Background Electrolyte Concentration Research Articles

Comparison of the impacts of the experimental parameters and soil properties on the prediction of the soil sorption of Cd and Pb

The sorption and desorption of heavy metals in soil are important processes influencing their transport through soil and their ultimate fates. Many attempts have been made to predict the solid–liquid portioning coefficients, often required for modeling the transport and fates of heavy metals in a soil system. In the conventional approach, several soil properties, including pH and cation exchange capacity, are used as predictors to estimate sorption constants. While there is empirical evidence that the environmental and solution parameters, often varying with the experimental conditions of the sorption test, influence the measured soil sorption, previous studies have not considered the effects of these experimental parameters on the reported results thoroughly. Disregarding the experimental conditions may result in biased predictions of the sorption constants, resulting in inaccurate risk assessments. Herein, multiple linear regression models are developed to predict the Freundlich equation coefficients of Cd and Pb based on both the soil properties and experimental conditions as explanatory variables. Results show that the proposed model provided better performance than the conventional techniques that only consider the soil properties. It is demonstrated that the impacts of certain experimental parameters, such as liquid–solid ratio and background electrolyte concentration in solution, on the sorption constants were comparable in magnitude to the effects of the soil properties. These findings indicate that different experimental conditions should be accounted for when comparing sorption constants determined in different studies. The proposed approach could be applicable to the estimation of soil sorption constants with range of environmental and solution parameters.

Electrochemical recovery of low concentrated platinum (Pt) on nickel hexacyanoferrate nanoparticles film

The nickel hexacyanoferrate (NiHCF) nanoparticles film coated electrode was firstly used to recover low concentrated Pt(II) (∼ppm) from the dilute solution electrochemically. The film showed compact nanoparticles structure, high redox-active sites (4.6 mmol/g), characterised by Cyclic Voltammetry (CV), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM). There was a prominent recovery effect of Pt(II) on NiHCF film in a well-stirred solution. The recovery of Pt(II) was improved with the potential decreasing but decreased with the background electrolyte concentration rising. And its recovery capacity was up to 498.62 mg/g at -0.6 V (vs. SCE), about occupying 56% of redox-active sites, which was significantly higher than the conventional adsorption process. The presence of Co2+ greatly enhanced the Pt(II) recovery from the dilute solution, since Co2+ inserted into availble Ni-NC-Fe-CN- sites, resulting in a drecrese of static electrostatic field and an increase of boundary laryer effect. Conversely, Ni2+ had an insignificant effect on Pt(II) recovery in agreement with the results of energy dispersive X-ray (EDX). The kinetic considerations indicated that the adsorption process was controlled by a multistep mechanism, and the whole process possibly involved the chemisorption of Pt(II) on NiHCF film firstly and then Pt(II) was reduced into Pt(0).

THERMOCHEMICAL STUDY OF ACID-BASE REACTIONS IN AQUEOUS SOLUTION OF PYRIDOXINE

Vitamin B6 is one of the most important vitamins necessary for the life of living organisms. Vitamin B6, which in the body is represented by coenzyme forms - pyridoxal phosphate and pyridoxamine phosphate, is a part of more than 100 enzymes. As the object of study, we chose pyridoxine. The thermal effects of interaction of the solution of pyridoxine with solutions of nitric acid and potassium hydroxide at 298.15K and ionic strength values of 0.25; 0.5 and 0.75 against the background of electrolyte-supporting potassium nitrate were measured with direct calorimetric method. The measurements were carried out in a calorimeter with an isothermal shell equipped with a 60 cm3 reaction vessel and electric calibration at T = 298.15 ± 0.01 К and P = 100.5 ± 0.7 kPa and automatic recording of the temperature-time curve. Relative measurement error for heats of dissolution of a standard substance was -0.1-0.3%. Calculation of the equilibrium composition of the system taking into account processes a step dissociation and water dissociation was carried out according to the KEV program. The thermal effects of dissociation of pyridoxine in a standard solution were found by extrapolating the heats of stepwise dissociation at fixed values of ionic strength to zero ionic strength. Since the thermal effects of dilution were measured in three concentration ranges of KNO3, the number of experiments in each series was at least three. To calculate the confidence interval of the average value of DН the Student's criterion was taken at a confidence interval of 0.95. Standard thermodynamic characteristics (DrH°, DrG°, DrS°) of reactions of acid-base interaction in aqueous solutions of pyridoxine were calculated. With an increase in the background electrolyte concentration, the endothermicity of stepwise pyridoxine ionization processes increases.

