Fabrication of trimethylphosphine-functionalized anion exchange membranes for desalination application via electrodialysis process

The design of conductive, improved durable and selective anion exchange membranes (AEMs) for desalination application via electrodialysis (ED) process is critical for a more sustainable future. This work reports the design of a series of homogeneous trimethylphosphine (TMP)-functionalized anion exchange membranes (AEMs) for desalination application via electrodialysis (ED) process. Physico-chemical characterization and electrochemical performance of the trimethylphosphine-functionalized anion exchange membranes was conducted and the activity found to be tuned by varying the quantity of trimethylphosphine into the membrane architecture. For anion exchange membranes M1 to M4, the ion exchange capacity (IEC) was increased from 1.35 to 2.16 mmol/g, water uptake (W_R) from 4.30 to 17.72%, linear expansion ratio (LER) from 3.70 to 12.50% with enhancing the quantity of trimethylphosphine into the polymer architecture. The ionic resistance decreased from 15.14 to 2.61 Ω cm² with increasing quantities of trimethylphosphine whereas transport number increased from 0.98 to 0.99. The performance of synthesized trimethylphosphine-functionalized anion exchange membranes in desalination of NaCl was evaluated via electrodialysis process (flux of 3.42 mol/m². h and current efficiency of 64.30%). Results showed that the prepared trimethylphosphine-functionalized membrane (optimum M4) possess improved desalination performance as compared to commercial membrane Neosepta AMX under identical experimental conditions.

Membrane-Based Electrolysis for Hydrogen Production: A Review

Hydrogen is a zero-carbon footprint energy source with high energy density that could be the basis of future energy systems. Membrane-based water electrolysis is one means by which to produce high-purity and sustainable hydrogen. It is important that the scientific community focus on developing electrolytic hydrogen systems which match available energy sources. In this review, various types of water splitting technologies, and membrane selection for electrolyzers, are discussed. We highlight the basic principles, recent studies, and achievements in membrane-based electrolysis for hydrogen production. Previously, the Nafion™ membrane was the gold standard for PEM electrolyzers, but today, cheaper and more effective membranes are favored. In this paper, CuCl–HCl electrolysis and its operating parameters are summarized. Additionally, a summary is presented of hydrogen production by water splitting, including a discussion of the advantages, disadvantages, and efficiencies of the relevant technologies. Nonetheless, the development of cost-effective and efficient hydrogen production technologies requires a significant amount of study, especially in terms of optimizing the operation parameters affecting the hydrogen output. Therefore, herein we address the challenges, prospects, and future trends in this field of research, and make critical suggestions regarding the implementation of comprehensive membrane-based electrolytic systems.

Experimental Evaluation of Anion Exchange Membranes for the Desalination of (Waste) Water Produced after Polymer-Flooding

Electrodialysis (ED) has been recently proposed to desalinate polymer-flooding produced water (PFPW), a byproduct stream from the oil and gas industry rich in charged polymers. However, process performance is limited by fouling occurring on the ion-exchange membranes, particularly on the anionic ones (AEMs). Thus, this study aimed to correlate the properties of different AEMs with their performance while desalinating PFPW, ultimately evaluating their significance when fouling is to be minimized and operation improved. Six stacks containing different homogeneous and commercially available AEMs were employed to desalinate synthetic PFPW during 8-days ED experiments operated in reversal mode. AEMs recovered from the stacks were analyzed in terms of water uptake, ion-exchange capacity, permselectivity, and area resistance, and compared with virgin AEMs. Relatively small changes were measured for most of the parameters evaluated. For most AEMs, the water uptake and resistance increased, while the ion-exchange capacity (IEC) and permselectivity decreased during operation. Ultimately, AEMs with high area resistance were linked to the fast development of limiting current conditions in the stack, so this property turned out to be the most relevant when desalinating PFPW.

Electrodialytic Desalination of Tobacco Sheet Extract: Membrane Fouling Mechanism and Mitigation Strategies

In the papermaking industry (reconstituted tobacco), a large number of tobacco stems, dust, and fines are discharged in the wastewater. This high salinity wastewater rich in ionic constituents and nicotine is difficult to be degraded by conventional biological treatment and is a serious threat that needs to be overcome. Electrodialysis (ED) has proved a feasible technique to remove the inorganic components in the papermaking wastewater. However, the fouling in ion exchange membranes causes deterioration of membranes, which causes a decrease in the flux and an increase in the electrical resistance of the membranes. In this study, the fouling potential of the membranes was analyzed by comparing the properties of the pristine and fouled ion exchange membranes. The physical and chemical properties of the ion exchange membranes were investigated in terms of electrical resistance, water content, and ion exchange capacity, as well as studied by infrared spectroscopy (IR) spectra, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analyses. The results indicated that the membrane fouling is caused by two different mechanisms. For the anion exchange membranes, the fouling is mainly caused by the charged organic anions. For the cation exchange membrane, the fouling is caused by minerals such as Ca²⁺ and Mg²⁺. These metal ions reacted with OH⁻ ions generated by water dissociation and precipitated on the membrane surface. The chemical cleaning with alkaline and acid could mitigate the fouling potential of the ion exchange membranes.

