Permeation Of Salts Research Articles

Residual Stress Mitigation in Perovskite Solar Cells via Butterfly-Inspired Hierarchical PbI2 Scaffold.

Residual stress in metal halide perovskite films intimately affects the photovoltaic figure of merit and longevity of perovskite solar cells. A delicate management of the crystallization kinetics is critical to the preparation of high-quality perovskite films. Only very limited methods, however, are available to regulate the residual stress of a perovskite film in a controllable manner, particularly for a perovskite film fabricated by a two-step method. Here, we demonstrate the construction of a hierarchical PbI2 scaffold inspired by Archaeoprepona demophon butterfly by combining an interlayer guided growth of porous structure and nanoimprinting. The hierarchically structured PbI2 that emulates the physical structure of the butterfly wing scale permits unimpeded permeation of organic amine salts and sufficient space for volume expansion during the crystallization process, accompanied by preferential perovskite growth of a defectless (001) crystal plane. The optimized perovskite film outperforms the control with reduced residual stress and defect density. Consequently, perovskite solar cells with a respectable power conversion efficiency reaching 23.4% (certified 23%) and an impressive open-circuit voltage of 1.184 V can be achieved. The target device can maintain 80% of initial efficiency after maximum power point tracking under illumination for 700 h. This work expands the range of engineering toward PbI2 by exploring a simultaneously tailored morphology and crystallinity and highlights the significance of a hierarchical PbI2 scaffold as an alternative choice to mitigate residual stress in a two-step processed perovskite active layer and boost the longevity of perovskite solar cells.

Bidirectional Modification of Buried Interface Reduces Energy Loss for Planar Perovskite Solar Cells with Efficiency >23%

Planar n–i–p perovskite solar cells (PSCs) based on a SnO2 electron transport layer dominate the certified high‐efficiency devices. However, the defects located at the SnO2/perovskite interface (i.e., buried interface) or inside the perovskite films impede the further improvement of power conversion efficiency (PCE). Herein, nickel acetate (NiAc2) is introduced on buried interface as a bidirectional modifier to improve electron extraction of SnO2 and the crystal growth of perovskite for the first time. First, NiAc2 is chemically anchored on SnO2 to passivate oxygen vacancies, increase conductivity, and optimize the energy level alignment of the buried interface. Second, the porous morphology of PbI2 film deposited on NiAc2‐modified SnO2 endows more sufficient permeation and reaction of organic amine salts (formamidinium iodide [FAI] and methylammonium iodide [MAI]), forming high‐quality perovskite film with reduced PbI2 residues. Meanwhile, NiI2 and MAAc/FAAc may be produced via in situ reaction between NiAc2 and organic amine salts, which serve as interface modifier and crystallization regulator to further reduce defects located at the buried interface or inside the perovskite film, respectively. Consequently, an improved PCE of 23.02% for SnO2‐based PSCs with an ultrahigh open‐circuit voltage of 1.17 V is obtained. In addition, long‐term storage and light stability of the optimized PSCs are improved.

Impact of Cation–Ligand Interactions on the Permselectivity of Ligand-Functionalized Polymer Membranes in Single and Mixed Salt Systems

We conduct molecular dynamics simulations to study the effects of cation–ligand interactions on salt permeation in ligand-functionalized polymer membranes. Our results indicate that salt partitioning into the membrane increases while the salt diffusivity decreases with enhancement in the cation–ligand interaction strength. Moreover, the increase in partitioning dominates the decline in salt diffusivity, leading to a net enhancement in salt permeation at higher cation–ligand interaction strengths. Equimolar binary mixed salt systems (having a common anion) generally exhibit much more selective partitioning of salts into the membrane as compared to their single salt counterparts. However, single salt systems exhibit much higher ratio of salt diffusivities than their mixed salt analogues. The permselectivity data closely resemble the trends in selective partitioning for both single and mixed salt systems, indicating that salt diffusivity selectivity plays a weaker role than salt partitioning selectivity in dictating the selective permeation of salts across the membrane.

