The development of chemically modified P84 Co-polyimide membranes as supported liquid membrane matrix for Cu(II) removal with prolonged stability

We have demonstrated, for the first time, P84 co-polyimide with novel chemical cross-linking modification can be effectively used as the polymeric microporous matrix for supported liquid membrane (SLM) applications. Both asymmetric and symmetric flat membranes with high tortuosity were fabricated via the phase inversion method. It is found that the symmetric membrane outperforms the asymmetric one because the former may provide (1) balanced forces exerted at two aqueous/membrane interfaces and (2) the formation of more stable stagnant layers than the latter. However, the performance of both unmodified asymmetric and symmetric flat membranes deteriorates severely after use for 20-30 h. A novel chemical modification agent, p-xylenediamine/water, was discovered and shows effectiveness to improve P84 membrane stability for SLM. The improved SLM stability is attributed to the reduced pore size and the enhanced hydrophobicity on the membrane surfaces. The newly developed chemically modified SLM has a similar lifetime compared with other SLM systems using commercial PTFE as the support matrix.