose to clarify the anti-organic fouling mechanism of the modified TFC membrane. Meanwhile, the role played by Ca2+ and Mg2+ in the formation of biofouling layer on the surface of TFC membrane is to be revealed, and the anti-biofouling mechanism of the in-situ Ca2+-modified TFC membrane will be clarified. Lastly, the physicochemical stability of the in-situ Ca2+-modified TFC membrane will be systematically evaluated, and the membrane fouling characteristics of the modified TFC membrane in FO process for wastewater reclamation will be analyzed, thus a long-term stable operation scheme of modified membrane can be constructed. The research results can provide theoretical and technical support for the efficient reclamation and reuse of municipal wastewater based on FO technology.

城镇污水再生回用是解决水资源短缺与水环境污染问题的重要途径。针对正渗透技术应用于污水再生领域出现的膜污染问题，本项目提出了以抑制TFC正渗透膜聚酰胺活性层表面羧酸基团作为切入点，通过在界面聚合反应中原位掺加Ca2+离子对TFC正渗透膜进行抗污染改性的科研设想。研究内容：解析Ca2+离子原位掺加对聚酰胺活性层界面特性的作用规律，建立Ca2+离子改性TFC正渗透膜的优化制备方法；探讨污水中典型有机物组分在聚酰胺活性层表面的动态吸附/解吸规律与微观力学作用机制，阐明改性TFC正渗透膜的抗有机污染机理；揭示进水中Ca2+、Mg2+离子在膜表面生物污染层形成中的作用，明确改性TFC正渗透膜的抗生物污染机理；系统评价Ca2+离子原位改性TFC正渗透膜的物化稳定性，阐明城镇污水对改性TFC正渗透膜的膜污染特性，构建改性膜的长效稳定运行方案。研究成果可为基于正渗透技术的污水高效再生回用提供理论和技术支持。

城镇污水再生回用是解决水资源短缺与水环境污染问题的重要途径。针对正渗透技术应用于污水再生领域出现的膜污染问题，本项目提出了以抑制TFC正渗透膜聚酰胺活性层表面羧酸基团作为切入点，通过在界面聚合反应中原位掺加Ca2+离子对TFC正渗透膜进行抗污染改性的科研设想。解析了Ca2+离子原位掺加对聚酰胺活性层界面特性的作用规律，建立了Ca2+离子改性TFC正渗透膜的优化制备方法。发现在水相单体中添加1.0 wt.% CaCl2时，改性膜（TFC-Ca（1.0））表面羧基密度从28.9±0.8降低到16.9±0.5 nm−2，但膜表面亲水性增加、粗糙度降低，同时由于电中和效应膜表面电负性从-28.6±1.2降低到-19.4±0.9 mV，改性膜无论是在正渗透模式下还是在反渗透模式下，均表现出良好的抗污染性能。考察了污水中典型有机物在正渗透过程中的膜污染特性，发现改性膜表面累积的有机物与二价阳离子量明显减少。TFC-control膜和TFC-Ca（1.0）膜的海藻酸钠污染层厚度分别为14.64±0.27和9.62±0.43 µm，相应粘附作用能则由-18.13增加到3.98 mJ/m2（由负值变为正值），从界面自由能角度阐明了Ca2+离子原位改性TFC膜的抗有机污染机理。进一步，发现进料液中二价阳离子，尤其是Ca2+的存在，会加重TFC膜上大肠杆菌和金黄色葡萄球菌产生的膜污染；通过在界面聚合反应中原位添加羧基化壳聚糖（CCTS）调控TFC膜表面羧基密度，发现尽管TFC-CS膜亲水性提高、表面粗糙度降低，但膜污染更为严重。据此明确了二价阳离子存在下膜表面羧基官能团在微生物污染中的关键作用，并揭示了Ca2+离子原位改性TFC膜降低膜表面羧基密度进而减缓细胞粘附的抗微生物污染机理。研究成果可为抗污染TFC正渗透膜的简易制备及其在污水再生回用中的高效应用提供技术支持。