Transdermal permeation of inorganic cerium salts in intact human skin

The stratum corneum protects the body against external agents, such as metals, chemicals, and toxics. Although it is considered poorly permeable to them, comprising the major barrier to the permeation of such substances, it may become a relevant gate of entry for such molecules. Cerium (Ce) is a lanthanide that is widely used in catalytic, energy, biological and medicinal applications, owing to its intrinsic structural and unique redox properties. Cerium salts used to produce cerium oxide (CeO2) nanostructures can potentially come into contact with the skin and be absorbed following dermal exposure. The objective of this study was to investigate the percutaneous absorption of three inorganic Ce salts: cerium (III) chloride (CeCl3); cerium (III) nitrate (Ce(NO3)3) and ammonium cerium (IV) nitrate (Ce(NH4)2(NO3)6), which are commonly adopted for the synthesis of CeO2 using in vitro - ex vivo technique in Franz diffusion cells. The present work shows that Ce salts cannot permeate intact human skin, but they can penetrate significantly in the epidermis (up to 0.29 μg/cm2) and, to a lesser extent in dermis (up to 0.11 μg/cm2). Further studies are required to evaluate the potential effects of long-term exposure to Ce.

Skin permeation of nickel, cobalt and chromium salts in ex vivo human skin, visualized using mass spectrometry imaging

Skin permeation and distribution of three of the most common skin sensitizers was investigated using a previously developed animal-free exposure method combined with imaging mass spectrometry. Nickel, cobalt, and chromium (III) salts were dissolved in a buffer and exposed to human skin ex vivo, to be analyzed using time of flight secondary ion mass spectrometry (ToF-SIMS). Our findings demonstrate that metal haptens mainly accumulated in the stratum corneum, however all three metal sensitizers could also be detected in the epidermis. Cobalt and chromium (III) species penetrated into the epidermis to a larger extent than nickel species. The degree of penetration into the epidermis is suggested to be affected by the sensitization potency of the metal salts, as well as their speciation, i.e. the amount of the respective metal present in the solution as bioaccessible and solubilised ions. Our method provided permeation profiles in human skin for known sensitizers, on a level of detail that is not possible to achieve by other means. The findings show that the permeation profiles are different, despite these sensitizers being all metal ions and common causes of contact allergy. Studying skin uptake by only considering penetration through the skin might therefore not give accurate results.

The effects of iontophoresis and electroporation on transdermal delivery of meloxicam salts evaluated in vitro and in vivo

The aim of this study was to evaluate the transdermal delivery of two meloxicam salts, meloxicam sodium and meloxicam potassium, enhanced by iontophoresis and/or electroporation in vitro with Wistar rat dorsal skin and human epidermal membrane (HEM) as barriers and in vivo with Wistar rat as the animal model. Iontophoresis and its combination with electroporation could significantly enhance the in vitro permeation of both salts, and two protocols had the same enhancement to each salt. Furthermore, the combination protocol had more enhancement to potassium salt than sodium salt. Interspecies difference was found in some electrical protocols. Electroporation might depress the transdermal delivery of meloxicam sodium while it might enhance that of meloxicam potassium. Iontophoresis, electroporation and their combination could increase the delivery of the two salts and result in significantly higher AUC of drug concentration to time in vivo. It was concluded that the in vitro and in vivo transdermal delivery of meloxicam potassium was more facilitated by the combination protocol than meloxicam sodium.

Enhanced fractionation of dye/salt mixtures by tight ultrafiltration membranes via fast bio-inspired co-deposition for sustainable textile wastewater management

Mussel-inspired polydopamine (PDA) coating has received increasing interest in membrane modification for versatile liquid filtration applications, due to its intrinsic adhesion nature. Nevertheless, the bio-inspired PDA deposition initiated by air-oxidation is time-consuming process and generally results in an uneven and unstable coating, which compromises the membrane filtration performance. In this study, the PDA/polyethylenimine (PEI) co-deposition triggered by ammonium persulfate (APS) was conducted to fabricate the tight ultrafiltration (t-UF) membranes with 1000–5000 Da molecular weight cut-offs (MWCOs) for sustainable treatment of highly-saline textile wastewater. APS with strong oxidation capacity can rapidly induce the co-deposition of PDA/PEI layer onto hydrolyzed polyacrylonitrile (HPAN) substrate through the Michael addition or Schiff base reactions, simultaneously minimizing the covalent polymerization of dopamine for PDA aggregation. With 1.5-h coating, a smooth, compact and defect-free PDA/PEI layer with 1700 Da MWCO was evolved on the HPAN substrate, evincing a >98.2% retention for various reactive dyes (610–1000 Da molecular weights) with >97.0% permeation of inorganic salts. In addition, an integrated UF-diafiltration procedure was applied to fractionate the reactive blue 4 (RB4)/NaCl and RB4/Na2SO4 mixtures, enriching the RB4 dye from ca. 2.04 to 50.70 g·L−1 with ca. 99.95% desalination efficiency and ca. 99.2% dye recovery. These results demonstrate that the bio-inspired t-UF membrane through fast PDA/PEI co-deposition is of great promise to sufficiently fractionate the dyes and salts for dye desalination and recovery, realizing the sustainable management of highly-saline textile wastewater.

