Homogeneous Aqueous Solution Research Articles

Soft-hard zwitterionic additives for aqueous halide flow batteries.

Aqueous redox flow batteries with halide-based catholytes (where the halogen atom (X) is Br or I) are promising for sustainable grid energy storage. However, the formation of polyhalides during electrochemical charging and the associated phase separation into X2 limits the operable state of charge (SoC), results in vaporization and self-discharge inefficiencies, and spurs complete device failure1-3. Here we introduce soft-hard zwitterionic trappers (SH-ZITs) as complexing agents composed of a polyhalide-complexing 'soft' cationic motif and a water-soluble 'hard' anionic motif to enable homogeneous halide cycling. More than 300 structures were designed and 13 were characterized, showcasing the ability to complex polyhalides in homogeneous aqueous solution, to deter cation-exchange membrane crossover and to alter the electrochemical electrode mechanism. In flow battery cycling at a standard catholyte SoC of 66.6 per cent (stoichiometrically X3-), an average coulombic efficiency of more than 99.9 per cent at 40 milliamperes per square centimetre with no apparent decay was observed after more than 1,000 cycles over 2 months, with stability at elevated temperatures also demonstrated. Interestingly, SH-ZITs enable homogeneous cycling of the halide catholyte up to 90 per cent SoC at 2 moles per litre (47.7 ampere-hours per litre) for bromide, revealing previously unknown polyhalide regimes to be studied. Ultimately, SH-ZIT enables ultrahigh catholyte capacity utilization up to over 120 ampere-hours per litre at 80 per cent SoC with homogeneous cycling as well as the ability to pair with a zinc anode in a hybrid flow battery.

Azido derivatives of sesquiterpene lactones: Synthesis, anticancer proliferation, and chemistry of nitrogen-centered radicals

Sesquiterpene lactones (SLs) such as parthenolide (PTL) and dehydroleucodine (DhL) selectively kill cancer cells without exerting normal tissue toxicity, potentially due to presence of α-methylene-γ-lactone (αMγL) fragment. We hypothesize that the addition of an azido group to the αMγL fragment of PTL or DhL further augments their anticancer properties as well as radiation sensitivity of cancer cells. Azido-SLs containing the azido group at the C14 methyl position of PTL (i.e., azido-melampomagnolide B, AzMMB) while preserving the mechanistically crucial exomethylene unit of αMγL fragment were also prepared. Sham-irradiated (i.e., unirradiated control) or irradiated human breast cancer cells (MCF7) were treated with different concentrations of azido-PTL (AzPTL) or azido-DhL (AzDhL) along with parental SLs. Proliferation rate of MCF7 cells were measured by MTT-assay, and their colony forming ability was determined by colony formation assay. Both AzPTL and AzDhL significantly suppress proliferation rate and colony forming ability of MCF-7 cells. AzPTL suppressed colony forming ability, not cellular proliferation, following irradiation to a greater extent than PTL at lower concentrations (5 and 10 μM). Electron spin resonance (ESR) studies were performed employing gamma-irradiated homogeneous supercooled aqueous solutions to investigate radical formation through addition of radiation-mediated prehydrated electrons to the azide group of AzPTL and AzDhL and to follow subsequent reactions of these radicals. In AzPTL, formation of a tertiary carbon-centered radical plausibly via a metastable aminyl radical was observed, whereas AzDhL produced both π-aminyl and α-azidoalkyl radicals. These radicals may contribute to the antitumor activities of AzPTL and AzDhL.