Adsorption of Pb(II) by tourmaline-montmorillonite composite in aqueous phase

In this study, a tourmaline-montmorillonite composite (TMMs) was synthesized by vacuum sintering to adsorb Pb(II) from aqueous phase. Different sintering temperature and proportion of tourmaline (TM) were first investigated by evaluating the adsorption capacity for Pb(II). The results indicated that the proper sintering temperature of the synthesis process and proportion of TM were 800 °C and 30.7% respectively. Batch experiments indicated Pseudo-second-order kinetic model and Freundlich adsorption isotherms fitted well with the adsorption characteristics of Pb(II) on TMMs, indicating that the adsorption progress of Pb(II) on TMMs related to chemical absorption and the maximum adsorption capacity was 303.21 mg/g. The background electrolyte concentration and solution pH have little effect on the adsorption behavior of TMMs. Adsorption mechanism of Pb(II) on TMMs might attribute to the electrostatic and complexation processes such as dissociation of metal ion bonds on the surface, hydroxylation on the surface of minerals, and self-polarization. The structure of TMMs was tested by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). This work provided a good reference for the application of tourmaline on treatment of heavy metals pollution in water.

Self-Propulsion of Active Colloids via Ion Release: Theory and Experiments.

We study the self-propulsion of a charged colloidal particle that releases ionic species using theory and experiments. We relax the assumptions of thin Debye length and weak nonequilibrium effects assumed in classical phoretic models. This leads to a number of unexpected features that cannot be rationalized considering the classic phoretic framework: an active particle can reverse the direction of motion by increasing the rate of ion release and can propel even with zero surface charge. Our theory predicts that there are optimal conditions for self-propulsion and a novel regime in which the velocity is insensitive to the background electrolyte concentration. The theoretical results quantitatively capture the salt-dependent velocity measured in our experiments using active colloids that propel by decomposing urea via a surface enzymatic reaction.

Palladium release from catalytic converter materials induced by road de-icer components chloride and ferrocyanide.

Environmental levels of platinum group elements (PGEs) are rising due to emissions of vehicle catalytic converter (VCC) materials containing palladium, platinum and rhodium. When these PGE-containing VCC materials are exposed to soil and water, coordination complex formation with ligands present in the environment may mobilize PGEs into solution, particularly Pd. Road de-icing salt contains two ligands with high affinities for Pd2+: chloride (Cl-) from NaCl and cyanide (CN-) from ferrocyanide (Fe(CN)64-) anti-caking agents. Batch leaching studies of VCC materials were conducted with solutions representative of de-icer-contaminated road runoff at pH 8 and room temperature for 48h. Ferrocyanide (FC) concentrations of 0μM, 1μM, 2μM and 10μM were tested with background electrolyte concentrations of 0.028M NaCl (1000mg/L Cl-) or 0.028M NaClO4. Palladium release increased with FC concentration, ranging from 0.014±0.002μMPd without FC to 5.013±0.002μMPd at 10μM FC. At 0μM, 1μM and 2μM FC, chloride induced further Pd release, but had no effect at 10μM FC. PHREEQC modeling predicted that the predominant species present in equilibrium with Pd(OH)2(s) were Pd(OH)20 and Pd(CN)42-, and that PdClx2-x complexes had only a minor effect on the total concentration of dissolved palladium. The effect of FC on Pd release was predicted but not the effect of Cl-, indicating possible kinetic control. Platinum was measured above limits of detection (LODs) only at 10μM FC, and rhodium levels were below LODs, consistent with their slower complexation kinetics.

Rapid and efficient removal of acetochlor from environmental water using Cr-MIL-101 sorbent modified with 3, 5-Bis(trifluoromethyl)phenyl isocyanate