Tannic acid-polyethyleneimine crosslinked loose nanofiltration membrane for dye/salt mixture separation

Fractionation of dyes and salts is a great challenge in high salinity wastewater from the textile industry. In this work, a high performance loose nanofiltration membrane (LNM) was fabricated to fractionate the dyes and salts in the solution via green rapid coating (GRC) process on polyethersulfone (PES) substrate. The organic solvent-free GRC process was achieved within 10 min based on the crosslinking between polyethylenimine (PEI) and tannic acid (TA). The resultant LNM performance was optimized by altering the coating parameters including the TA concentration and the coating time. The microstructure, surface properties and dye/salt separation performance of the LNM were demonstrated by characterizations and filtration experiments, respectively. With the co-existence of dye and salt, the optimized LNM exhibited desirable permeability (40.6 LMH·bar−1) and dye rejection (99.8% for 0.1 g/L Congo Red) as well as low salt rejection (6.1% for NaCl and 2.2% for Na2SO4). Furthermore, it was observed that even under 60 g/L of salt content, the satisfying rejection of CR (99.3% in Na2SO4 and 97.6% in NaCl) and high permeation of salts (98.9% for Na2SO4 and 97.9% for NaCl) can still be maintained. Moreover, the LNM showed incredible stability during the filtration process (10 h) towards dye/salt aqueous mixture. The PEI-TA/PES LNM exhibited promising application potential in dye/salt separation.

Toward real textile wastewater treatment: Membrane fouling control and effective fractionation of dyes/inorganic salts using a hybrid electrocoagulation – Nanofiltration process

In the present study, the treatments of real textile wastewater were investigated by utilizing individual electrocoagulation (EC) and nanofiltration (NF) processes as well as their hybridization (EC-NF). EC pretreatment was performed using different electrode materials (Aluminum (Al), Iron (Fe), and Titanium (Ti)). Results displayed that EC using Al electrode was superior to the other electrodes and could achieve about 64% and 94% of chemical oxygen demand (COD) and color removal, respectively. A loose NF membrane (NP010, Microdyn Nadir) was applied for NF process, providing resource recovery (salts and water reuse) through high retention of dyes and permeation of inorganic salts (fractionation of dyes/salts mixture). At the same time, the NF membrane had great removal of color (more than 87%) and ultralow rejections of inorganic salts (less than 4%). The hybridization of EC-NF could augment each other's strengths and mitigate their individual drawbacks. The NF membrane could eliminate the strong color from left-over EC-treated solutions and enhance the overall performance. Moreover, the EC process as pretreatment could reduce membrane fouling and increase the permeate flux of NF membrane. Therefore, the hybridization of EC-NF may possess superb potential for real textile wastewater treatment and efficient fractionation of dye/inorganic salts.

Novel, one-step synthesis of zwitterionic polymer nanoparticles via distillation-precipitation polymerization and its application for dye removal membrane

In this work, poly(MBAAm-co-SBMA) zwitterionic polymer nanoparticles were synthesized in one-step via distillation-precipitation polymerization (DPP) and were characterized. [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) as monomer and N, N′-methylene bis(acrylamide) (MBAAm) as cross-linker are used for the synthesis of nanoparticles. As far as our knowledge, this is the first such report on the synthesis of poly(MBAAm-co-SBMA) nanoparticles via DPP. The newly synthesized nanoparticles were further employed for the surface modification of polysulfone (PSF) hollow fiber membranes for dye removal. The modified hollow fiber membrane exhibited the improved permeability (56 L/ m2 h bar) and dye removal (>98% of Reactive Black 5 and >80.7% of Reactive orange 16) with the high permeation of salts. Therefore, the as-prepared membrane can have potential application in textile and industrial wastewater treatment.

Tight Ultrafiltration Ceramic Membrane for Separation of Dyes and Mixed Salts (both NaCl/Na2SO4) in Textile Wastewater Treatment

Commercial nanofiltration (NF) membranes have been used to separate dyes and salts in industry; however, NF membrane’s high rejection to divalent salts (i.e., Na2SO4) leads to a reduction of salt recovery. In this study, a tight ultrafiltration (t-UF) ceramic membrane (MWCO 8800 Da) is proposed to fractionate dyes and mixed salts (NaCl/Na2SO4) for textile wastewater treatment. Performance of the t-UF ceramic membrane and DK polymeric membrane (from GE) has been compared regarding to permeability, retention of reactive dyes, and permeation of salts. The t-UF ceramic membrane presents better permeability, competitive rejection of dye molecules (>98%), and reduced rejection of NaCl (<10%) and Na2SO4 (<30%) in comparison with DK membrane; the pure water permeability of t-UF membrane is at least 6 times that of DK membrane. In particular, the operation parameters (TMP, temperature, and pH) and solution environment (concentration and charges) have been intensively evaluated for dye/dual-salts separation efficie...

