Mixture Of Cations Research Articles

Holistic design principles for flow batteries: Cation dependent membrane resistance and active species solubility

Cation dependent resistance of a commercial cation exchange membrane, Nafion™ 212, as well as the solubility of select active materials are investigated, demonstrating practical consequences of cation choice on redox flow battery (RFB) performance. The conductivity of alkali and methyl- or -alcohol substituted ammonium cations through pretreated Nafion™ 212 reveal that cation size is the dominant factor affecting ionic transport. Among the alkali series the resistance increases with larger ionic radii and similarly, with increasing steric bulk through substitution on ammonia. The solubility of ferrocyanide, a commonly used redox flow battery posolyte (or catholyte), as well as iron, cobalt, and chromium metal-organic compounds are determined for the same series of cations. Full cells are assembled using various cation mixtures and membrane pre-treatments to demonstrate practical effects of each variable. We highlight the need to carefully select the correct cations for efficient electrolyte design, since certain cations may lead to high conductivity but low solubility, or vice versa, and provide design principles for RFBs using Nafion™ 212.

Molecular insights into the effect of anionic-nonionic and cationic surfactant mixtures on interfacial properties of oil-water interface

The influence of surfactants is of great importance to the interfacial properties, which is related by the characteristics of molecular arrays at the interface of multicomponent and multiphase systems. Comparing with single type of surfactant, the mixtures of surfactants usually provide superior performances in improving interfacial properties of the oil-water interface in the application of enhanced oil recovery. In this study, molecular dynamics simulations were employed to explore the mechanisms and interfacial behaviors at the microscopic level of pure and binary mixture of anionic-nonionic surfactant alcohol ether sulfates (AES) and cationic surfactant dodecyltrimethylammonium chloride (DTAC) at oil-water interface. The results show that the sulfate groups of AES molecules could attract DTAC molecules in the mixed surfactants, thereby reducing the repulsion between the molecules. DTAC molecules present excellent molecular interfacial behaviors, which could improve the arrangement of AES molecules through the interactions between head groups. In addition, it is found that the number of ethylene oxide (EO) group of AES molecules has a great influence on the behaviors of interface. An increase of EO group number could cause AES molecules to exhibit varying degrees of bending. By controlling the proper number of EO group, the aggregation of surfactants could be avoided and satisfactory interfacial properties will be achieved. Moreover, it is observed that the positive charge of DTAC molecule shows a strong repulsion to salt ions, for example Ca2+ ions, thus enhancing the overall salt resistance of mixed surfactants. The molecular-level insights gained in this work could provide useful guidance for designing the surfactant formulations for tertiary/enhanced oil recovery in low-permeability unconventional reservoirs.

A New Schiff Base Organically Modified Silica Aerogel-Like Material for Metal Ion Adsorption with Ni Selectivity

Nickel has several industrial uses and is a valuable metal, making its selective separation and recycling a priority goal. A novel adsorbent, a Schiff base organically modified silica (ORMOSIL) aerogel, was prepared, for selective nickel removal from wastewater with other metal ions, by including a salen ionophore in the silica-based network. The newly developed adsorbent takes advantage of the salen’s selectivity and of the high porosity of silica aerogels. The aerogel-like adsorbent was prepared via sol-gel chemistry, using a coprecursor approach and ambient pressure drying. The inclusion of the Schiff base in the silica network was accomplished by reacting an amine-containing silica precursor with an aldehyde and confirmed by nuclear magnetic resonance (NMR) analysis. The adsorbent shrunk only 10% after evaporative drying, which resulted in a highly porous material (85% porosity, 4 cm3 g−1 specific pore volume). The low surface area of 28 m2 g-1 was due to the predominantly macroporous structure of the material (mean pore diameter of 563 nm). Adsorption isotherms and kinetic curves with single and binary mixtures of cations at room temperature were used to assess the selectivity of the adsorbent. The adsorption follows a BET (Brunauer-Emmett-Teller) trend. Due to the proximity of the oxygen and nitrogen atoms in the salen and steric hindrance from their neighboring atoms, it is likely that only the smallest hydrated cations can act as a coordination center and interact with both donor atoms. Thus, nickel was fairly removed (50 mg g-1), while other cations barely interacted with the adsorbent (cadmium adsorption maximum of 5 mg g-1). The estimated selectivity coefficient for nickel ranges from 1.8, in relation to copper, to 9.4 relatively to cadmium, which can be relevant for the separation of nickel in several industrial contexts, for instance, from electroplating sludge.

