Cu-MOF-Polydopamine-Incorporated Functionalized Nanofiltration Membranes for Water Treatment: Effect of Surficial Adhesive Modification Techniques

Nanofiltration (NF) membranes have been used for different applications in water treatment. In this work, we studied two facile surficial adhesive functionalization processes using polydopamine (pDA) and a metal-organic framework (MOFs) and investigated their individual and synergistic effects on membrane rejection, permeability, and antifouling properties. The copper MOF nanoparticles (Cu-MOF) were synthesized and incorporated with the pDA for surface coating of NF membranes using two different static (dip-coating) and dynamic (filtration-assisted) fabrication processes. All of the functionalized membranes were characterized completely, and the effects of pDA and Cu-MOF separately and together on the membrane physicochemical properties were identified. The results showed that the surface functionalization by only pDA enhanced the dye rejection from 22% (blank) to 98% (pDA-functionalized membrane). The dip-coating approach resulted in uniform polymerization of pDA on the membrane surface, while the filtration-assisted technique generated a deficient pDA layer. The incorporation of Cu-MOF into the pDA layer improved the permeability of the pDA-functionalized membrane by increasing the hydrophilicity of membranes and providing more water pathways due to the porous structure of MOFs. In addition, the molecular dynamics (MD) investigation of MOF-functionalized membranes revealed the role of embedded Cu-MOF charge repulsion mechanisms in the rejection of anionic and cationic dyes.

Automated summary

In this study, two facile surficial adhesive functionalization processes using polydopamine (pDA) and a metal-organic framework (MOFs) were investigated for their effects on membrane rejection, permeability, and antifouling properties. The results showed that surface functionalization by pDA alone significantly enhanced dye rejection, while the incorporation of Cu-MOF into the pDA layer improved membrane permeability and provided more water pathways. Molecular dynamics investigations revealed the role of embedded Cu-MOF charge repulsion mechanisms in dye rejection.