Mussel-inspired modification of PPS membrane to separate and remove the dyes from the wastewater

A novel coating with stable and excellent wettability is architecturally constructed on the surface of polyphenylene sulfide (PPS) membrane via co-deposition with polyethyleneimine (PEI) and mussel-inspired polydopamine (PDA), which has critical significance for PPS membrane with excellent separation performance and service durability. The modified membrane exhibits the better acid-base resistance property, due to the cross-linking reaction between catechol and amino. The continuous filtration experiment of methyl blue (MLB) and Rhodamine B (RhB) at 180 min shows that PDA/PEI modified membrane has the higher dye rejection (> 99.0%) than unmodified membrane because the modified membrane prevents dye molecules from interacting with the sulfur atom in the microporous surface of PPS membrane. After three sequential cycles, the modified membranes still exhibit the high rejection for RhB and good flux recovery ratio (> 95%), indicating that the modified membrane has higher anti-fouling property. Most importantly, the modified membrane also exhibits the high rejection of MLB in organic solution filtration process, indicating the modified membrane has good solvent resistance. The high rejection performance of modified PPS membrane is mainly due to the synergistic effect of Donnan exclusion, inter-molecular reaction and size sieving. Therefore, the PDA/PEI modified PPS membrane is not only a new candidate membrane for dye rejection, but also it is expected to be a good organic solvent resistant membrane which can be used under some harsh environmental conditions.