Characterization of membrane–foulant interactions with novel combination of Raman spectroscopy, surface plasmon resonance and molecular dynamics simulation

Abstract

Adsorptive fouling, by phenolic compounds, is a serious issue regarding the development and use of membrane based filtration technologies for water purification and wastewater treatment. We have developed a novel, combined, protocol of Raman spectroscopy and surface plasmon resonance (SPR) experiments, along with molecular dynamics (MD) simulation, to study the interaction of vanillin, a model phenolic compound, with the polyethersulfone (PES) surface of a membrane. The adsorption of vanillin to the PES surface was found to be highly pH dependent; the source of this was determined, by MD simulation, to be the stronger interaction with the protonated form of vanillin, predominant at low pH. Vanillin interacts with the PES surface, both through entropy driven, hydrophobic, interactions and, for the case of the protonated form, H-bonding of the hydroxyl group with the sulphur oxygens of the PES molecules. In addition to general insight into the fouling process that can be used to develop new methods to inhibit adsorptive fouling, our results also elucidate the specific interaction of the PES membrane with vanillin that can be used in the development of anti-fouling coatings, based on the structure of vanillin.

Utilization of DES-Lignin as a Bio-Based Hydrophilicity Promoter in the Fabrication of Antioxidant Polyethersulfone Membranes

“…In addition, the area of C–H aromatic stretching vibration (3100–3000 cm ) and aliphatic stretching vibration (2922–2875 cm ) become more intense due the presence of DES-lignin in the structure of the modified membrane. The same behavior of interaction between a PES membrane and vanillin, as one of lignin derivatives, was also observed in our previous work [ 42 ] and in the study done by Virtanen et al, where the interactions between phenolic model compound vanillin and PES surface was comprehensively investigated [ 43 ]. They also mention that hydrogen bond formation between the hydroxyl group of this phenolic compound and ether oxygen of PES could also be established, although the hydrogen bonding with sulfur is the dominant interaction.…”

Visual tool for real-time monitoring of membrane fouling via Raman spectroscopy and process model based on principal component analysis

“…The Raman data collection process used has been described in detail in previous studies 11 , 29 . Raman spectra were recorded during cross-flow experiments using a Kaiser RXN1 spectrometer with 785 nm laser excitation and maximum power of 400 mW.…”

“…Different adsorption times (15, 30 and 195 min) were also tested. In the second experimental set 29 the concentration of vanillin (0.75 g/L) and adsorption time (120 min) were constant but the pH was varied (pH 2, 7.4 and 10). Tests were repeated three times for each conditions.…”

“…for quantification of strong acid concentration in solutions 26 , to monitor lignocellulosic bioethanol production processes 27 and for predictive modeling of cell culture growth and metabolite production 28 . Our previous studies have shown that online measurement by Raman spectroscopy can be used for rapid, direct and non-invasive detection of adsorption processes on the surface of the membrane 11 , 29 . However, in our previously published approach the chemometric analysis run was done individually for each adsorption experiment data set and scaling of the results for getting quantitative accumulation curves required ex situ calibration measurements.…”

“…Thus vanillin was used as a adsorptive model compound due to its lignin-related structure, phenolic amphipathic nature and intense Raman response of the delocalized π-electrons. Previously acquired Raman spectra and external calibration data 11 , 29 were used to build a PCA model describing a smoothly running membrane process. Validation of the method was performed through a comparison of measured values to those predicted by the model.…”