Novel organic–inorganic hybrid composite membranes for nanofiltration of acid and alkaline media

Abstract

This study focuses on the development of novel organic-inorganic hybrid composite nanofiltration membranes based on poly(vinyl alcohol)-aminopropyl triethoxysilane (PVA-APES), which exhibit a rejection of 98.5% and a water flux of 13.5 L m À2 h À1 for a feed containing 2000 ppm Na 2 SO 4 at 2.0 MPa at best-optimized aminopropyl triethoxysilane ratio and thermal cross-linking time. No irreversible changes in membrane performance have been observed after prolonged exposure (up to several weeks) of PVA-APES-1.0 membrane to the solutions with a pH in the range of 0-14. Moreover, after exposure to different acid solutions for 150 days, the Na 2 SO 4 rejection of the composite membrane could still be maintained above 98%, and with an appropriate water flux. Notably, non-toxic solvent is used during the membrane preparation, showing enough green chemistry technology for environmental protection. A combination of high salt rejection, appropriate water flux, improved acid/alkali stability and environmentally friendly producing route indicates that these PVA-APES-xx membranes may be good candidate materials for nanofiltration in treating industrial wastewater at extreme pH values.

High-performance membranes with full pH-stability

“…Therefore, developing membranes that are stable in a wider pH-window would largely expand the potential use of NF membranes and render many large-scale industrial processes more efficient from an economic and sustainability point of view. [2][3][4][7][8][9] At low pH conditions, possible applications would include metal-ion removal from metallurgy process streams 7 or sulfate-ion removal from streams originating from the mining industry. [10][11][12] At high pH, ltration and reuse of cleaning solutions from the food and dairy industry, or the effluent treatment in pulp, paper and textile industry would benet from the use of such NF membranes.…”

“…Inopor® supplies ceramic membranes with a good stability (SiO 2 or TiO 2 , both pH 0-14). 3,7,9,17 However, all have their specic drawbacks, either due to a rather high molecular weight cutoff ($500 g mol À1 ), narrow temperature application range (10-80 C) 12 or a low permeance (<1.5 L h À1 m À2 bar À1 ). 3,18,19 All of the above drawbacks limit their commercialization and broad-scale application.…”

Proton Conducting Organic-Inorganic Composite Membranes for All-Vanadium Redox Flow Battery

“…Incorporating silica into PVA membrane via an in situ solution-gelation (sol-gel) process is a novel approach compared to the direct physical blending [ 33 ]. It prevails well-defined interconnecting conducting channels due to the uniform distribution of silica particles [ 34 ]. The compatibility of organic and inorganic phases is defined by multifold covalent bonds, hydrogen bonding and electrostatic interactions [ 35 ].…”

Treatment of Electroplating Wastewater Using NF pH-Stable Membranes: Characterization and Application

“…Most previous studies on pH-stable NF have tested the filtration performance at neutral pH after immersion of membrane coupons in acidic or alkaline solutions, assuming that changes occurring in the membrane are irreversible [3,10,12,19]. However, it has been reported that the membrane structure can change reversibly with a changing pH [34], which implies that tests at neutral pH may not be representative of the actual membrane performance during operation at extreme pH conditions.…”