Surface Activity and Efficiency of Cat-Anionic Surfactant Mixtures.

The surface activity of surfactant mixtures is critically analyzed. Cat-anionic systems, in which two ionic species are mixed in non-stoichiometric ratios, are considered. With respect to the solution behavior, where a substantial decrease of cmc is met compared to the pure components, a moderate effect on surface tension, γ, occurs. Compared to the pure species, the decrease of surface tension for such mixtures is not significant, and no clear dependence on the mole fraction anionic/cationic is met. The surface tension is grossly constant in the whole concentration range. Conversely, the interaction parameter for surfaces, β surf (calculated by the regular solution theory), is more negative than that for micelle formation, β mic . This fact suggests that the desolvation of polar heads of the two species at interfaces is largely different. Very presumably, the underlying rationale finds origin in the sizes and solvation of both polar head groups.

UPLC-ESI-MS analysis of salts using a porous graphitic carbon column

A method for the identification and quantification of salts relevant in the analysis of explosives was developed for a porous graphitic carbon (PGC) UPLC/HPLC column combined with ESI-MS detection. The presented method covers a wide range of energetic salts and provide a valuable analytical tool for security, forensic as well as environmental monitoring. Both anionic and cationic species can be identified and quantified in a single chromatographic run. Afterward, analytes can be indubitably identified by LC-MS equipped with an atmospheric pressure ionisation (API) interface. Since the retention mechanism of PGC is due to combination of different interactions, a tunable retention can be obtained by adjustments of the composition of the mobile phase. The use of LC-MS in combination with PGC is an improved alternative to the existing analytical methods based on silica derivatised reversed phase (RP) columns. A high percentage of ammonia in the mobile phase allowed elution of the most highly retained analytes. The effects of different solvents and their combinations and mobile phase additives were evaluated. The developed method improves the energetic salts detection in terms of sensitivity and selectivity. The effectiveness of the method is demonstrated by the analysis of a reference mixture of anions and cations.

Transition kinetics of mixed lipid:photosurfactant assemblies studied by time-resolved small angle X-ray scattering

HypothesisPhotoswitchable surfactants are used in the design of many light-responsive colloids and/or self-assemblies. Photo-isomerization enables to control molecular equilibrium, and triggers transient reorganizations with possibly out-of-equilibrium intermediate states that have been overlooked. Here, we address this question by an in depth structural investigation of intermediate lipid-surfactant assemblies that occur during fast isothermal photo-triggered transition in lipid:surfactant mixtures. ExperimentsThe structural parameters of mixed assemblies of azobenzene-containing cationic surfactant (AzoTMA) and dioleoylphosphatidylcholine (DOPC) lipids were studied by light scattering and time-resolved small angle X-ray scattering. Structural and compositional information about the assemblies and unimers in bulk were determined at the photostationary states, as well as at intermediate kinetic states formed during UV or blue light illumination. FindingsDOPC:AzoTMA systems form mixed assemblies representative of phospholipid:cationic surfactant mixtures, that evolve from spheroid, to rod-like micelles, and vesicles with increasing DOPC fraction. Transient assemblies detected during the photo-triggered kinetics are similar to the ones found in stationary states. But changes of AzoTMA unimers in bulk can be considerably faster than mass reorganizations of the mixed assemblies, suggesting that out-of-equilibrium conditions are transiently reached. Mass reorganization of the surfactant-enriched assemblies is much faster than in the lipid enriched ones, providing insight into the role of lipids in a slow reorganization of the assemblies.