The excessive use of acetochlor (ACT), a commonly used herbicide with latent endocrine disrupting functions, causes surface water pollution. The efficient removal of ACT from contaminated water supplies is of paramount importance. In the current work, 3,5-Bis(trifluoromethyl)phenyl isocyanate (BTP) was successfully anchored onto Cr-MIL-101 walls via covalent incorporation to afford Cr-MIL-101-BTP as a novel adsorbent for the high-efficiency removal of ACT in aqueous solutions. The kinetic adsorption process, adsorption isotherms, adsorbent regeneration, and key parameters, such as adsorbent dosage, pH value, and ionic strength, for the adsorption of ACT were studied. Results showed that a pseudo-second-order rate equation effectively describes the adsorption kinetics. The Langmuir model exhibited a better fit to adsorption isotherm than the Freundlich model. Given the π-π stacking and hydrogen bond interaction, the adsorption capacity in Cr-MIL-101-BTP approached a maximum of 312.5 mg/g for ACT, which was considerably higher than the adsorption capacities of many other reported adsorbents. The excellent adsorption characteristics of Cr-MIL-101-BTP toward ACT were preserved in a wide pH range and high concentration of background electrolytes. In addition, the result showed that partition coefficient (PC) of Cr-MIL-101-BTP was 356.14 mg/g/μM at 5 mg/L of ACT concentration, which was found as the outperformer in all tested subjects. The ACT adsorption capacity of Cr-MIL-101-BTP at the breakthrough point was greatly influenced by initial concentration, and could be described by the Thomas model. Regeneration experiments indicated that the Cr-MIL-101-BTP was recycled at least six times without significant loss of adsorption capacity. Moreover, Cr-MIL-101-BTP did not show cytotoxic activity against the tested HepG2 cell lines and did not pose serious risks to Daphnia carinata survival (48 h LC50 = 446.6 μg/mL). These results prefigured the promising potential of Cr-MIL-101-BTP as a novel adsorbent for the efficient removal of ACT from aqueous solutions.

A self-gating proton-coupled electron transfer reduction of hexavalent chromium by core-shell SBA-Dithiocarbamate chitosan composite

We have proposed a novel strategy for the reduction plus adsorption process for hexavalent chromium elimination by thiol functional hybrid materials through a self-gating process. Namely, we exploit that coating dithiocarbamate chitosan at the surface of SBA-15 affords a core-shell composite that undergoes reversible shape transformations while thiol functional groups acted as proton-coupled electron donor for [Cr2O7]2−. The reduction of [Cr2O7]2− to Cr3+ was highly efficient and exceptionally rapid, occurred within 5 min with the reduction amount of 899.66 mg of [Cr2O7]2− / 1 g of nanocomposite as a record high value. During the reduction of [Cr2O7]2−, thiol functional groups (-SH) were oxidized into disulfide linkages (SS), and simultaneously chitosan matrix turned into shrunken structure because of the consuming of protons, preventing any release of Cr3+. Disulfides can also be reversely reduced to thiols by thiosulphates (S2O32−), which was attractive for regeneration and recyclability of the nanocomposite. Moreover, the [Cr2O7]2− elimination through self-gating process was highly selective against a huge concentration of background electrolytes. This alternative strategy ensures the outstanding and stable performance in applied fields, and could be conducted in various pollution control techniques like permeable reactive barriers.

Enthalpies of acid dissociation of l-carnosine in aqueous solution

The enthalpies of l-carnosine interaction with solutions of hydrochloric acid have been measured by calorimetric method in the presence of NaCl at 298.15 K and ionic strength as high as 0.25, 0.50 and 0.75 mol dm−3. The enthalpies of acid dissociation have been determined from the obtained data. The effect of a background electrolyte concentration on the dissociation enthalpy of peptide has been considered. Standard thermodynamic quantities (ΔdisH°, ΔdisG°, ΔdisS°) of the acid dissociation of the dipeptide in aqueous solutions have been determined on the basis of the obtained thermochemical results and available data on the acid dissociation constants corrected for the zero-order ionic strength. Ability to acid dissociation of amino acids in a free state is compared with those for amino acid residues involved in the dipeptide linkage. The alteration of acidity has been connected with variation in hydration of reactivity centers.

Enhanced removal of phenol by novel magnetic bentonite composites modified with amphoteric-cationic surfactants

Magnetic bentonite (MBent) was modified by both amphoteric surfactant (BS) and cationic surfactant (CT). The structural characteristics of BS-CT-MBent were explored along with the factors primarily influencing their effectiveness in phenol sorption. The results indicated that BS-CT-MBent showed high separation potential and good stability. The carbon contents of BS-CT-MBent increased while specific surface areas decreased with increasing the BS and CT loading level. The sorption capacities of BS-CT-MBent for phenol (198.74–205.81 mmol kg−1) were improved compared to MBent (16.34 mmol kg−1). The phenol sorption capacities on BS-CT-MBent increased with an increase of BS or CT loading level, while the phenol sorption efficiency decreased at high BS and CT loading level. The phenol sorption capacities decreased with an increase of pH, temperature and with a decrease of background electrolyte concentration. Hydrophobic phases formed by surfactants were the main phenol sorption domains and the hydrophobic partition was the key mechanism.