Design and simulation of neutron radiography system for an aqueous homogeneous solution reactor

AHR reactors are known for the production of radiopharmaceuticals. The ARGUS reactor is one of the most famous of these reactors, which has been designed originally for radioisotopes production. The ARGUS reactor produces a suitable neutron flux that can be used for other applications such as neutron radiography (NR). Here, a NR system is designed step by step using the Monte Carlo method. The length of the collimator, divergence angle, diameter of the aperture, and thermal column dimension are designed. The designed aperture and thermal column are selected from boron carbide and heavy water, respectively. The depth of the thermal column is changed until the ratio of thermal neutrons to total neutrons (TNC) reached above 90%. The hole inside the thermal column is designed and internal lining is done. The inner lining is made of cadmium and had a thickness of 1 mm, and the space between the inner and outer lining is filled with lead. To reduce the gamma dose to acceptable values, the position of the collimator is changed instead of using a gamma filter. By changing the depth of the hole and creating the convergence angle to the hole, the flux of thermal neutrons will be 1.8E+6 n.cm−2s−1 that satisfy the IAEA suggested values for NR. Then, the uniformity of the radiation field of the neutron flux output from the collimator is obtained. At the end, images of SI and BPI standards are recorded. The good quality and contrast of these images showed the acceptable design of the NR system for the ARGUS reactor.

ALIGNMENT OF FINGERING PATTERN INDUCED BY AN INTERFACIAL NEUTRALIZATION REACTION

In this paper, we numerically study buoyancy-driven chemoconvective instabilities in a vertically oriented Hele-Shaw cell. At the beginning, the cavity is filled with a homogeneous aqueous solution of a strong inorganic alkali, and this system is statically stable. We assume that the upper boundary is free, and a fixed value of the concentration of a strong inorganic acid is set there. After bringing the reactants into contact, density stratification quickly becomes unstable due to a neutralization reaction, resulting in density fingering. The mathematical model includes the effect of producing a new amount of solvent (water). We show that this effect is a reason for the sudden alignment of salt fingers that we previously observed in experiments. In this work, we carry out a formal parametric study of the system with a change in the dimensionless parameter responsible for the intensity of water production. One can interpret this variation as a sequential consideration of substances from the homologous series of alkalis. We show that there exists a critical value of the parameter, crossing which one can observe a spontaneous transition from an irregular fingering pattern to cellular chemoconvection. The latter looks like a system of fingers tightly pressed against each other with tips aligned along a horizontal line. The lower boundary of the vortices uniformly moves down. We found that instead of the usual coarsening of the structure, one observes an increase in the aspect ratio of vortices. We investigate the dynamics of the lower boundary of the fingering pattern and changes in the pattern wavelength. Complex rearrangements of the reaction front, which include the processes of plume creation and coalescence, are illustrated using space-time diagrams.

Decolouration of azo dyes by radicals generated from K2S2O8 automatically in homogeneous aqueous solutions

In this work, at 15 °C and 25 °C, authors study the decolouration reactions (or degradation reactions or oxidation reactions) of 0.10 mM azo dyes (methyl orange and congo red) by (1) K2S2O8 and (2) Co2+/K2S2O8, expounding the roles of K2S2O8 and Co2+: K2S2O8 can oxidize azo dyes automatically in water by radicals; Co2+ has catalysis for oxidation of K2S2O8, whether Co2+ is from CoSO4 or Co(NO3)2, CoCl2, CoAc2. The decolouration degree of azo dyes in all systems quickens with the increase of the initial concentration of K2S2O8 and the reaction temperature. In the presence and absence of Co2+, comparative experiments are done between the oxidation of K2S2O8 and oxone, K2S2O8 shows weaker oxidation than oxone. The decolouration reaction of methyl orange (MO) in the system of (0.10 mM MO + 2.00 mM K2S2O8) accords with the second order reaction, the reaction rate constants are 4.789 M−1 min−1 at 15 °C and 5.894 M−1 min−1 at 25 °C respectively, the activation energy Ea is 14813 J/mol, and Arrhenius equation is k = 2.328 exp[-14813/(RT)].

