Enhancing interface compatibility of UiO-66-NH2 and polyamide by incorporating dopamine into thin film nanocomposite membranes

The introduction of nanoparticles into nanofiltration (NF) membranes is an effective approach to improve the NF performance as the construction of water channels in the nanoparticles. However, the poor compatibility be-tween polymer matrix and nanoparticles is a crucial issue that attracts numerous researchers. In this paper, dopamine (DA) molecule was introduced into the aqueous solution for preparing NF membranes by interfacial polymerization to build a bridge between polyamide matrix and nanoparticles (polydopamine coated UiO-66-NH2, U@PD) for its self-polymerization and high reactive activity of abundant of hydroxyl and amino groups. It was found that the addition of DA in aqueous reaction phase solution effectively reduced the membrane surface roughness, anchored more U@PD nanoparticles, improved the hydrophilicity of the membrane, and participated in the interfacial polymerization reaction to crosslink the nanoparticles and the polyamide matrix. The DA introduced TFN membrane achieved high water permeance (13.87 L.m(-2).h(-1).bar(-1)) and Na2SO4 rejection (97.96%) with DA concentration of 0.3 g/L, U@PD incorporating amount of 0.3 wt%, cross-linking reaction time of 45 min, and pH of 8.5. Additionally, the as-prepared membrane had an excellent selectivity of Cl-/SO42-(alpha = 45.85), which was higher than that of the membrane without DA crosslinking agent (alpha = 14.40). It is concluded that the addition of DA in the interfacial polymerization aqueous solution can effectively repair the defects between the nanoparticles and the polymer, thus provide a new idea for seawater desalination.

Automated summary

The addition of dopamine in the interfacial polymerization aqueous solution effectively repairs the defects between nanoparticles and polymers, improving the performance and selectivity of the nanofiltration membranes. The membranes with dopamine exhibit reduced surface roughness, increased nanoparticle anchoring, improved hydrophilicity, and achieved high water permeance and Na2SO4 rejection. Furthermore, the membranes show excellent selectivity for Cl-/SO42-.