Polydopamine Bilayer Nanofiltration Membranes with Excellent Resistance to Delamination

摘要

Bilayer nanofiltration (NF) membranes tend to delaminate and have poor stability when applied in organic solvents due to their bi-layered structure. In this study we prepared two types of polydopamine (PDOPA) modified NF membranes including PDOPA-TMC (trimesoyl chloride)/PSF and PDOPA/PIP(Piperazine)-TMC/PSF NF membranes on polysulfone (PSF) ultrafiltration membranes via interfacial polymerization based on PDOPA’s specialized molecular structure and high adhesion property. The separation performance and stability of the NF membranes were investigated. Both the polyester bonds of the PDOPA bilayer membranes and the bioadhesion of the PDOPA were simultaneously beneficial to improving the structure and chemical stabilities of the bilayer membranes. After soaking both the PDOPATMC/ PSF and PDOPA/PIP-TMC/PSF NF membranes in ethanol solvent for 12 days, the rejection of Congo red only decreased by 1.8% (original, 99.9%) and 1.2% (original, 99.9%), respectively. For the PDOPA/ PIP-TMC/PSF NF membrane, the rejection of Na_2SO_4 was only reduced by 1.6% (original, 98.5%). Moreover, the separation performances of both the PDOPA-TMC/PSF and PDOPA/PIP-TMC/PSF NF membranes were still excellent after soaking in a sodium hypochlorite solution (50ppm) for 240 h (12,000ppm·hours). The NF membranes thus exhibited long-term structural stability in ethanol and excellent chemical stability in the sodium hypochlorite solution. In particular, no delamination was observed in the above experiments, which is significant for their use in the wastewater treatment field.