Fabrication and characterization of polyethersulfone membranes functionalized with zinc phthalocyanines embedding different substitute groups

In this study, a novel polyethersulphone (PES) composite membrane incorporated with two different zinc phthalocyanines (ZnPc), tetra-iodo and octa(2,6-diphenylphenoxy), was fabricated through the phase inversion approach. Three different concentrations of zinc phthalocyanines (0.5, 1.0, and 2.0 wt.%) were blended into the PES membrane. The morphology and performance of the fabricated composite membranes were systematically studied by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) mapping, atomic force microscopy (AFM), porosity, water contact angle, antifouling, and rejection measurements. Hydrophobicity of the pristine membrane decreased from 79.67 degrees to 77.03 degrees and from 79.67 degrees to 67.57 degrees after blending of 2.0 wt.% tetra-iodo ZnPc (TI-ZnPc) and octa(2,6-diphenylphenoxy) ZnPc (DP-ZnPc), respectively. Furthermore, the porosity and mean pore radius decreased due to the introducing of ZnPc. Porosity of the pristine membrane decreased from 60.60 % to 44.96 % and 42.21 % after blending of TI-ZnPc and DP-ZnPc, respectively. Mean pore size of the pristine membrane decreased from 22.70 nm to 9.11 nm and 17.93 nm after blending of TIZnPc and DP-ZnPc, respectively. BSA filtration mostly affected the flux of pristine membrane and caused it to decrease from 133.5 to 87.1 L/m(2)h (relative flux reduction (RFR) of 34.7 %). RFR decreased up to 19.2 % and 17.3 % for TI-ZnPc 2.0 wt% and DP-ZnPc 2.0 wt% composite membranes. Pristine PES membrane rejected 45.8 % BSA. However, TI-ZnPc 2.0 wt% and DP-ZnPc 2.0 wt% composite membranes supplied 91.0 % and 70.6 % BSA rejections, respectively. In comparison to pristine PES membrane, the total resistance (R-t) values of the composite membranes decreased. The pristine PES membrane showed the lowest flux recovery ratio (FRR, 71.89 %) against BSA, while all-composite membranes showed promising antifouling properties. FRR increased up to 97.44 % and 89.06 % for TI-ZnPc 2.0 wt% and DP-ZnPc 2.0 wt% composite membranes, respectively. The pristine PES membrane showed the lowest FRR against activated sludge, while all composite membranes showed promising antifouling properties. Moreover, ZnPc-embedded PES composite membranes were irradiated with appropriate wavelengths of light in the presence of oxygen to generate reactive oxygen species to clean fouled membranes' surface. The results showed that photo-cleaning was very effective to recover membrane flux.

Automated summary

In this study, a novel PES composite membrane incorporated with different concentrations of zinc phthalocyanines was fabricated through phase inversion, leading to improved membrane morphology and performance. The hydrophobicity of the membrane decreased after blending ZnPc, while porosity and mean pore radius also decreased. The composite membranes showed enhanced antifouling properties and increased rejection of BSA compared to the pristine PES membrane. Photo-cleaning with appropriate light wavelengths effectively recovered membrane flux, demonstrating promising membrane cleaning capabilities.