木质膜耦合聚合物膜的重力驱动膜过滤系统增强水源水中重金属的去除及机制

针对聚合物膜的重力驱动膜过滤系统(gravity-driven membrane filtration system，GDM)对水源水中重金属去除效率低的问题，将其与木质膜(wood membrane，WM)耦合，以环保且廉价的方式提高重金属的去除效率。本研究比较了木质膜耦合聚合物微滤(microfiltration，MF)膜的GDM系统(GDM1)和聚合物微滤膜GDM系统(GDM2)对水源水中重金属的去除效能及机制。与GDM2相比，GDM1系统在木质膜的作用下，其微滤膜(GDM1-MF)上的生物膜更薄并呈现出更疏松的网状结构，因此，膜阻力更低，稳定通量更高。稳定运行后，GDM1系统对水中Fe、Mn和Cu的去除率分别达到67%、43%和59%，均高于GDM2(64%、15%和36%)。这是由于GDM1系统生物膜胞外聚合物(extracellular polymeric substances，EPS)中蛋白含量以及—OH和—COOH基团更多，更有利于截留重金属。此外，GDM1-MF中存在更多的锰氧化细菌、酸杆菌门Acidobacteriota和黄杆菌属Flavobacterium，促进了Mn和Cu的去除。本研究为利用GDM系统去除水中重金属提供了新的思路和方法，对推动利用GDM系统处理重金属污染水源水的应用具有重大意义。

Gravity-driven filtration system based on wood membrane coupled with polymer membrane strengthening heavy metal removal from source water: insight of performance and mechanism

Gravity-driven membrane filtration system (GDM) with polymer membrane has a disadvantage of low efficiency of heavy metals removal from water. To address this problem, it is coupled with wood membrane (WM) to promote heavy metal removal in an environmentally friendly and low-cost way. In this study, we compared two microfiltration-based GDM systems, one was the wood membrane coupled with polymeric microfiltration (MF) membrane (GDM1), and the other was polymeric microfiltration membrane (GDM2) only. Their removal of heavy metals from water was compared and the underlying mechanism was further investigated. The results showed that, compared with GDM2, the GDM1 system with wood membrane had a thinner biofilm thickness with more sparse reticular structures on the microfiltration membrane (GDM1-MF). Thus, GDM1 system exhibited a lower membrane resistance and a higher stable flux. During the stable operation stage, the GDM1 system decreased 67%, 43% and 59% of Fe, Mn and Cu in water, respectively, which were much better than GDM2 system (64%, 15% and 36%, respectively). This is because the coupling of wood membrane increased the protein content as well as —OH and —COOH groups of the extracellular polymer (EPS) in the biofilm, which contributed to more heavy metal retention in the GDM1 system. In addition, the presence of more manganese-oxidizing bacteria, Acidobacteria phylum and Flavobacter spp. in GDM1-MF promoted the removal of Mn and Cu. This study provides a new insight into the removal of heavy metals in water by GDM system, which is of great significance to promote the application of GDM system in treating heavy metal contaminated water.