Determination of oxaliplatin enantiomers at attomolar levels by capillary electrophoresis connected with inductively coupled plasma mass spectrometry

The aim of this study was to develop a method for the separation of oxaliplatin enantiomers at attomolar concentration levels. A combination of capillary electrophoresis and inductively coupled plasma mass spectrometry was chosen due to their unique characteristics, including fast and easy modification of separation selectivity, and significant limits of detection and linearity. In the first step, we optimized conditions for the separation of oxaliplatin enantiomers including background electrolyte composition and concentration, pH, and type and concentration of the chiral selector. Under optimal conditions, sodium borate buffer pH 9.5, ionic strength 40 mmol L−1, with 60 mg mL−1 sulfated β-cyclodextrin, separation was obtained with a resolution of 2.0. This electrolyte system was then used in the ‘in-house’ connection of capillary electrophoresis with inductively coupled plasma mass spectrometer. In this instance, separation lasted for 9.5 min. Calibrations were linear in the range of 0.1–500 μg mL−1 with R2 of 0.9999. LOD and LOQ values were of 64 ng mL−1 and 116 ng mL−1 of oxaliplatin, respectively. This represents detection of 49 fg or 125 attomol of oxaliplatin enantiomers in the capillary electrophoresis injected sample zone. Finally, the method was successfully applied for detection of oxaliplatin enantiomers in spiked urine samples.

Understanding effect of solution chemistry on heteroaggregation of zinc oxide and copper oxide nanoparticles

The reported presence of mixture of nanoparticles in environmental water warrants developing understanding on their aggregation and fate. This study tried to address this question and focused on understanding effects of pH (3,7 and 10), background electrolyte concentration (1 mM and 10 mM as NaCl) and nanoparticle (NP) concentration (1 and 10 mg/L) on stability of suspension containing mixture of two commonly-found metal oxide-based NP (i.e., ZnO and CuO NPs) in a 6-h study (output variables: aggregation rate constant, settling rate constant, difference in zeta potential, change of metal content in suspension and on aggregates). Two iso-electric point values were obtained: pH 3.08 and 8.33 for mixture suspension in DI (De-ionized) water and pH 5.69 and 8.65 for mixture suspension with 10 mM electrolyte concentration. Settling rate constant and aggregation rate constant values of suspension containing mixture of NPs varied between 0.02 and 0.23 NTU/(NTU-hour) and 0.0002 and 0.03 nm/s, respectively. At natural pH condition, settling rate constant and aggregation rate constant values were obtained to be 0.05 NTU/(NTU- hour) and 0.012 nm/s. The Derjaguin–Landau–Verway–Overbeek (DLVO) analyses indicated that aggregation of mixture of NPs might be happening due to combined effects of ionic layer compression, charge neutralization and van der Waals attraction. Dissolution of nanoparticles was found to be significantly affected by change in pH of suspension. Stability of mixture of nanoparticles was observed to decrease with increasing pH, ionic strength and nanoparticle concentration values. For ZnO and CuO nanoparticles, model equations were developed for predicting their (i) aggregation rate constant, (ii) settling rate constant, (iii) difference in zeta potential, (iv) percentage change of metal in suspension and (v) solid Zn fractions of mixture of nanoparticles as a function of pH, ionic strength and NP concentration. These information are useful in understanding fate of mixture of NPs in suspension as well as in settled solids in natural water bodies and in water treatment systems.

Control of the colloidal depletion force in nonionic polymer solutions by complexation with anionic surfactants

HypothesisCharge, size and concentration of depletants control the magnitude and range of depletion and structural forces. Noncovalent association of nonionic polymers with ionic surfactants may therefore synergistically enhance these forces to an extent that depends on the structure and composition of the resulting complexes. ExperimentsForces were measured between a silica sphere and a silica plate in solutions of Pluronic F108 nonionic poly(ethylene oxide – block – propylene oxide – block – ethylene oxide) triblock copolymers and anionic sodium dodecylsulfate (SDS) surfactants using colloidal probe atomic force microscopy as a function of polymer, surfactant and NaCl background electrolyte concentrations. Trends in the magnitudes of the depletion attraction minimum and the first repulsive maximum in the oscillatory structural force were interpreted with the aid of pyrene solubilization assays, sodium ion-selective electrode analysis, and dynamic light scattering measurements that characterized the formation, charge, and hydrodynamic radius of F108/SDS complexes respectively. FindingsSynergistic enhancement of the depletion force and first repulsive maximum occurred within a finite range of SDS concentrations, to an extent that depended on F108 and NaCl concentrations. This was due mainly to charging of F108/SDS complexes. Size effects were important at low NaCl concentration. Forces measured above the synergistic SDS concentration range were indistinguishable from those in polymer-free SDS solutions due to the appearance of excess unbound SDS micelles.