Effect of inorganic particles on the rheological properties of nano-SiO2 grafted modified polymers

Polymer flooding technology has become the most widely utilized chemical flooding technology in the world. The polymer structure gradually grows from linear to branched and hyperbranched as reservoir variability increases and polymer flooding technology advances. In this study, the nano-SiO2 was first controllably modified, and subsequently, a series of nano-SiO2 grafted modified polymers (MNSP) were synthesized using homogeneous aqueous solution polymerization with modified nano-SiO2 and another functional monomer. The rheological properties of MNSP were analyzed by using the MCR 301 rheometer; then, the mechanism of the influence of the concentration and the modification degree of nano-SiO2 on the rheological properties of MNSP was explored from the microscopic standpoint. The results demonstrate that at a salinity of 3 × 104 mg/L and temperature of 85 °C, the viscosity of the MNSP polymer is superior to that of the standard amphiphilic polymer APC16 whose synthesized monomers do not include nano-SiO2. When the concentration and the modification degree of nano-SiO2 were increased, the solution viscosity first increased and then decreased, and this is mostly due to the addition of inorganic nanoparticles, which stimulates the creation of a three-dimensional network structure and improves the solution characteristics of MNSP. However, too much modified SiO2 addition will interfere with polymerization between various monomers. The modification degree of the nano-SiO2 mostly influences the density of the polymer-formed network structure, the active sites on the modified nano-SiO2 surface rise as the degree of modification increases, as does spatial site resistance, resulting in inferior polymer characteristics. The findings of the experiments reveal fresh ideas for inorganic particles compounding organic polymers and expand the use area of polymers in the oilfield.

Multiple-Stimuli-Responsive Surfactant-Free Microemulsions Based on Hydrophobic Deep Eutectic Solvents.

Hydrophobic deep eutectic solvents (HDESs) have been applied to colloidal systems such as microemulsions, despite the development of stimulus-responsive HDESs still being in a preliminary stage. Here, menthol and indole were hydrogen bonded to form CO2-responsiveness HDES. A surfactant-free microemulsion constituted of HDES (menthol-indole) as the hydrophobic phase, water as the hydrophilic phase, and ethanol as the double solvent was demonstrated to be CO2- and temperature-responsive. Dynamic light scattering (DLS) proved the single-phase region of the phase diagram, while conductivity and polarity probing techniques confirmed the kind of microemulsion. The ternary phase diagram and DLS methods were used to investigate the responsiveness of CO2 and effect temperature on the microemulsion drop size and behavior of the phase of the HDES/water/ethanol microemulsion. The findings revealed that when temperature increased, the homogeneous phase region increased. The droplet size in the homogeneous phase region of the associated microemulsion may be reversibly and accurately adjusted by adjusting the temperature. Surprisingly, a slight temperature change can cause a significant phase inversion. Furthermore, in the system, there was no demulsification in time for the CO2/N2 responsiveness process but rather the production of a homogeneous and pellucid aqueous solution.

Time-Resolved Atomistic Imaging and Statistical Analysis of Daptomycin Oligomers with and without Calcium Ions.

Daptomycin (DP) is effective against multiple drug-resistant Gram-positive pathogens because of its distinct mechanism of action. An accepted mechanism includes Ca2+-triggered aggregation of the DP molecule to form oligomers. DP and its oligomers have so far defied structural analysis at a molecular level. We studied the ability of DP molecule to aggregate by itself in water, the effects of Ca2+ ions to promote the aggregation, and the connectivity of the DP molecules in the oligomers by the combined use of dynamic light scattering in water and atomic-resolution cinematographic imaging of DP molecules captured on a carbon nanotube on which the DP molecule is installed as a fishhook. We found that the DP molecule aggregates weakly into dimers, trimers, and tetramers in water, and strongly in the presence of calcium ions, and that the tetramer is the largest oligomer in homogeneous aqueous solution. The dimer remains as the major species, and we propose a face-to-face stacked structure based on dynamic imaging using millisecond and angstrom resolution transmission electron microscopy. The tetramer in its cyclic form is the largest oligomer observed, while the trimer forms in its linear form. The study has shown that the DP molecule has an intrinsic property of forming tetramers in water, which is enhanced by the presence of calcium ions. Such experimental structural information will serve as a platform for future drug design. The data also illustrate the utility of cinematographic recording for the study of self-organization processes.