Understanding the physicochemical properties of Zn\u2013Fe LDH nanostructure as sorbent material for removing of anionic and cationic dyes mixture

In our work, the removal of cationic and anionic dyes from water was estimated both experimentally and computationally. We check the selectivity of the adsorbent, Zn–Fe layered double hydroxide (LDH) toward three dyes. The physical and chemical properties of the synthesis adsorbent before and after the adsorption process were investigated using X-ray photoelectron spectroscopy, energy dispersive X-ray, X-ray diffraction, FT-IR, HRTEM, and FESEM analysis, particle size, zeta potential, optical and electric properties were estimated. The effect of pH on the adsorption process was estimated. The chemical stability was investigated at pH 4. Monte Carlo simulations were achieved to understand the mechanism of the adsorption process and calculate the adsorption energies. Single dye adsorption tests revealed that Zn–Fe LDH effectively takes up anionic methyl orange (MO) more than the cationic dyes methylene blue (MB) and malachite green (MG). From MO/MB/MG mixture experiments, LDH selectively adsorbed in the following order: MO > MB > MG. The adsorption capacity of a single dye solution was 230.68, 133.29, and 57.34 mg/g for MO, MB, and MG, respectively; for the ternary solution, the adsorption capacity was 217.97, 93.122, and 49.57 mg/g for MO, MB, and MG, respectively. Zn–Fe LDH was also used as a photocatalyst, giving 92.2% and 84.7% degradation at concentrations of 10 and 20 mg/L, respectively. For visible radiation, the Zn–Fe LDH showed no activity.

Effect of methanol on surfactants and surfactant–PEO mixtures

AbstractMethanol–water system possesses unusual interactions, which may affect surfactant self‐assembly. The main objective of this study was to investigate the interactions and aggregation behavior of ionic surfactants sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) and their equimolar catanionic binary mixtures (CAM) and their ternary mixtures with poly(ethylene oxide) (PEO) in aqueous solutions containing different volume percentages of methanol. Conductometry, surface tensiometry, and dynamic light scattering were employed for this purpose. The aggregation in all the systems showed methanol‐dependent patterns. The maximum shifts observed in the critical aggregation concentrations were 5.5, 2.7, 6.3, 4.1, and 4.4 mM, respectively, for SDS, CTAB, CAM, SDS/PEO, and CTAB/PEO systems for variation in MeOH from 5% to 30% v/v. The change in dielectric of the media and chaotropic nature of methanol was responsible for alteration in self‐assembly. The nature of surfactant especially and head group hydrophobicity also played a significant role in the process. The maximum change in area per molecule (i.e., ~4 nm2) occurred for CTAB/PEO system. The aggregation was delayed in surfactant solutions; however, the presence of polymer induced aggregation due to favorable polymer–surfactant interactions involving the surfactant adsorption onto polymer chains and formation of mixed aggregates. The hydrodynamic radii for CTAB/PEO systems, which were nearly 10 times greater than those recorded for SDS/PEO, showed the transition of system to nonspherical aggregated states. In short, the presence of methanol retarded the aggregation in surfactant and surfactant–polymer systems.

Design Principles of Large Cation Incorporation in Halide Perovskites.

Perovskites have stood out as excellent photoactive materials with high efficiencies and stabilities, achieved via cation mixing techniques. Overcoming challenges to the stabilization of Perovskite solar cells calls for the development of design principles of large cation incorporation in halide perovskite to accelerate the discovery of optimal stable compositions. Large fluorinated organic cations incorporation is an attractive method for enhancing the intrinsic stability of halide perovskites due to their high dipole moment and moisture-resistant nature. However, a fluorinated cation has a larger ionic size than its non-fluorinated counterpart, falling within the upper boundary of the mixed-cation incorporation. Here, we report on the intrinsic stability of mixed Methylammonium (MA) lead halides at different concentrations of large cation incorporation, namely, ehtylammonium (EA; [CH3CH2NH3]+) and 2-fluoroethylammonium (FEA; [CH2FCH2NH3]+). Density functional theory (DFT) calculations of the enthalpy of the mixing and analysis of the perovskite structural features enable us to narrow down the compositional search domain for EA and FEA cations around concentrations that preserve the perovskite structure while pointing towards the maximal stability. This work paves the way to developing design principles of a large cation mixture guided by data analysis of DFT data. Finally, we present the automated search of the minimum enthalpy of mixing by implementing Bayesian optimization over the compositional search domain. We introduce and validate an automated workflow designed to accelerate the compositional search, enabling researchers to cut down the computational expense and bias to search for optimal compositions.