Compositional and Temperature Effects on the Rheological Properties of Polyelectrolyte-Surfactant Hydrogels.

The rheological properties of hydrogels prepared by physical interactions between oppositely charged polyelectrolyte and surfactant in micellar form were studied. Specifically, hyaluronan was employed as a negatively charged polyelectrolyte and Septonex (carbethopendecinium bromide) as a cationic surfactant. Amino-modified dextran was used as a positively charged polyelectrolyte interacting with sodium dodecylsulphate as an anionic surfactant. The effects of the preparation method, surfactant concentration, ionic strength (the concentration of NaCl background electrolyte), pH (buffers), multivalent cations, and elevated temperature on the properties were investigated. The formation of gels required an optimum ionic strength (set by the NaCl solution), ranging from 0.15–0.3 M regardless of the type of hydrogel system and surfactant concentration. The other compositional effects and the effect of temperature were dependent on the polyelectrolyte type or its molecular weight. General differences between the behaviour of hyaluronan-based and cationized dextran-based materials were attributed to differences in the chain conformations of the two biopolymers and in the accessibility of their charged groups.

Simultaneous determination of metal ions by capillary electrophoresis with contactless conductivity detection and insights into the effects of BGE component

A capillary electrophoresis method integrated with capacitively coupled contactless conductivity detection (CE-C4D) using lactic acid (Lac) (providing background conductivity) and β-alanine (β-Ala) (maintaining stable ionic strength) as the components of background electrolyte (BGE) was developed for the simultaneous determination of eight metal ions (Mg2+, Mn2+, Cd2+, Co2+, Pb2+, Ni2+, Zn2+, Cu2+). The effects of the concentration and composition of BGE and other CE separation conditions in CE-C4D were comprehensively investigated and carefully optimized. It was observed that the optimal BGE consisted 25.0 mmol/L Lac and 25.0 mmol/L β-Ala (at pH 3.6). Under such conditions, all metal ions were successfully separated in less than 10 min. In comparison with two general used BGE systems (2-(N-morpholino) ethanesulfonic acid with histidine, Lac with histidine), the developed BGE has higher sensitivity and better resolution for the certain analytes of Co2+ and Zn2+. Here, the linear ranges of metal ions are within 1.5–3000 μmol/L with high correlation coefficients over 0.994 and the obtained limits of detection (S/N = 3) were in the range of 0.66–8.62 μmol/L. The repeatability with respect to migration times and peak areas, expressed as relative standard deviations, is better than 0.39% and 4.54% (n = 5), respectively. Subsequently, this method was utilized to analyze metal ions in Forsythiae Fructus (FF), a Chinese herbal medicine. The studied recoveries of all metal ions in FF ranged from 82.0% to 103.5%. It was observed that the content of Mg2+ and Mn2+ in FF detected by CE-C4D was similar with that of inductively coupled plasma atomic emission spectrometry (ICP-AES), which demonstrated that the developed CE-C4D had promising in the analysis of metal ions.

Interaction of boron with humic acid and natural organic matter: Experiments and modeling

Boron (B) is highly mobile in the environment. This characteristic easily leads to plant deficiency upon leaching from soil or to toxicity upon accumulation. Boric acid may interact with mineral surfaces as well as natural organic matter. In this study, the boric acid interaction with humic acid (HA) was measured in 0.01 M NaCl and CaCl2 background solutions as a function of pH and the initial B concentration. In the Na-HA suspensions, the free boric acid concentration was determined using a novel approach, applying the Donnan Membrane Technique (DMT) in the dynamic mode. In the method, the experimental rate of diffusion is used as a measure for the free boric acid concentration. B adsorption in Na-HA and Ca-HA systems can be described with the NICA-Donnan model using a single set of boron binding parameters. In Na-HA systems, the adsorption of boric acid strongly increases with the background electrolyte concentration, due to a better screening of the HA charge. In this respect, the adsorption behavior of boric acid is opposite to that of heavy metal ions. Modeling shows that the boric acid adsorption is determined by the competition of H+, Ca2+, and B(OH)3 at binding to the sites of HA. The parameterized NICA-Donnan model is well able to predict the pH-dependent adsorption of boric acid in soil organic horizons. The model is a promising tool for future predictions of the fate of boric acid in a variety of natural multicomponent environments, including soil and seawater.