Custom-Made Ion Exchange Membranes at Laboratory Scale for Reverse Electrodialysis

Salinity gradient power is a renewable, non-intermittent, and neutral carbon energy source. Reverse electrodialysis is one of the most efficient and mature techniques that can harvest this energy from natural estuaries produced by the mixture of seawater and river water. For this, the development of cheap and suitable ion-exchange membranes is crucial for a harvest profitability energy from salinity gradients. In this work, both anion-exchange membrane and cation-exchange membrane based on poly(epichlorohydrin) and polyvinyl chloride, respectively, were synthesized at a laboratory scale (255 c m 2) by way of a solvent evaporation technique. Anion-exchange membrane was surface modified with poly(ethylenimine) and glutaraldehyde, while cellulose acetate was used for the cation exchange membrane structural modification. Modified cation-exchange membrane showed an increase in surface hydrophilicity, ion transportation and permselectivity. Structural modification on the cation-exchange membrane was evidenced by scanning electron microscopy. For the modified anion exchange membrane, a decrease in swelling degree and an increase in both the ion exchange capacity and the fixed charge density suggests an improved performance over the unmodified membrane. Finally, the results obtained in both modified membranes suggest that an enhanced performance in blue energy generation can be expected from these membranes using the reverse electrodialysis technique.

Modified polyether-sulfone membrane: a mini review

Polyethersulfone has been widely used as a promising material in medical applications and waste-treatment membranes since it provides excellent mechanical and thermal properties. Hydrophobicity of polyethersulfone is considered one main disadvantage of using this material because hydrophobic surface causes biofouling effects to the membrane which is always thought to be a serious limitation to the use of polyethersulfone in membrane technology. Chemical modification to the material is a promising solution to this problem. More specifically surface modification is an excellent technique to introduce hydrophilic properties and functional groups to the polyethersulfone membrane surface. This review covers chemical modifications of the polyethersulfone and covers different methods used to enhance the hydrophilicity of polyethersulfone membrane. In particular, the addition of amino functional groups to polyethersulfone is used as a fundamental method either to introduce hydrophilic properties or introduce nanomaterials to the surface of polyethersulfone membrane. This work reviews also previous research reports explored the use of amino functionalized polyethersulfone with different nanomaterials to induce biological activity and reduce fouling effects of the fabricated membrane.

Proton Conduction in Sulfonated Organic-Inorganic Hybrid Monoliths with Hierarchical Pore Structure

Porous organic-inorganic hybrid monoliths with hierarchical porosity exhibiting macro- and mesopores are prepared via sol-gel process under variation of the mesopore size. Organic moieties in the pore walls are incorporated by substituting up to 10% of the silicon precursor tetramethylorthosilicate with bisilylated benzene molecules. After functionalization with sulfonic acid groups, the resulting sulfonated hybrid monoliths featuring a bimodal pore structure are investigated regarding proton conduction depending on temperature and relative humidity. The hierarchical pore system and controlled mesopore design turn out to be crucial for sulfonation and proton conduction. These sulfonated hybrid hierarchical monoliths containing only 10% organic precursor exhibit higher proton conduction at different relative humidities than sulfonated periodic mesoporous organosilica made of 100% bisilylated precursors exhibiting solely mesopores, even with a lower concentration of sulfonic acid groups.

Effects of monovalent ions on membrane potential and permselectivity: evaluation of fixed charge density of polymer based zirconium aluminophosphate composite membrane

The composite of poly(vinyl chloride) (PVC) with zirconium aluminophosphate (ZrAlP) employed as additive was prepared by sol–gel method.

Preparation of graphene oxide nano-composite ion-exchange membranes for desalination application

Different membrane properties by inclusion of graphene oxide content.

Distribution of functional groups in periodic mesoporous organosilica materials studied by small-angle neutron scattering with in situ adsorption of nitrogen

Periodic mesoporous materials of the type (R'O)(3)Si-R-Si(OR')(3) with benzene as an organic bridge and a crystal-like periodicity within the pore walls were functionalized with SO(3)H or SO(3) (-) groups and investigated by small-angle neutron scattering (SANS) with in situ nitrogen adsorption at 77 K. If N(2) is adsorbed in the pores the SANS measurements show a complete matching of all of the diffraction signals that are caused by the long-range ordering of the mesopores in the benzene-PMO, due to the fact that the benzene-PMO walls possess a neutron scattering length density (SLD) similar to that of nitrogen in the condensed state. However, signals at higher q-values (>1 1/Å) are not affected with respect to their SANS intensity, even after complete pore filling, confirming the assumption of a crystal-like periodicity within the PMO material walls due to π-π interactions between the organic bridges. The SLD of pristine benzene-PMO was altered by functionalizing the surface with different amounts of SO(3)H-groups, using the grafting method. For a low degree of functionalization (0.81 mmol SO(3)H·g(-1)) and/or an inhomogeneous distribution of the SO(3)H-groups, the SLD changes only negligibly, and thus, complete contrast matching is still found. However, for higher amounts of SO(3)H-groups (1.65 mmol SO(3)H·g(-1)) being present in the mesopores, complete matching of the neutron diffraction signals is no longer observed proving that homogeneously distributed SO(3)H-groups on the inner pore walls of the benzene-PMO alter the SLD in a way that it no longer fits to the SLD of the condensed N(2).