Tuning the Electrochemical Properties of Novel Asymmetric Integral Sulfonated Polysulfone Cation Exchange Membranes

Abstract

In this study, novel asymmetric integral cation exchange membranes were prepared by the wet phase inversion of sulfonated polysulfone (SPSf) solutions. SPSf with different degrees of sulfonation (DS) was synthesized by variation in the amount of chlorosulfonic acid utilized as a sulfonating agent. The characterization of SPSf samples was performed using FTIR and 1H-NMR techniques. SPSf with a DS of 0.31 (0.67 meq/g corresponding ion exchange capacity) was chosen to prepare the membranes, as polymers with a higher DS resulted in poor mechanical properties and excessive swelling in water. By a systematic study, the opportunity to tune the properties of SPSf membranes by acting on the composition of the polymeric solution was demonstrated. The effect of two different phase inversion parameters, solvent type and co-solvent ratio, were investigated by morphological and electrochemical characterization. The best properties (permselectivity of 0.86 and electrical resistance of 6.3 Ω∙cm2) were obtained for the membrane prepared with 2-propanol (IPA):1-Methyl-2-pyrrolidinone (NMP) in a 20:80 ratio. This membrane was further characterized in different solution concentrations to estimate its performance in a Reverse Electrodialysis (RED) operation. Although the estimated generated power was less than that of the commercial CMX (Neosepta) membrane, used as a benchmark, the tailor-made membrane can be considered as a cost-effective alternative, as one of the main limitations to the commercialization of RED is the high membrane price.

Polysulfone with Different Degrees of Sulfonation: Simple Method with Acetyl Sulfate

“…These signals were maintained in the sulfonated polymers, the evidence that sulfonation occurred is given by the appearance of signals in the range between 3556-3421 cm -1 referring to SO2OH stretching; 1237, 1144, 1104, and 1040 cm -1 (with small variation between the PSU-S samples), referring to the S-O stretching (highlighted in Figure 3-b) through the amplification of the peaks in the region between 600 and 1500 cm -1 ). These data agree with those of Ryu et al [35], and Avci et al [14]. Dourado [24], Eroglu et al [31], Martos et al [29], and Smitha et al [33].…”

“…In these examples, to facilitate understanding of the discussion, it is considered that the substitutions occur in the priority positions (2 and 7) of the PSU, but in practice, the possibilities for insertion of the -SO3H group are much more diverse, complex, and capable of other combinations. The numbering of protons followed the model presented by Eroglu et al [31] and Avci et al [14].…”

“…The introduction of sulfonic groups has been one of the PSU functionalization tools, due to the possibility of increasing hydrophilicity and improving its permeability, porous size, and other fundamental characteristics for ion exchange membrane in electrolysis processes, electrodialysis, dialysis, fuels cells, reverse electrolysis, sensors, and catalysts for various purposes [14][15][16][17][18][19][20].…”

“…Over time, lots of reactants have been employed in PSU sulfonation, being able to highlight the sulfur trioxide-triethyl phosphate complex (SO3/TEP) [21][22][23], fuming and concentrated sulfuric acid [24], trimethylsilyl chlorosulfonate (TMSClS) [25][26][27][28][29][30][31][32] and chlorosulfonic acid (HSO3Cl) [14,19,20,[29][30][31][33][34][35][36]. These reaction conditions need more careful handling compared to the method proposed in this work.…”

The advent of thermoplasmonic membrane distillation

“…377 Ag played the dual role of: (i) thermoplasmonic effects facilitating the vaporization of water at a rate of 1.49 kg m À2 h À1 under 1 sun and (ii) a cocatalyst to facilitate charge transfer and the light absorption for improved hole-scavenging activity for the photocatalytic H 2 generation at a rate of 3260 mmol m À2 h À1 377 . An emerging trend is to exploit the electrochemical potential of the brines to produce renewable blue energy (Salinity Gradient Power) via Reverse Electrodialysis (RED), an electromembrane-based process that harvests the Gibbs free energy of mixing of solutions with different salinity; 378 feeding the hypersaline retentate from the photothermal SGMD unit to a RED stack enabled the recovery of 10% of the energy not used for water evaporation, thus improving the overall efficiency of the integrated system. 280 Biofouling control is essential to extend the shelf-life of the membrane, to reduce the operation and maintenance cost, to sustain the long-term performance of the membrane process, and to ensure a stable quality of produced water.…”