Enzymatic construction of antibacterial ultrathin membranes for dyes removal

This work is focused on the application of a novel antibacterial nanofiltration (NF) membrane formed by interfacial polymerization on a polyethersulfone supporting membrane for dye removal. Lysozyme, a ubiquitous and cheap enzyme with antibacterial activity was deployed as an aqueous monomer to react with 1,3,5-benzenetricarbonyl trichloride (TMC) to construct separation membranes. The formation of an ultrathin lysozyme-polymer active layer was verified by ATR-FTIR and FESEM. The degree of crosslinking, controlled by the concentration of lysozyme and TMC, had a significant influence on the physicochemical properties of the resultant membrane, as well as its separation performance. The optimum membranes show a high water flux (58.04Lm−2h−1), distinguished rejection for low molecular weight reactive dyes (600–800Da, >98.0%) and a high permeation of salts (>95%). Furthermore, the membranes with higher lysozyme concentration exhibited a sufficient antibacterial activity (81.9%) for E. coli bacteria. This facile strategy of enzyme immobilization not only allows for an in-situ preparation of enzyme-polymer membranes, but also maintains the native enzyme activity despite the high degree of covalent bonding between proteins. The resultant lysozyme membranes prove their potential in dyes removal, while also corroborating the value of interfacial polymerization in the field of enzyme immobilization and protein-polymer film construction.

High flux electroneutral loose nanofiltration membranes based on rapid deposition of polydopamine/polyethyleneimine

Tailor-made electroneutral loose nanofiltration membranes for fractionation of the dye/salt mixtures.

The application of polypropylene membranes for production of fresh water from brines by membrane distillation

Scaling and wettability of hydrophobic membranes were studied during the membrane distillation applied for the production of fresh water from the concentrated salt solutions. The studies were performed with the use of membrane modules in which the capillary membranes from polypropylene were assembled. A saline ground water containing several sparingly soluble salts was used as a feeding solution. The presence of such compounds caused an intensive surface and internal scaling. Due to the scaling, a partial wetting of the membrane walls and the permeation of salts into distillate were observed. These phenomena were eliminated for the membranes with thicker walls when the amount of deposit was limited by a periodic rinsing of the module with water. During this study, the feed was concentrated up to the supersaturation state, which caused a salt crystallization on the membrane surface, and as a consequence, the permeate flux was reduced to zero. In this case, the internal scaling can be limited using the capillary membranes with a net covering their surface.

The influence of pH on thein vitropermeation of rhodium through human skin

Workers in precious metals refineries are at risk of exposure to salt compounds of the platinum group metals through inhalation, as well as through the skin. Rhodium salt permeation through the skin has previously been proven using rhodium trichloride (RhCl3) dissolved in synthetic sweat at a pH of 6.5. However, the skin surface pH of refinery workers may be lower than 6.5. The aim of this study was to investigate the influence of pH 6.5 and 4.5 on the in vitro permeation of rhodium through intact Caucasian skin using Franz diffusion cells. A concentration of 0.3 mg mL-1 rhodium was used and analyses were performed using inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry. Results indicated a cumulative increase in permeation over 24 h. Rhodium permeation after 12 h was significantly greater at pH 4.5 (1.56 ± 0.24 ng cm-2) than at 6.5 (0.85 ± 0.13 ng cm-2; p = 0.02). At both pH levels, there was a highly significant difference ( p < 0.01) between the mass of rhodium remaining in the skin (1428.68 ± 224.67 ng cm-2 at pH 4.5 and 1029.90 ± 115.96 ng cm-2 at pH 6.5) and the mass that diffused through (0.88 ± 0.17 ng cm-2 at pH 4.5 and 0.62 ± 0.10 ng cm-2 at pH 6.5). From these findings, it is evident that an acidic working environment or low skin surface pH may enhance permeation of rhodium salts, contributing to sensitization and adverse health effects.

