Constructing a tannic-Fe interlayer via a simple in-situ method to enhance the filtration performance of hollow fiber organic solvent nanofiltration membranes

Hollow fiber (HF) organic solvent nanofiltration (OSN) membranes have the advantage of simple production and large packing density, which make them promising for organic solvent recovery. However, current HF OSN membranes still suffer from poor separation performance. To overcome this problem, in this work, we proposed a simple method to in-situ construct a tannic (TA)-Fe interlayer on the surface of an HF ultrafiltration membrane. In this way, we could effectively manipulate the interfacial polymerization (IP) reaction between m-phenylenediamine (MPD) and trimesoyl chloride (TMC), thus successfully boosting the filtration performance of the polyamide (PA) HF OSN membrane. We highlight that TA molecules were enriched on the surface of the HF ultrafiltration membrane during the phase inversion process, which is beneficial for the in-situ construction of a TA-Fe interlayer via immersing this HF substrate in FeCl3 solution. Consequently, we effectively simplified the fabrication procedure for constructing an interlayer. With the aid of the TA-Fe interlayer, the HF OSN membrane obtained higher crosslinking degree and better filtration performance. The optimized HF OSN membrane achieves an ethanol permeance of 14.7 L m- 2 h-1 MPa- 1 and a Rhodamine B (RDB, 479 Da) rejection of 98.6 %. Additionally, it displays excellent operation stability performance. It remains an ethanol permeance of 8.6 L m- 2 h-1 MPa- 1 and an RDB rejection of 99.4 % after a continuous cross-flow filtration for over 1000 min. Also, it shows excellent chemical stability performance, corresponding to an extension of less than 4 % after soaking in ethanol for 8 d. This research shows a simple approach for the fabrication of interlayered thin film composite (iTFC) HF OSN membranes.