Kinetic study of humic acid adsorption onto smectite: The role of individual and blend background electrolyte

Many factors can affect the natural organic matter adsorption on clay, such as pH and ionic strength. Blended background electrolyte could be causing better simulation to natural effects. Therefore, kinetic study of humic acid (HA) adsorption onto smectite has been studied under various conditions. Impact of pH and individual and blend background electrolyte with different ionic strength concentration on the rate of adsorption has been investigated. The rate and amount of adsorbed HA on smectite improved with raised background electrolyte concentration, declining pH, and in existence Ca2+. The rate of adsorption order was in the presence of CaCl2 > blend (CaCl2 and KCl) > KCl. The adsorption isotherm was L-shap in the presence of CaCl2 and KCl while was S-shap in presence blend (CaCl2 and KCl). Moreover, the data revealed that the adsorption behavior of HA might be pronounced more obviously by Freundlich model than Langmuir. Two kinetic models were applied to assess the rate constants and kinetic data. The results clarified that HA adsorption on smectite was following to pseudo second order model under various conditions.

Adsorption Efficiency of Anatase TiO2 Nanoparticles Against Cadmium Ions

The anatase TiO2 nanoparticles were synthesized by the reduction of titanium isopropoxide at pH 4.5. The surface area, pore size and pore volume were found to be 156.9 m2/g, 18.23 A and 0.071 cm3/g respectively. The crystallite size calculated by Debye Sherrer’s equation was found 8.1 nm. The percent purity and the composition were studied by energy dispersive X-rays spectroscopy. The point of zero charge has been calculated from salt addition method. The point of zero charge (PZC) was calculated by salt addition method. The PZC was found to shift to higher values by increasing the concentration of background electrolyte. Batch adsorption technique has been employed for the sorption of Cd2+ ions. The adsorption data was found well fitted to Langmuir model. It was observed that the exchange of surface H+ with Cd2+ is greatly affected with temperature. A set of equations was applied to determine the possible adsorption mechanism of Cd2+ ions onto TiO2 surface.

High-Affinity Detection and Capture of Heavy Metal Contaminants using Block Polymer Composite Membranes.

Adsorptive membranes offer one possible solution to the challenge of removing and recovering heavy metal ion contaminants and resources from water supplies. However, current membrane-based sorbents suffer from low binding affinities, leading to issues when contaminants are present at trace concentrations or when the source waters have a high concentration of background electrolytes that compete for open binding sites. Here, these challenges are addressed in the design of a highly permeable (i.e., permeability of ∼2.8 × 104 L m–2 h–1 bar–1) sorbent platform based on polysulfone and polystyrene-b-poly(acrylic acid) composite membranes. The membranes possess a fully interconnected network of poly(acrylic acid)-lined pores, which enables the surface chemistry to be tailored through sequential attachment of polyethylenimine brushes and metal-binding terpyridine ligands. The polyethylenimine brushes increase the saturation capacity, while the addition of terpyridine enables high-affinity binding to a diversity of transition metal ions (i.e., Pd2+, Cd2+, Hg2+, Pb2+, Zn2+, Co2+, Ni2+, Fe2+, Nd3+, and Sm3+). This platform removes these metal contaminants from solution with a sorbent capacity of 1.2 mmol g–1 [based on Cu2+ uptake]. The metal capture performance of the functionalized membranes persists in spite of high concentrations of competitive ions, with >99% removal of Pb2+ and Cd2+ ions from artificial groundwater and seawater solutions. Breakthrough experiments demonstrate the efficient purification of feed solutions containing multiple heavy metal ions under dynamic flow conditions. Finally, fluorescence quenching of the terpyridine moiety upon metal ion complexation offers an in situ probe to monitor the extent of sorbent saturation with a Stern–Volmer association constant of 2.9 × 104 L mol–1. The permeability, capacity, and affinity of these membranes, with high-density display of a metal-binding ligand, offer a chemically tailored platform to address the challenges that arise in ensuring clean water.

Carbonate Dissolution Mechanisms in the Presence of Electrolytes Revealed by Grand Canonical and Kinetic Monte Carlo Modeling

Dissolution of carbonate minerals is a complex multistep process, characterized by the particular sequence of steps dependent on pH and background electrolyte concentration. Currently, available di...