Stereoselectivity of Interaction of Nonsteroidal Anti-Inflammatory Drug S-Ketoprofen with L/D-Tryptophan in Phospholipid Membranes.

The mechanisms of stereoselectivity of the interaction of chiral drugs with active sites of enzymes and cell receptors attract significant attention. The first reason is the difference in therapeutic activity of the enantiomers of the common drugs. Another reason is the interest in the role of chiral inversion of amino acids involved in various peptides in the development of many diseases including Alzheimer’s, Parkinson’s, type II diabetes, and a number of other pathological conditions. In our study we use elementary chemical process—electron transfer (ET) to simulate individual stages of ligand–receptor and enzyme–substrate interactions. In particular, previous studies of photoinduced ET in chiral donor-acceptor dyads consisting of the nonsteroidal anti-inflammatory drug (R/S)-ketoprofen and (L)-tryptophan show the stereo and spin selectivity of ET in diastereomers. The present study is devoted to the interaction of (S)-ketoprofen with L- and D-enantiomers of tryptophan in homogeneous aqueous solution and in phospholipid membranes. The study was done using the NMR technique and molecular modeling. These approaches confirm efficient penetration of ketoprofen into the lipid bilayer and binding with tryptophan molecule. The short-lived paramagnetic intermediates formed during the photoinduced ET from electron donor tryptophan to ketoprofen have been detected using the chemically induced dynamic nuclear polarization (CIDNP) technique. It was found that S-ketoprofen interacts stereoselectively with tryptophan enantiomers in the lipid membrane. The formation of the ketyl radical of ketoprofen under irradiation leads to the oxidation of membrane lipids and may be the cause of ketoprofen phototoxicity. However, in contrast to a homogeneous solution in phosphate buffer saline, where the amino acid tryptophan accelerates the photodecomposition of KP due to intramolecular hydrogen transfer, tryptophan in a lipid membrane significantly reduces the rate of photodegradation due to a reversible electron (or hydrogen) transfer reaction. The stereoselectivity in the rate of KP and lipids decomposition under UV irradiation of S-ketoprofen in the presence of tryptophan enantiomers in lipid bilayer has been detected.

The effect of concentration-dependent diffusion on double-diffusive instability

The article studies the stability of a two-layer miscible system to the double-diffusive instability. The system is placed in a vertical Hele–Shaw cell and is composed of two homogeneous aqueous solutions initially separated by a narrow transient zone. We have restricted our consideration to the initially stable density stratification that precludes the Rayleigh–Taylor instability. The main objective of the study is to elucidate the effect of a concentration-dependent diffusion coefficient, which has been commonly ignored by researchers. Assuming linear dependence of the diffusion coefficient of each solute and using Picard's iteration scheme, we have derived a closed-form analytical expression for the time-dependent density profile. This permits the stability boundary to be established for a two-layer system with respect to the double-diffusive instability by taking into account the effect of a concentration-dependent diffusion coefficient. The obtained analytical result has been substantiated by the results of direct numerical simulation. The experiments have shown that a successive increase in the concentrations of both solutes, with their ratio remaining unchanged, can lead to opposite results. In the case of a NaNO3-H2SO4 pair, the two-layer system, being stable at low concentrations, becomes unstable as the concentrations proportionally increase, giving rise to convective motion in the form of salt fingers. On the contrary, a two-layer system consisting of LiCl and NaNO3 solutions is stabilized with increasing concentrations of dissolved substances. A further increase in the concentrations of these substances causes mechanical equilibrium breaking and subsequent formation of the so-called diffusive-layer convection. The experimental results are in good agreement with the theoretical predictions.

