Membrane Filtration with Liquids: A Global Approach with Prior Successes, New Developments and Unresolved Challenges

Abstract

After 70 years, modern pressure‐driven polymer membrane processes with liquids are mature and accepted in many industries due to their good performance, ease of scale‐up, low energy consumption, modular compact construction, and low operating costs compared with thermal systems. Successful isothermal operation of synthetic membranes with liquids requires consideration of three critical aspects or “legs” in order of relevance: selectivity, capacity (i.e. permeation flow rate per unit area) and transport of mass and momentum comprising concentration polarization (CP) and fouling (F). Major challenges remain with respect to increasing selectivity and controlling mass transport in, to and away from membranes. Thus, prediction and control of membrane morphology and a deep understanding of the mechanism of dissolved and suspended solute transport near and in the membrane (i.e. diffusional and convective mass transport) is essential. Here, we focus on materials development to address the relatively poor selectivity of liquid membrane filtration with polymers and discuss the critical aspects of transport limitations. Machine learning could help optimize membrane structure design and transport conditions for improved membrane filtration performance.

“Linking microstructure of membranes and performance”

“…The drive to synthesize microporous polymer materials that preform more efficiently than those currently formed by phase inversion is being pursued by material chemists and chemical engineers [5]. With respect to polymer membranes, supposed reasons for their poor selectivity are their wide pore size distribution (often log-normal) [28], polymer and pore flexibility [29], and densification due to large free-volume loss also called ageing [30,31].…”

“…To address these limitations, current research includes the development of homogenous zeolites (aluminosilicate) [32], the formation of composite mixed matrix membranes comprising zeolites [33], MOFs [34] or polymers of intrinsic microporosity within polymer [35,36], and block co-polymer isoporous membranes [37], and cross-linked polymer membranes with post pyrolysis into carbon membranes [38]. Their advantages and limitations are reviewed by Belfort [5]. Most of these approaches, including the phase inversion process, begin with membrane synthesis followed by performance determination and iteration of syntheses to improve performance.…”

“…Porous polymer materials are traditionally synthesized through empirical optimization of a phase inversion process [1][2][3]. Pore formation occurs when a polymer solution undergoes a precipitation process involving temporal and local fluctuations in conditions that lead to a distribution of morphologies and the resultant PSD, in combination with surface chemistry controls the efficiency, selectivity, and capacity for membrane filtration and chromatography [4,5]. In the current state-of-the-art, a desired PSD is targeted through qualitative correlations of parameters in a ternary phase diagram with the process parameters of a membrane production line [6,7].…”

Application of Zwitterions in Forward Osmosis: A Short Review

“…With the exponential economic development and population growth, water resource management is important [ 1 , 2 ]. Membrane technology is an essential technique for industrial application in water treatment since the appearance of Loeb-Sourirajan membranes on the market in 1961 [ 3 , 4 ]. This is due to the great advantages of membrane technology such as continuous separation processes, low energy consumption, small footprint, ease of scale-up, and so on [ 5 ].…”

Recent Advances in Applications of Carbon Nanotubes for Desalination: A Review

“…Efficient and sustainable desalination technologies have developed under the pressure of water scarcity [1,2]. In particular, the interest in membrane-based methods among researchers and policymakers is increasing due to their superior and distinct advantages, such as high water quality with easy maintenance [3], compact modular construction [4], low chemical sludge effluent [5] and excellent separation efficiency [6]. According to the membrane process, membranes can be generally divided into different categories such as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), pervaporation and membrane distillation [7].…”