Preparation, characterization and acid/alkali stabilities of aromatic polyesteramide-based composite membranes for water desalination

A novel aromatic polyesteramide-based membrane with high free volume for water desalination was prepared by adding a rigid cardo-contorted biphenol monomer to the aqueous phase solution of m-phenylenediamine (MPD) and then carrying out the interfacial polymerization. Compared with the polyamide (PA) membrane, the polyesteramide membrane with high free volume and ultrathin separating layer exhibited 250% increase in flux and 1.2% loss in salt rejection. Moreover, acid and alkali stabilities of polyesteramide membranes were studied by immersing the polyesteramide membranes into acid, aid/ethyl alcohol (EA), alkali and alkali/EA aqueous solutions. After acid/alkali treatments, the surface contact angles of acid/alkali-treated PA/9,9-bis(4-hydroxyphenyl)fluorine (PA/BHPF) membranes were much smaller than the pristine PA/BHPF membrane. With EA, both the acid/EA-treated and alkali/EA-treated polyesteramide membranes exhibited a significant increase in water flux; moreover, the acid/EA-treated membranes showed a simultaneous increase in water flux and salt rejection within   a   treatment   time of 24 h, due to the increase in hydrophilicity and the partial dissolution of small polymer   fragments on membrane surface.