The impacts of elevated temperature and mNaCl for in situ Raman quantitative calibration of dissolved gas species

In the past ten years, Raman spectroscopy analysis has been widely applied to the quantification of the components of hydrothermal fluids and fluid inclusions. However, the accuracy of the quantitative results of Raman spectroscopy is highly dependent on the quantitative calibration model. How temperature and salinity affect quantitative calibration models remains an unsolved question, which severely hinders the accurate geochemical characterization of hydrothermal fluids and fluid inclusions. In this study, the Raman spectra of the symmetric stretching mode of methane (~ 2917 cm−1) in homogeneous CH4-containing aqueous solutions were obtained at temperatures from 25 to 300 °C, pressures from 0.1 to 40 MPa, and mNaCl from 0 to 5.0 mol/kg to research the effects of elevated temperature and salinity on the Raman spectroscopy quantitative measurement of gas species, and two Raman calibration models of CH4 that reference OH bending and stretching bands were established. Both models show high dependence on salinity. Large measurement errors, causing underestimation of methane concentrations by up to 57.5%, occur if the salinity of the fluids is not taken into account during the calibration. The contributions of the Raman scattering cross section (RSCS) and molar density to the change of quantification factors (QFs) were quantified, and the results showed that the variation of the RSCS is the main factor determining QF values. The significant discrepancy between the measured and predicted QFs demonstrates that changes in the peak areas of both H2O and CH4 contribute to the dependence of quantitative calibration models on temperature and salinity.

Ligand Controls the Activity of Light-Driven Water Oxidation Catalyzed by Nickel(II) Porphyrin Complexes in Neutral Homogeneous Aqueous Solutions.

Finding photostable, first‐row transition metal‐based molecular systems for photocatalytic water oxidation is a step towards sustainable solar fuel production. Herein, we discovered that nickel(II) hydrophilic porphyrins are molecular catalysts for photocatalytic water oxidation in neutral to acidic aqueous solutions using [Ru(bpy)3]2+ as photosensitizer and [S2O8]2− as sacrificial electron acceptor. Electron‐poorer Ni‐porphyrins bearing 8 fluorine or 4 methylpyridinium substituents as electron‐poorer porphyrins afforded 6‐fold higher turnover frequencies (TOFs; ca. 0.65 min−1) than electron‐richer analogues. However, the electron‐poorest Ni‐porphyrin bearing 16 fluorine substituents was photocatalytically inactive under such conditions, because the potential at which catalytic O2 evolution starts was too high (+1.23 V vs. NHE) to be driven by the photochemically generated [Ru(bpy)3]3+. Critically, these Ni‐porphyrin catalysts showed excellent stability in photocatalytic conditions, as a second photocatalytic run replenished with a new dose of photosensitizer, afforded only 1–3 % less O2 than during the first photocatalytic run.

Ligand Controls the Activity of Light‐Driven Water Oxidation Catalyzed by Nickel(II) Porphyrin Complexes in Neutral Homogeneous Aqueous Solutions

AbstractFinding photostable, first‐row transition metal‐based molecular systems for photocatalytic water oxidation is a step towards sustainable solar fuel production. Herein, we discovered that nickel(II) hydrophilic porphyrins are molecular catalysts for photocatalytic water oxidation in neutral to acidic aqueous solutions using [Ru(bpy)3]2+ as photosensitizer and [S2O8]2− as sacrificial electron acceptor. Electron‐poorer Ni‐porphyrins bearing 8 fluorine or 4 methylpyridinium substituents as electron‐poorer porphyrins afforded 6‐fold higher turnover frequencies (TOFs; ca. 0.65 min−1) than electron‐richer analogues. However, the electron‐poorest Ni‐porphyrin bearing 16 fluorine substituents was photocatalytically inactive under such conditions, because the potential at which catalytic O2 evolution starts was too high (+1.23 V vs. NHE) to be driven by the photochemically generated [Ru(bpy)3]3+. Critically, these Ni‐porphyrin catalysts showed excellent stability in photocatalytic conditions, as a second photocatalytic run replenished with a new dose of photosensitizer, afforded only 1–3 % less O2 than during the first photocatalytic run.