Effects of catanionic surfactant mixture adsorption on the wettability of PTFE and PMMA

Surfactants can regulate the wettability of a liquid on a solid substrate as they adsorb to solid-liquid and gas-liquid interfaces. In the present work, a catanionic surfactant mixture, sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (C12TAB) mixed at a molar ratio of 2:1, showed outstanding synergistic effect in improving the wettability of low energy substrates (PTFE and PMMA). The adsorption behaviors of the catanionic surfactant mixture on PTFE and PMMA substrates were studied. The surface tensions and contact angles of aqueous solutions of SDS, C12TAB, and their mixture on PTFE and PMMA were measured, and the adhesion tension and adhesion work were calculated. Compared to individual SDS and C12TAB, the SDS-C12TAB mixture formed a compactly arranged layer at the PTFE-aqueous interface, thereby leading to a more significant hydrophilic modification of PTFE. In the PMMA system, the SDS-C12TAB mixture adsorbed to the PMMA-aqueous interface through acid-base interactions between the positively charged surfactant headgroups and the basic groups at PMMA surface and increased the hydrophobicity of the PMMA substrate at low surfactant concentrations. When the surfactant concentration exceeded the critical micelle concentration (CMC), the surfactant started to adsorb to the PMMA-aqueous interface through hydrophobic interactions between the hydrophobic surfactant tails and the nonpolar sites at PMMA surface, which further improved the wettability of PMMA. Overall, the wettability of low energy substrates can be significantly improved under the strong synergistic effect of commercial anionic and cationic surfactants without need of complex synthesis of new amphiphiles. Therefore, the catanionic surfactant mixtures may be a very promising system for regulating wettability.

Terahertz Wave Absorption Property of all Mixed Organic-Inorganic Hybrid Perovskite Thin Film MA(Sn, Pb)(Br, I)3 Fabricated by Sequential Vacuum Evaporation Method.

All mixed hybrid perovskite (MA(Sn, Pb)(Br,I)3) thin film was fabricated by sequential vacuum evaporation method. To optimize the first layer with PbBr2 and SnI2, we performed different annealing treatments. Further, MA(Sn, Pb)(Br, I)3 thin film was synthesized on the optimized first layer by evaporating MAI and post-annealing. The formed hybrid perovskite thin film exhibited absorptions at 1.0 and 1.7 THz with small absorbance (<10%). Moreover, no chemical and structural defect-incorporated absorption was found. In this study, the possibility of changing terahertz absorption frequency through the mixture of metal cations (Sn+ and Pb+) and halogen anions (Br− and I−) was verified.

Investigation of Opto-Electronic Properties and Stability of Mixed-Cation Mixed-Halide Perovskite Materials with Machine-Learning Implementation

The feasibility of mixed-cation mixed-halogen perovskites of formula AxA’1−xPbXyX’zX”3−y−z is analyzed from the perspective of structural stability, opto-electronic properties and possible degradation mechanisms. Using density functional theory (DFT) calculations aided by machine-learning (ML) methods, the structurally stable compositions are further evaluated for the highest absorption and optimal stability. Here, the role of the halogen mixtures is demonstrated in tuning the contrasting trends of optical absorption and stability. Similarly, binary organic cation mixtures are found to significantly influence the degradation, while they have a lesser, but still visible effect on the opto-electronic properties. The combined framework of high-throughput calculations and ML techniques such as the linear regression methods, random forests and artificial neural networks offers the necessary grounds for an efficient exploration of multi-dimensional compositional spaces.

Propagation of CJD Prions in Primary Murine Glia Cells Expressing Human PrPc.

