Résumé
Background Self-supporting flat-sheet polyvinylidene fluoride (PVDF) membranes comprising amphiphilic I-quartet artificial water channels (AWC) were manufactured by a combining a VIPS pretreatment with a NIPS stage. The AWCs are formed in situ by the self-assembly of Hexylureido-ethyl-imidazole (HC6) molecules present in the dope solution, upon contact with the nonsolvent water during the phase separation process. The microporous membranes were employed for membrane distillation (MD). Methods A design of experiment (DoE) was used to investigate the influence of various experimental parameters and their interactions on membrane performance, namely polymer and AWC concentrations in the dope solution, relative humidity and duration of the VIPS treatment. Pure water permeability (PWP), liquid entry pressure (LEP) and MD flux were used to characterize membrane performance. A response surface methodology (RSM) was used to evaluate the DoE results and a second order model was fitted. Based on the model predictions several multiple response-optimized (MRO) membranes were prepared. Results The performance improvement of the MRO membranes was 7.0 times for PWP (M-T4) and 3.3 times for MD flux (M-T3) over the average performance of the DoE membranes, while maintaining LEP of 1.9 bar and NaCl rejection of 99.9%. In addition, PVDF/HC6 hybrid MRO membranes improved PWP by 3.2 times and MD flux by 1.6 times over pure PVDF MRO membranes. Conclusions DoE in conjunction with RSM enabled the prediction of membrane PWP, LEP and MD flux performance by varying the levels of the experimental parameters within predefined limits. The HC6 additive improves PWP and MD flux without loss of LEP or selectivity.