Abstract
In this work, novel polysulphone (PS) porous membranes for water desalination, incorporated with commercial and produced carbon nanotubes (CNT), were fabricated and analyzed. It was demonstrated that changing the main characteristics of CNT (e.g., loading in the dope solutions, aspect ratio, and functionality) significantly affected the membrane properties and performance including porosity, water flux, and mechanical and surface properties. The water flux of the fabricated membranes increased considerably (up to 20 times) along with the increase in CNT loading. Conversely, yield stress and Young’s modulus of the membranes dropped with the increase in the CNT loading mainly due to porosity increase. It was shown that the elongation at fracture for PS/0.25 wt. % CNT membrane was much higher than for pristine PS membrane due to enhanced compatibility of commercial CNTs with PS matrix. More pronounced effect on membrane’s mechanical properties was observed due to compatibility of CNTs with PS matrix when compared to other factors (i.e., changes in the CNT aspect ratio). The water contact angle for PS membranes incorporated with commercial CNT sharply decreased from 73° to 53° (membrane hydrophilization) for membranes with 0.1 and 1.0 wt. % of CNTs, while for the same loading of produced CNTs the water contact angles for the membrane samples increased from 66° to 72°. The obtained results show that complex interplay of various factors such as: loading of CNT in the dope solutions, aspect ratio, and functionality of CNT. These features can be used to engineer membranes with desired properties and performance.
Highlights
Global fresh water scarcity and pollution is becoming one of the most critical issues due to rapid economic development and population growth
Novel PS/carbon nanotubes (CNT) nanocomposite membranes incroporated with CCNTs or PCNTs were prepared using a phase inversion method
The results indicated that the incorporation of CNTs into the polymer matrix significantly enhances the performance of the fabricated nanocomposite membranes and must be controlled carefully to achieve the optimum results
Summary
Global fresh water scarcity and pollution is becoming one of the most critical issues due to rapid economic development and population growth. Membranes 2018, 8, 106 performance is of vital significance for practical applications of membrane separation processes for desalination and wastewater treatment [3,4] Such novel membranes must be engineered to deliver the specific water treatment needs by altering their physicochemical and structural properties, such as: porosity, hydrophilicity, chemical, mechanical, and thermal properties in addition to the incorporation of some other important features such as: adsorption, conductive or antibacterial capabilities [5]. In addition to high selectivity and permeate flux, water treatment membranes for industrial processes require good mechanical and thermal properties, stability, and durability. In pressure-driven membrane processes, the mechanical properties of the polymeric membranes are crucial as at high operating pressure, which, for example for RO may reach up to 50–60 bars, the membranes undergo physical compaction which results in an irreversible drop in the permeate water flux. Polymeric membranes characterized with low tensile strength values are vulnerable to failure due to operational stresses such as the high operating pressures [6,7,8]
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