There are various existing cell models for the propagation of animal prions. However, in vitro propagation of human prions has been a long-standing challenge. This study presents the establishment of a long-term primary murine glia culture expressing the human prion protein homozygous for methionine at codon 129, which allows in vitro propagation of Creutzfeldt–Jakob disease (CJD) prions (variant CJD (vCJD) and sporadic CJD (sCJD) type MM2). Prion propagation could be detected by Western blotting of pathological proteinase K-resistant prion protein (PrPSc) from 120 days post exposure. The accumulation of PrPSc could be intensified by adding a cationic lipid mixture to the infectious brain homogenate at the time of infection. Stable propagation of human prions in a long-term murine glia cell culture represents a new tool for future drug development and for mechanistic studies in the field of human prion biology. In addition, our cell model can reduce the need for bioassays with human prions and thereby contributes to further implementation of the 3R principles aiming at replacement, reduction and refinement of animal experiments.

Abstract 2332: Modifying bioavailability of ATP and measuring metabolic response in HeLa cells

Abstract Introduction: Since studies by Otto Warburg demonstrated that cancer cells had markedly reduced oxidative phosphorylation (OXPHOS) under conditions of high oxygen tension (Warburg Effect/aerobic glycolysis), metabolic reprogramming has become a fundamental hallmark of cancer. While numerous discoveries have revealed highly specific metabolic differences between cancer cells, utilization of aerobic glycolysis as the primary means of ATP generation remains one of the most common metabolic alterations observed across a range of cancers. There is growing interest in understanding the multifaceted role ATP plays in cancer development, progression and chemotherapeutic resistance. Using the man-made protein DX, which chelates ATP with high specificity and affinity, we have begun to untangle these roles by significantly reducing cytosolic ATP and investigating cellular response. Hypothesis: Delivery of DX into HeLa cancer cells will reduce intracellular bioavailable ATP and induce an adaptive metabolic response. Methods: A cationic lipid mixture was complexed with active, purified DX protein to generate a DX/lipid complex capable of delivering the protein to the cytoplasm of HeLa cells. To confirm the successful delivery of DX, immunofluorescent microscopy was performed (DYKDDDDK tag monoclonal antibody, Alexa Fluor 647) at various time points following DX transfection. The impact of DX on cell viability was determined using a tetrazolium-based colorimetric cell viability assay and a caspase 3/7 assay. To correlate phenotypic/viability change with DX activity, bioavailable ATP levels were measured at specific time points following DX delivery. Additionally, the relative contribution of glycolysis and OXPHOS to the total ATP production rate was measured using the label-free XF Real Time ATP Rate Assay (XFe96 Seahorse, Agilent Technologies) over time post DX transfection. Results: In a time- and dose- dependent manner, DX negatively impacted cell growth and induced cell death via apoptosis, at a time concomitant with a decrease in bioavailable ATP. In response to DX over time, the total ATP production rates in HeLa cells significantly decreased. Importantly, this reduction in the rate of ATP production was associated with a metabolic program that was primarily glycolytic (70%) with a smaller contribution from OXPHOS (30%) 24 h post DX transfection. Conclusion: Advances in protein engineering have made it possible to create artificial proteins with specific functions. In addition to direct clinical applications, synthetic proteins can be developed into powerful experimental tools to resolve biological enigmas. Direct delivery of DX potentiated energy flux in HeLa cells in an unbiased manner, independent of metabolic pathway interference. This work establishes DX as a useful tool for examination of cancer cell metabolism in response to ATP stress. Citation Format: Taha Muhammad, Ashley Brown, Selina Martinez, John C. Chaput, Jeffrey Norris, Shaleen Korch. Modifying bioavailability of ATP and measuring metabolic response in HeLa cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2332.

