CAS Key Laboratory of Urban Pollutant Conversion, Department of Applied Chemistry, University of Science and Technology of China, Hefei 230026, China.
CAS Key Laboratory of Urban Pollutant Conversion, Department of Applied Chemistry, University of Science and Technology of China, Hefei 230026, China; College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 310036, China.
Environ Int. 2019 Oct;131:105045. doi: 10.1016/j.envint.2019.105045. Epub 2019 Jul 25.
In this work, a thin-film composite forward osmosis (FO) membrane was fabricated on polyethersulfone substrate by interfacial polymerization with naturally-available humic acid (HA) as a stable membrane additive in the support layer. Compared with the pristine polyethersulfone substrate, the incorporation of HA significantly altered the cross-section structure, increased average pore size and porosity of the substrate, leading to a thinner polyamide layer, further increasing the water flux (permeability). Specifically, the FO membrane showed a higher water flux (20 L m h) with the introduction of HA than the membrane synthesized without HA (15 L m h) in the FO mode with 2 M NaCl as draw solution. Moreover, the selectivity of the membrane was improved 45% by dosing 0.8 wt% HA into the substrate, in comparation to the pristine membrane without HA doped. Besides, the average roughness of the polyamide layer was reduced by up to 68% when HA was present in the substrate, which mitigated the fouling potential. Thus, a slower flux decline ratio (60%) was observed for the membrane modified with 0.8 wt% HA than the pristine membrane (~80%). Taken together, our findings shed light on using natural-available HA for effectively and efficiently modifying membrane substrate to simultaneously enhance the permeate-selectivity performance and the anti-fouling behavior in FO membrane process. The fundamental causes of these differences in membrane separation performance and fouling behavior are considered and related to the physical and chemical characteristics of support layer (i.e., porosity and pore size) and polyamide layer (i.e., active layer thickness and roughness) of membranes.
在这项工作中，通过界面聚合在聚醚砜基底上制备了一种薄膜复合正向渗透（FO）膜，其中天然存在的腐殖酸（HA）作为支撑层中的稳定膜添加剂。与原始的聚醚砜基底相比，HA 的掺入显著改变了横截面结构，增加了基底的平均孔径和孔隙率，导致酰胺层更薄，进一步提高了水通量（渗透性）。具体而言，与没有添加 HA 的膜相比（15 L m h），在 FO 模式下，当以 2 M NaCl 作为汲取液时，引入 HA 的 FO 膜表现出更高的水通量（20 L m h）。此外，通过在基底中掺杂 0.8 wt%的 HA，膜的选择性提高了约 45%，与没有掺杂 HA 的原始膜相比。此外，当 HA 存在于基底中时，聚酰胺层的平均粗糙度降低了多达 68%，从而减轻了污染的潜力。因此，与原始膜相比（80%），用 0.8 wt% HA 改性的膜的通量下降率较慢（60%）。总的来说，我们的发现表明，使用天然存在的 HA 可以有效地和高效地修饰膜基底，从而同时提高 FO 膜过程中的渗透选择性性能和抗污染性能。考虑到膜分离性能和污染行为的这些差异的根本原因，并与支撑层（即孔隙率和孔径）和聚酰胺层（即活性层厚度和粗糙度）的物理和化学特性有关。
