Molecular Spectroscopic Characterization of Membrane Fouling: A Critical Review

Abstract

Membrane technologies have attracted growing interest in the fields of water purification and energy recovery. Membrane fouling is the bottleneck that limits the wide application of membrane-based technologies. Exploration of the fouling mechanism and the chemical composition, structure, and functions of foulants and their changes in the membrane filtration process is therefore of significant importance. Molecular spectroscopic methods are among the most efficient platform tools for characterizing membrane fouling because of their unique advantages, such as chemical identification at the molecular level, high sensitivity, and spatially temporally resolved feasibility. Here, an overview of spectroscopic and microspectroscopic approaches, including UV-vis, fluorescence, infrared, and Raman spectroscopy, for the online detection, identification, visualization, and chemical characterization of membrane fouling is provided, and their main advantages as well as limitations in membrane-fouling research are analyzed. Furthermore, future possibilities and challenges for the development of molecular spectroscopy for membrane-fouling characterization are envisaged in this critical review.

Two-electron transfer stabilized by excited-state aromatization

“…To investigate the conformational change of TMTQ by the excited-state iCT process, we measured IR spectra in the region of 1275–1575 cm −1 for C=C stretching modes 37,38 . Because the intensity of IR bands is sensitive to the change of dipole moment within the vibrational motions 15,21,39,40 , the dipole moment change triggered by the C=C stretching modes along the π-conjugation pathways allows us to estimate structural planarization (or distortion) based on the decreased (or increased) IR intensity of C=C stretching modes between the FT-IR and transient IR spectra. The FT-IR spectra showed intense bands at 1479 and 1529 cm −1 and weak bands at 1301, 1359, and 1421 cm −1 , which are well matched with the GSB signals in the transient IR spectra.…”

A review of in situ real-time monitoring techniques for membrane fouling in the biotechnology, biorefinery and food sectors

“…Furthermore, an extensive review of methods of probing solid/liquid surfaces at the molecular level has been presented by Zaera [13], and many of these methods can easily be applied to membrane technology. A paper on the use of molecular spectroscopy methods for studying membrane fouling [14] and a state-of-the-art review of methods for membrane surface characterization [15] have recently been published, both of which include aspects interesting for in situ real-time monitoring of organic membrane fouling.…”

Optimization of Operation Parameters in Ultrafiltration by Experiment Design, Mathematical Modelling and Fouling Characterization of the Membranes Used to Remove Dissolved and Colloidal Substances from a Treated Paper Mill Effluent

“…The functional groups absorb energy at specific wavelengths (spectral range 4.000-400 cm -1 ), which can be shifted in intensity or position by substituent effects from adjacent atoms . ATR-FTIR spectra are usually divided into two regions: the functional group region (4.000 -1.350 cm -1 ) and the fingerprint region (1.350 -400 cm -1 ) (Chen et al, 2018).…”

“…In literature, several researches have been applied (ATR-FTIR) to detect the presence of different bands of the fouling layer on fouled membranes such as proteins, fatty and resin acids, colloids, polysaccharides and membrane substrates Chen et al, 2018;Delaunay et al, 2008;Jensen et al, 2015;Pihlajamäki et al, 1998), besides to provide an easy and interpretable overview of fouling distribution over the virgin and fouled membrane (Chen et al, 2018). Gelaw et al 2014 Previous studies demonstrated that the peaks for the fresh PES ultrafiltration membranes were found around 1147.34 cm -1 can be assigned to S=O symmetric stretching mode in-SO 2- (Angione et al, 2015), 1240 cm −1 which arises from the asymmetric stretch of the aromatic ether (Ar-O-Ar ethers) in the polyethersulfone (Jensen et al, 2015), and 1643 cm -1 and 3400 cm -1 characteristic for the aromatic bands and aromatic double (bonded carbons), respectively.…”

“…9 -Summary comparing analytical techniques for foulant identification and characterization of membrane fouling. Addapted from(Chen et al, 2018).Beyer, F., Laurinonyte, J., Zwijnenburg, A., Stams, A.J.M., Plugge, C.M., 2017. Membrane Fouling and Chemical Cleaning in Three Full-Scale Reverse Osmosis Plants Producing Demineralized Water [WWW Document].…”