Efficient removal of anionic, cationic textile dyes and salt mixture using a novel CS/MIL-100 (Fe) based nanofiltration membrane

The purification of hazardous textile dyeing wastewater has exhibited many challenges because it consists of a complex mixture, including dyestuff, additives, and salts. It is necessary to fabricate membranes with enhanced permeability, fouling resistance, stability, and superior dyes and salts removal from wastewater. Incorporating a highly water stable metal-organic framework (MOFs) into membranes would meet the requirements for the efficient purification of textile wastewater. In this study, nanofiltration (NF) membranes are fabricated by incorporating MIL-100 (Fe) into the chitosan (CS) through film casting technique. The effect of MIL-100 (Fe) loadings on chitosan characterized by FT-IR, XRD, contact angle measurement, FESEM-EDS, XPS, zeta potential, and surface roughness analysis. The membrane characterization confirmed the enhanced surface roughness, pore size, surface charge, and hydrophilicity. The CS/MIL-100 (Fe) membrane exhibited an improved pure water flux from 5 to 52 L/m2h as well as 99% rejection efficiency for cationic methylene blue (MB) and anionic methyl orange (MO). We obtained the rejection efficiency trend for the MB mixed salts in the order of MgSO4 (Mg2+ - 51.6%, SO42− - 52.5%) > Na2SO4 (Na+ - 26.3%, SO42− - 29.3%) > CaCl2 (Ca2+ - 21.4%, Cl− - 23.8%) > NaCl (Na+ - 16.8%, Cl− - 19.2%). In addition, the CS/MIL-100 (Fe) composite membrane showed excellent rejection efficiency and antifouling performances with high recycling stability. These stunning results evidenced that the CS/MIL-100 (Fe) nanofiltration membrane is a promising candidate for removing toxic pollutants in the textile dyeing wastewater.

Anionic and Cationic Surfactant Synergism: Minimizing Precipitation, Microemulsion Formation, and Enhanced Solubilization and Surface Modification

AbstractAnionic–cationic surfactant mixtures are known to exhibit synergistic effects (e.g., low critical micelle concentration, ultralow interfacial tension, middle phase microemulsion formulation, and increased solubilization and adsolubilization). However, the anionic–cationic surfactant mixtures are also prone to form other unique phases such as precipitates, gels, and coacervates in place of middle‐phase microemulsions. Research summarized in this article demonstrates that asymmetric anionic–cationic surfactant mixtures have been shown to promote middle‐phase microemulsions instead of these other phases, albeit with a slight decrease in synergism when using these asymmetric mixtures. The use of anionic–cationic surfactant mixtures also is shown to enhance or decrease surfactant adsorption depending on anionic–cationic surfactant ratios. Middle‐phase microemulsion formation is demonstrated using anionic‐rich or cationic‐rich alcohol‐free microemulsions by anionic–cationic ratio scans while also reducing or eliminating electrolyte requirement. Solubilization and adsolubilization are shown to increase for mixed anionic–cationic surfactant systems, especially for hydrophobic solutes. Thus, by exploiting these synergisms while avoiding phase separation, properly designed anionic–cationic surfactant mixtures can be advantageous for a wide range of applications.

Protamine-Based Strategies for RNA Transfection.

Protamine is a natural cationic peptide mixture mostly known as a drug for the neutralization of heparin and as a compound in formulations of slow-release insulin. Protamine is also used for cellular delivery of nucleic acids due to opposite charge-driven coupling. This year marks 60 years since the first use of Protamine as a transfection enhancement agent. Since then, Protamine has been broadly used as a stabilization agent for RNA delivery. It has also been involved in several compositions for RNA-based vaccinations in clinical development. Protamine stabilization of RNA shows double functionality: it not only protects RNA from degradation within biological systems, but also enhances penetration into cells. A Protamine-based RNA delivery system is a flexible and versatile platform that can be adjusted according to therapeutic goals: fused with targeting antibodies for precise delivery, digested into a cell penetrating peptide for better transfection efficiency or not-covalently mixed with functional polymers. This manuscript gives an overview of the strategies employed in protamine-based RNA delivery, including the optimization of the nucleic acid’s stability and translational efficiency, as well as the regulation of its immunostimulatory properties from early studies to recent developments.

