Abstract
The pyromellitic dianhydride (PMDA) crosslinked poly(vinyl alcohol) (PVA) was coated on top of the PAN ultrafiltration membrane to form a PVA/PAN composite PV membranes for wastewater desalination. The composite membranes have high application value in industrial wastewater treatment. By varying the membrane fabrication parameters including the weight percent (wt%) of the PMDA, the crosslink temperature and duration, membrane with the best desalination performance was obtained. The composite membrane with a 2-μm-thick PVA selective layer containing 20 wt% of PMDA and being crosslinked at 100 °C for 2 h showed the highest NaCl rejection of 99.98% with a water flux of 32.26 L/(m2 h) at 70 °C using the 35,000 ppm NaCl aqueous solution as feed. FTIR spectroscopy, wide-angle X-ray diffraction, thermogravimetric analysis and scanning electron microscope have been used to characterize the structures and properties of both the crosslinked PVA dense films and PVA/PAN composite membranes. The effects of the concentrations of PMDA, the crosslinking time and temperature to the membrane water contact angle, swelling degree, salt rejection and water flux were systematically studied.
Highlights
Water shortage has become a global issue that threats our daily life (Newman 1995; Wang et al 2015)
As the pyromellitic dianhydride (PMDA) concentration increases, more –OH groups of the poly(vinyl alcohol) (PVA) molecules react with the –COOH group of the hydrolyzed PMDA crosslinked, and the peak intensity of the O–H band (3320 cm-1) gradually decreases
Peaks prove the occurrence of the crosslink reaction and the crosslinking degree increases with the concentration of PMDA
Summary
Water shortage has become a global issue that threats our daily life (Newman 1995; Wang et al 2015). Researchers start to study the feasibility of PV membranes for salty water desalination (Chaudhri et al 2015; Cho et al 2011b; Drobek et al 2012; Liang et al 2014, 2015; Wang et al 2016b; Xie et al 2011; Zwijnenberg et al 2005). The reported data demonstrate that both inorganic and polymeric PV membranes have high salt rejections but the water fluxes are relatively low (0.2–22.87 L/(m2 h)) when separating a 1 wt% NaCl solution at 63 °C (Wang et al 2016a; Xie et al 2011; Zwijnenberg et al 2005). Since PVA is soluble in water, modification methods such as crosslink have to be used to increase its stability. The PMDA crosslinked PVA polymer may have high water flux as well as good stability in water. PV desalination tests were performed at different temperatures and NaCl concentrations to evaluate the separation performances of the prepared membranes
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