Synthesis of an Eco-friendly Bamboo Cellulose-grafted-ployacrylamide Flocculant and Its Flocculation Performance on Papermaking Wastewater

Flocculation is the first and important step to remove suspended and slightly soluble pollutants in industrial wastewater treatment. Flocculant is just the key element for flocculation process. Polyacrylamide (PAM) is the most widely used flocculant. But it still holds some potential flaws which are ignored by people. An eco-friendly bamboo cellulose-grafted-ployacrylamide flocculant (BC-g-PAM) was then synthesized by free-radical graft copolymerization in homogeneous aqueous solution. The optimal synthesis conditions of the BC-g-PAM was investigated. FTIR, TG, XRD and FESEM were employed to characterize and define its molecular structure and physical characteristics. The BC-g-PAM was also adopted to treat an actual papermaking wastewater. The positive results showed that the BC-g-PAM exhibited an excellent flocculation performance on the papermaking wastewater. The average turbidity removal rate reached 99.7 % and related suspended solids exhibited the corresponding decline. This flocculation also caused a positive effect on the reduction of CODCr and BOD5 of the wastewater. Meanwhile, the BC-g-PAM exhibited an excellent biodegradability. Its degradation rate reached 63.4 % at 90 d in soil extracting solution.

Adaptive Chirality of an Achiral Cage: Chirality Transfer, Induction, and Circularly Polarized Luminescence through Aqueous Host–Guest Complexation

Chirality transfer, induction, and circularly polarized luminescence (CPL) using supramolecular hosts, such as macrocycles and cages, have been explored for wide-ranging applications in chiral reco...

Preparation and applications of wettability-controlled fluoroalkyl end-capped oligomer/cellulose nanofiber composites

Sol-gel reaction of two fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2CHSi(OMe)3)n-RF; RF = CF(CF3)OC3F7; n = 2, 3: RF-(VM)n-RF] in the presence of cellulose nanofiber (CNF) under non-catalytic conditions was found to provide the corresponding fluorinated oligomeric silica/CNF composites [RF-(VM-SiO3/2)n-RF/CNF]. The obtained composites were applied to the surface modification of glass to give a good oleophobic/superhydrophobic characteristic on the composite surface due to the fabrication of the roughness architecture. The RF-(VM-SiO3/2)n-RF/CNF composites were also applied to the surface modification of poly(ethylene terephthalate) [PET] fabric swatch, affording a superoleophilic/superhydrophobic characteristic on the modified fabric surface. Modified PET fabric swatch thus obtained was applicable to not only the separation membrane to separate the mixture of oil/water but also the perfect adsorption of oil droplets spread on water interface. In addition, we have prepared the RF-(VM-SiO3/2)n-RF/CNF composites films by casting homogeneous aqueous methanol solutions containing the corresponding composites. Pristine CNF film afforded the superoleophilic property on the surface; however, it was demonstrated that the obtained transparent colorless CNF composite films can supply highly oleophobic characteristic on the surface.

Fabrication and properties of carboxymethyl chitosan/polyethylene oxide composite nonwoven mats by centrifugal spinning

Carboxymethyl chitosan/polyethylene oxide (CMCS/PEO) mixed composition nonwoven mats with the average mat basis weight of 34.53–49.63 g/m2 were prepared by centrifugal spinning from homogeneous aqueous solution for potential use as wound dressings. The weight fraction composition of CMCS/PEO investigated was 40/60 to 60/40. The CMCS/PEO fibers were found to have normally distributed, monomodal, average diameters ranging from 1.91 μm (55 % CMCS) to 3.22 μm (50 % CMCS). Addition of CMCS to PEO (40 % CMCS) resulted in appearance of a wide angle x-ray diffraction (WXRD) peak at 18.9°. The CMCS and PEO fibers were demonstrated by differential scanning calorimetry and WXRD to be mixtures of the two paracrystalline polymers. The composite nonwoven mats with 60 % weight of CMCS demonstrated Log2 reduction at 24 h against Staphylococcus aureus inoculation (104 cfg/mL).