Nanofiltration Enrichment of Milk Oligosaccharides (MOS) in Relation to Process Parameters

Bioactive milk oligosaccharide concentrates are not yet available as functional food ingredients. The aim of the present study was to develop an optimized nanofiltration process for the enrichment of milk oligosaccharides by achieving a better permeation of milk salts and residual sugars during nanofiltration in an acidic (pH 5) or neutral (pH 7) environment. A bovine retentate produced by nanofiltration with a 100-fold increase in the milk oligosaccharide content in relation to total sugar content was applied. In addition, the process should be suitable for the enrichment of milk oligosaccharides in caprine milk. Milk oligosaccharides were identified by high performance anion exchange chromatography (HPAEC). Generally, a greater enrichment of milk oligosaccharides in the final nanofiltration retentate (14 % milk oligosaccharides by dry mass, 4-fold higher than in the first nanofiltration retentate, 140-fold higher than in the raw material) and a better separation of salts and residual sugars were achieved in bovine milk by nanofiltration at pH 5. The high milk oligosaccharide content in relation to the total sugar content in the final nanofiltration retentate (92 %, 10-fold higher than in the first nanofiltration retentate, 900-fold higher than in the starting sample) indicated a nearly complete permeation of monosaccharides and disaccharides. Nanofiltration of caprine milk resulted in a 31-fold higher milk oligosaccharide content in relation to total sugar content than in the starting sample. In the present work, the influence of the pH on the degree of enrichment of milk oligosaccharides by nanofiltration was evaluated for the first time.

Castable cements to prevent corrosion of metals in molten salts

Castable cements on metals form a protective barrier that is able to prevent permeation of molten salts towards metallic surfaces. Silica-based castable cements are capable of protecting containment metallic alloys from the corrosive attack of molten chlorides at temperatures as high as 650°C. Boron nitride (BN) blocking the pores in the cured cement prevents permeation of the molten chloride towards the metal surface. The cements tested are not chemically stable in molten carbonates, because the bonding components dissolved into molten carbonates salt. The corrosion rate is 7.72±0.32mm/year for bare stainless steel 347 in molten eutectic NaCl – 65.58wt% LiCl at 650°C, which is the baseline used for determining how well the cement protects the metallic surfaces from corrosion. In particular the metal fully encapsulated with Aremco 645-N with pores filled with boron nitride immersed in molten eutectic NaCl – 65.58wt% LiCl at 650°C shows a corrosion rate of 9E-04mm/year. The present study gives initial corrosion rates. Long-term tests are required to determine if Aremco 645-N with BN coating on metal has long term chemical stability for blocking salt permeation through coating pores.

Fabrication of asymmetrical diffusion dialysis membranes for rapid acid recovery with high purity

Anion exchange membranes with fast acid permeation and high retention of salts have been fabricated to increase the process efficiency of acid recovery from various industrial processes via diffusion dialysis, thereby greatly reducing their energy consumption and environmental impact.

Sealing nuclear graphite with pyrolytic carbon

Pyrolytic carbon (PyC) coatings were deposited on IG-110 nuclear graphite by thermal decomposition of methane at ∼1830°C. The PyC coatings are anisotropic and airtight enough to protect IG-110 nuclear graphite against the permeation of molten fluoride salts and the diffusion of gases. The investigations indicate that the sealing nuclear graphite with PyC coating is a promising method for its application in Molten Salt Reactor (MSR).

NF in organic solvent/water mixtures: Role of preferential solvation

In comparison to well-established aqueous processes, non-aqueous processes are characterized by the increase in the number of solute–solvent–membrane interactions, which play a determining role in the understanding of solvent flux and solute rejection. Straight extension of separation mechanisms, typical of aqueous environments, to non-aqueous systems is complex, due to the significant differences in the structures and properties of the solvents. In such complex systems, competition between solute–membrane and solvent–membrane affinities may become critical. The aim of this work is to study the effect of the solute–solvent competition, in terms of relative affinity with the membrane, on the nanofiltration performance in Organic Solvent Nanofiltration. Permeation of single salts and acids (NaCl, KCl, LiCl, NaI, NaF, HCl and trifluoroacetic acid, TFA-H) in water and in organic/water mixtures through hydrophilic ceramic membranes (TiO2/Al2O3) was investigated. The effect of charge was found to affect the ion retention in water, while it was found to be less significant in the presence of organic solvents. Competition between solute and solvent in terms of preferential solvation was found to affect nanofiltration and ultrafiltration of the charged solutes. The effects of pore dimension, nature of the organic solvent and nature of anion/cation for different salts and acids are presented and discussed. Afterwards, rejections of one small organic molecule, Npys, and one model peptide, PEP1, through the same hydrophilic ceramic membranes, were studied as a function of solvent composition (%v ACN/water) and ion content (Na+, H+, Cl−, and TFA−). The roles of preferential solvation and association of chaotropic/kosmotropic ions are introduced to explain the salt effects on the rejection of the organic solutes.