Fabrication of polyamide/ceramic composite nanofiltration membrane with polydopamine interlayer for enhanced performance and versatile applications

The growing demand for water and resource recovery drives the need for robust membranes capable of operating in harsh environments. Ceramic membranes offer exceptional solvent and thermal resistance, but fabricating pure ceramic nanofiltration (NF) membranes with nanoscale pore size for salt and small-molecule separation remains energy-intensive and costly. Polyamide (PA)/ceramic composite membranes, formed via interfacial polymerization (IP) on ceramic supports, present a promising alternative. However, large-pore (100–200 nm) tubular ceramic substrates hinder IP due to their superhydrophilicity and poor reaction interface control, often leading to defective PA layers. Here, we introduced a polydopamine (PDA) interlayer to enable uniform PA formation on large-pore ceramics. The PDA interlayer plays a crucial role in facilitating the formation of a continuous and complete PA layer on 200 nm ceramic substrates. The optimized PA/ceramic composite membrane achieved a water permeance of 14.0 L m⁻² h⁻¹ bar⁻¹, 96.1 % rejection of Na₂SO₄, and a molecular weight cut-off of 200 Da. It also demonstrated excellent NF performance in organic solvents, achieving permeances of 1.1 L m⁻² h⁻¹ bar⁻¹ in ethanol and 4.8 L m⁻² h⁻¹ bar⁻¹ in methanol, while effectively rejecting 91.4 % of a dye with a molecular weight of 327.3 Da. Remarkably, the membrane maintained stability under extreme conditions—including organic solvents, temperature up to 80 °C, and pressure of 10 bar—highlighting its potential for demanding industrial applications. This study lays the groundwork for developing robust NF membranes using highly inert ceramic substrates, paving the way for their application in increasingly demanding environments.