Assessment of Layer-By-Layer Modified Nanofiltration Membrane Stability in Phosphoric Acid

Abstract

Nanofiltration (NF) can enable P recovery from waste streams via retaining multivalent impurities from spent pickling acid. However, with the currently available membranes, an economically feasible process is impossible. Layer-by-layer modified NF membranes are a promising solution for the recovery of P from acidic leachate. LbL membranes show a high level of versatility in terms of fine tuning for ion retention, which is necessary to achieve sufficient phosphorus yields. However, the stability of layer-by-layer modified membranes during phosphoric acid (H3PO4) filtration needs to be further investigated. In our study, we show that a polyethersulfone hollow fiber membrane modified with four or eight bi-layers was stable during immersing and filtering of a 15% H3PO4 solution. A sulfonated polyethersulfone (sPES)-based hollow fiber LbL membrane was only stable during filtration. Thus, we show the importance of applying real process conditions to evaluate membranes. Another important aspect is the influence of the high ionic strength of the feed solution on the membrane. We show that a high ionic strength led to a decrease in Mg retention, which could be increased to 85% by adjusting the process parameters.

Advances and Applications of Hollow Fiber Nanofiltration Membranes: A Review

“…The obtained permeabilities were significantly higher than commercial benchmark membranes (e.g., A-3012 AMS membrane). Later they investigated the stability of LbL based PEM membranes when immersing or filtering 15% H 3 PO 4 solution [197]. Using PES as support layer, the membranes proved to be very stable after both immersion and filtration.…”

How Does Alkali Etching Work on the Polyamide Membrane to Obtain an m-Phenylenediamine-Based NF Membrane?

“…Multifunctional amines such as poly­(ether imide) (PEI), melamine (Mel), and ethylene diamine as water phase monomers reacted with cyanuric chloride or 1,3,5-tris­(bromomethyl)-benzene to fabricate polyamine membranes that presented better pH resistance than their polyamide equivalents. ,− Polysulfonamide membranes also showed an excellent stability in extreme acidic conditions, − and the mechanism was further researched. , Sometimes the combination of different amines such as Mel/PIP and Mel/PEI could lead to an improved stability for acidic nanofiltration under conditions of pH < 2. For example, sulfonated-melamine formaldehyde/sulfanilamide or naphthalene-1,3,6-trisulfonyl chloride was mixed with PIP to fabricate an NF membrane by IP reaction, and the resulting membrane exhibited better acid resistance because of the more stable C–N bonds in the PA network. , Polyelectrolyte multilayer membranes prepared through layer-by-layer coating also outperformed PA membranes with regard to acid stability for the nature of strong cation and anion polyelectrolytes over a wide pH range. − NF membranes with proper chemical stability for commercial applications could be obtained by coating steps. Zhang et al fabricated the NF membranes by brush-coating the substrate with poly­(vinyl alcohol) and 3-mercaptopropyltriethoxysilane aqueous solution, which retained stable Na 2 SO 4 rejection upon immersing in 15% H 2 SO 4 and 4% NaOH solutions for 30 days.…”

Development of Thin-Film Composite Membranes for Nanofiltration at Extreme pH

“… 8 − 13 However, the low stability of NF membranes remains a drawback and often hinders their application in a broader range, where the solution to be filtered can damage the membrane. 14 , 15 This is a critical issue because most of the effluents in chemical factories are often at extreme pH and highly corrosive. 16 − 20 Conventional polymer NF membranes quickly lose their performance upon contact with either acidic or alkaline solutions.…”

“…The pore size is defined so that the nonharmful monovalent salts could pass through the membranes, while micropollutants and heavy metals would be easily retained . The NF process has been successfully applied to numerous separation processes in industrial scales. − However, the low stability of NF membranes remains a drawback and often hinders their application in a broader range, where the solution to be filtered can damage the membrane. , This is a critical issue because most of the effluents in chemical factories are often at extreme pH and highly corrosive. − Conventional polymer NF membranes quickly lose their performance upon contact with either acidic or alkaline solutions . Hence, the need for developing highly robust materials for membrane fabrication is rapidly emerging, and this could be achieved by carefully engineering the chemistry of materials.…”