Micropatterned Thin-Film Composite Poly(piperazine-amide) Nanofiltration Membranes for Wastewater Treatment

The sustainable growth of industries that consume a large amount of fresh water relies on developing energy-efficient wastewater treatment processes. Nanofiltration (NF) has been widely considered for such purposes; however, the fabrication of highly permeable NF membranes while maintaining a high removal rate of ions and organic matter remains a big challenge. Here, we fabricated micropatterned thin-film composite (TFC) NF membranes using a two-step process. First, a hydrogel-facilitated phase separation (HFPS) method was used to prepare micropatterned poly(ether sulfone) (PES) substrates. Then, a thin dense polyamide (PA) film was formed on top of the patterned PES substrates using an interfacial polymerization reaction between piperazine (PIP) and trimesoyl chloride (TMC) monomers. The fabricated TFC membranes, micropatterned and unpatterned, possessed a high negatively surface charge, hydrophilicity, and a smooth surface roughness. Moreover, the filtration performance of the fabricated membranes was evaluated through the separation of different salts (e.g., MgSO4, Na2SO4, and NaCl), reactive black 5 dye, and methyl orange dye, and the treatment of real oil sands produced water. The TFC-patterned membrane with 0.25 wt % PIP showed an ∼96 increase in the water flux compared with an unpatterned one with a less than 10% reduction in the separation performance for the aforementioned solutes due to the increase in the surface area.