Abstract
High-performance Mixed-Matrix Membranes (MMMs) comprising of two kinds of porous fillers UiO-66 and Zeolite 4Aand their combination were fabricated with polysulfone (PSf) polymer matrix. For the very first time, UiO-66 and Zeolite 4A were jointly used as nanofillers in MMMs with the objective of complimenting synergistic effects. The individual and complimentary effects of nanofillers were investigated on membrane morphology and performance, pure water flux, humic acid rejection, static humic acid adsorption, and antifouling properties of membranes. Scanning Electron Microscopy (SEM) analysis of membranes confirmed that all MMMs possessed wider macrovoids with higher nanofiller loadings than neat PSf membranes and the MMMs (PSf/UiO-66 and PSf/Zeolite 4A-UiO-66) showed tendency of agglomeration with high nanofiller loadings (1 wt% and 2 wt%). All MMMs exhibited better hydrophilicity and lower static humic acid adsorption than neat PSf membranes. Pure water flux of MMMs was higher than neat PSf membranes but the tradeoff between permeability and selectivity was witnessed in the MMMs with single nanofiller. However, MMMs with combined nanofillers (PSf/Zeolite 4A-UiO-66) showed no such tradeoff, and an increase in both permeability and selectivity was achieved. All MMMs with lower nanofiller loadings (0.5 wt% and 1 wt%) showed improved flux recovery. PSf/Zeolite 4A-UiO-66 (0.5 wt%) membranes showed the superior antifouling properties without sacrificing permeability and selectivity.
Highlights
Polymeric filtration membranes have been used extensively in water treatment because of their high separation efficiency, easy automation, compactness of design, and relatively low energy consumption [1]
fouling ratio (Fr) is calculated by Equation (7) that is the degree of reversible flux loss caused by reversible fouling which can be removed by hydraulic washing
An Fourier Transform Infrared (FTIR) spectrum of UiO-66 is represented in Figure A3 (Appendix A), the band at 742 cm−1 and 1389 cm−1 are assigned as the C–H Stretch and C–O stretch respectively
Summary
Polymeric filtration membranes have been used extensively in water treatment because of their high separation efficiency, easy automation, compactness of design, and relatively low energy consumption [1]. PSf is generally associated with an undesirable hydrophobicity, which makes it prone to severe reversible and/or irreversible organic fouling resulting from the attachment of organic foulants on the membrane surface and/or their accumulation inside the membrane structure [6] Such fouling causes several inefficiencies in membrane performance such as decreased permeation flux, reduced membrane life, change in selectivity and rejection, and high operational energy and maintenance [7]. Several types of nanofillers such as titanium oxide (TiO2 ) [22], carbon nano-tubes [23,24], alumina (Al2 O3 ) [25], zeolites [26], zinc oxide (ZnO) [27,28], MOFs [29,30], silica (SiO2 ) [31,32], and graphene oxide (GO) [33] have been used to enhance the antifouling properties of filtration membranes These nanofillers have useful effects on membrane structure and characteristics. As far as we are aware, this is the very first study on the combined use of the two porous fillers (Zeolites-MOFs) in MMMs for any water purification application and especially for the enhancement of antifouling properties of membranes
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