Molecular dynamic (MD) simulation and electrochemical assessments of the Satureja Hortensis extract for the construction of effective zinc-based protective film on carbon steel

In this work, for the first time, the Satureja Hortensis leaves was extracted by ultra-pure water solution and then, the synergistic inhibition effect of various mixtures of Satureja Hortensis extract (SHE) and zinc cations on carbon steel corrosion in 3.5% saline (NaCl) solution was investigated. The proposed compounds' effectiveness in carbon steel corrosion mitigation was surveyed by polarization and EIS tests. The inhibition efficiency of 99.34% was recorded for 700 ppm Zn + 300 ppm SHE. Surface characterizations were conducted employing scanning electron microscope (SEM) equipped with EDX, ultraviolet–visible (UV–Vis) analysis, Fourier transmission infrared (FTIR) spectroscopy, grazing incidence X-ray diffraction (GIXRD), and contact angle (CA) analysis which vividly proved the results of the electrochemical investigation. A mixed protection behavior was observed according to the polarization test results. Molecular dynamics (MD) simulation results complemented the experimental findings in affording insights into the adsorption mechanism at the atomic/molecular scale.

Temperature- and Composition-Induced Multiarchitectural Transitions in the Catanionic System of a Conventional Surfactant and a Surface-Active Ionic Liquid

The mixture of the cationic surfactant, cetyltrimethylammonium bromide (CTAB), and anionic surface-active ionic liquid, 1-butyl-3-methylimidazoliumdodecyl sulfate (bmimDS), has been studied as a function of the mole fraction of CTAB, XCTAB, with the total surfactant concentration fixed at 50 mM using turbidity measurements, rheology, dynamic light scattering, differential scanning calorimetry, small-angle neutron scattering, and small-angle X-ray scattering techniques. The catanionic mixture has been found to exhibit phase transitions from vesicles to micelles as a function of temperature, with some mole fractions of CTAB showing dual transitions. Solutions of XCTAB = 0.2 to 0.5 exhibited a single transition from vesicles to cylindrical micelles at 45 °C. With an increase in the mole fraction of CTAB from 0.55 to 0.65, dual structural transitions at 30 and 45 °C were observed. The microstructural transition at 30 °C is ascribed to the vesicle aggregation process with smaller vesicles fusing into bigger ones, whereas the transition at 45 °C was evaluated to be the vesicle-to-cylindrical micelle transition. However, at higher mole fractions of CTAB, XCTAB from 0.65 to 0.90, a single transition from vesicles to small cylindrical/spherical micelles was observed in the solutions, at a lower temperature of 30 °C. To the best of our knowledge, such a microstructural transitions as a function of temperature in a single mixture of cationic and anionic surfactants without any additive has not been reported so far.

Application of modified green algae Nannochloropsis sp. as adsorbent in the simultaneous adsorption of Methylene Blue and Cu(II) cations in solution

Biomass of algae is a very potent adsorbent for absorbing aqueous waste containing heavy metals and organic dyes. This study purposes to confirm the ability of adsorbents from green algae Nannochloropsis sp. modified with silica (ASN) and followed by coating magnetite particles (ASN-MPs) to absorb simultaneously the mixture of Methylene Blue (ME) and Cu(II) cations in aqueous solution. Simultaneous sorption of ME and Cu(II) cations to ASN and ASN-MPs was carried out by the batch method with the interaction pH condition 7, contact time 90 min, and initial concentrations of ME and Cu(II) cations (0.1–1.0 mM). Based on adsorption data, Cu(II) cations have a greater adsorption rate and capacity (qm) compared to ME at the same contact time and initial concentration. The adsorption capacity (qm) values of the bi-component ME and Cu(II) cation mixture in ASN and ASN-MPs were 1.39 × 10− 1 and 5.32 × 10− 1 mmol g− 1, respectively, with the binary Langmuir adsorption isotherm constant for Cu(II) cations greater than ME. Modified adsorbent from algae Nannochloropsis sp. with silica matrix and magnetite particle coating is an adsorbent that has a high effectiveness in the collective sorption of ME and Cu(II) cations. Therefore, these adsorbents can be used for the adsorption of cation mixtures of heavy metals and organic dyes that are cationic in solution.