Preparation of Polymer Composite Membrane Reinforced by Natural Fibers (Fiber and Stem of Date Palm) for Treatment of Industrial Waste Water Residue

The developed industries are utilized natural waste fibers as a clean criteria device. This work utilized natural composite membranes in the treatment of wastewater to remove different pollutants such as heavy metals (Cd, Cr, Cu), chemical groups as (phenolic compound, acid and basic surfactants) in addition to modify pH values. This membrane was manufactured by solution polymerization between polyvinyl alcohol aqueous solution (1/3 PVOH/H2O) and date palm wastes (leaf and stems) at different mixing ratios 30/70, 50/50, and 70/30 wt % from PVOH and different date palm wastes (leaf and stem). These reactants are introduced at 80°C in a batch reactor for one hour with continuous mixing until reach homogenous aqueous solutions. Then left it for half an hour to give stable form then put it in a suitable moulds coated by paraffin film, dried under insulated oven for 3 h. Afterward different utilization conditions were studied such as type of natural waste (leaf and stem), particle size of these wastes 150 and 250 µm, and additive ratios of them 30/70, 50/50, and 70/30, respectively. All prepared composite membrane give good removal for different pollutants as heavy metals and chemical groups with preferences for samples used stem natural wastes and small particle size 250 micron rather than leaf type with 100% removal efficiency for industrial waste water from petroleum refinery . Optimum conditions that give high efficiency for removal are 250 micron particle size, stem type, and 70/30 mixing ratio from this waste, respectively. XRD, SEM, and EDS analysis proved the same above results of excellent selective adsorptive separation of both heavy metals and chemical pollutants groups (phenol and surfactant) for optimum samples nos. 4 and 8.

Selective Gold Recovery from Homogenous Aqueous Solutions Containing Gold and Platinum Ions by Aromatic Amino Acid-Containing Peptides.

There is increasing interest in the development of noble metal separation/recovery processes, especially for applications to “urban mining”. Common separation/recovery processes for noble metals use a solvent (liquid-liquid) extraction technique in hydrometallurgy. However, these processes are time-consuming and not environmentally friendly, because they use organic solvents for sequential metal ion extractions. Electrowinning is an alternative approach for selective metal precipitation that involves controlling the redox potentials of electrodes but requires specialized equipment and generates hydrogen as a byproduct at the cathode surface under dilute conditions. In the present study, we investigated selective gold recovery from a homogenous aqueous solution containing a mixture of dilute HAuCl4 and H2PtCl6 (5.0 × 10−5 M each) and aromatic amino acid-containing peptides (2.0 × 10−4 M each). Gold selectivity was determined by analyzing the compositions of the solids and supernatants obtained from the reaction mixtures. A much higher gold selectivity (gold/platinum (Au/Pt) atomic ratio = 7.5) was obtained using an anthracene-containing peptide compared to peptides containing one or two naphthalene ring(s). Our proposed approach is applicable to the sequential separation of several noble metal ions, such as Au, palladium (Pd), Pt, iridium (Ir) and rhodium (Rh), and simply requires developing aromatics suitable for each noble metal of interest.

Recent Advances in Complex Coacervation Design from Macromolecular Assemblies and Emerging Applications.

Coacervation is a process during which a homogeneous aqueous solution undergoes liquid-liquid phase separation, giving rise to two immiscible liquid phases composed of a colloid-rich coacervate phase in equilibrium with a colloid-poor phase simultaneously. Recent attempts to develop complex coacervation from macromolecular self-assemblies have diversified a large group of novel coacervate-related materials with sophisticated properties and emerging applications. In this review, the most recent progress in the design strategies of macromolecular complex coacervation is discussed with respect to different key parameters, including macromolecular structure, mixing ratio, ionic strength, pH, and temperature, etc. Furthermore, the applications of these multiple-functional coacervate materials, oriented toward advanced encapsulation, are further summarized into several active domains in wastewater treatment, protein purification, food formulation, underwater adhesives, drug delivery, and cellular mimics. Finally, perspectives and future challenges related to the further advancement of macromolecular complex coacervates are proposed.