Background Ions Research Articles

Effect of background ions and physicochemical factors on the cotransport of microplastics with Cu2+ in saturated porous media

Microplastics (MPs) in subsurface environments are migratory and can carry heavy metals, increasing the extent of MP and heavy metal pollution. This study used quartz sand-filled column experiments to investigate the adsorption and cotransport behaviours of PS-MPs, O3, UV-aged PS-MPs, and Cu2+ at different MP concentrations, ionic strengths, and ionic valences in a saturated porous medium. The results showed that when MPs migrate alone in the absence of an ionic background, higher concentrations have increased mobility. In contrast, an increase in the background ion concentration or ion valence inhibits the individual transport capacity of PS-MPs. An increase in the concentration of background ions or elevation in the valence state promotes Cu2+ transport because of the action of the double electric layer on the surface of the colloid and the electrostatic repulsive forces combined with the background ions. The adsorption capacity of aged PS-MPs was stronger than that of PS-MPs because of the binding of the aged PS-MPs to Cu2+ through complexation and electrostatic attraction. In the binary system of PS-MPs/Cu2+, PS-MPs promoted Cu2+ transport and the mobility of Cu2+ loaded by PS-MPs decreased with increasing background ion concentration. The cotransport results showed that MPs promote Cu2+ transport in the following order: O3-aged Ps > UV-aged Ps > Ps, as the increasing cation concentration in the MPs and Cu2+ occupies the PS surface adsorption sites. Overall, PS is an effective carrier for Cu2+. These findings offer fresh exploration concepts for the joint migration of MPs and heavy metals in underground settings.

Interaction of driven ``cold'' electron plasma wave with thermal bulk via ion spatial inhomogeneity

Abstract Using high resolution Vlasov - Poisson simulations, evolution of driven ``cold" electron plasma wave (EPW) in the presence of stationary inhomogeneous background of ions is studied. Mode coupling dynamics between ``cold'' EPW with phase velocity $v_{\phi}$ greater than thermal velocity i.e $v_{\phi} \gg v_{thermal}$ and its inhomogeneity induced sidebands is illustrated as an initial value problem. In driven cases, formation of BGK like phase space structures corresponding to sideband modes due to energy exchange from primary mode to bulk particles via wave-wave and wave-particle interactions leading to particle trapping is demonstrated for inhomogeneous plasma. Qualitative comparison studies between initial value perturbation and driven problem is presented, which examines the relative difference in energy transfer time between the interacting modes. Effect of variation in background ion inhomogeneity amplitude as well as ion inhomogeneity scale length on the driven EPWs is reported.

High-resolution acoustic ejection mass spectrometry for high-throughput library screening

An approach is described for high-throughput quality assessment of drug candidate libraries using high-resolution acoustic ejection mass spectrometry (AEMS). Sample introduction from 1536-well plates is demonstrated for this application using 2.5 nL acoustically dispensed sample droplets into an Open Port Interface (OPI) with pneumatically assisted electrospray ionization at a rate of one second per sample. Both positive and negative ionization are shown to be essential to extend the compound coverage of this protease inhibitor-focused library. Specialized software for efficiently interpreting this data in 1536-well format is presented. A new high-throughput method for quantifying the concentration of the components (HTQuant) is proposed that neither requires adding an internal standard to each well nor further encumbers the high-throughput workflow. This approach for quantitation requires highly reproducible peak areas, which is shown to be consistent within 4.4 % CV for a 1536-well plate analysis. An approach for troubleshooting the workflow based on the background ion current signal is also presented. The AEMS data is compared to the industry standard LC/PDA/ELSD/MS approach and shows similar coverage but at 180-fold greater throughput. Despite the same ionization process, both methods confirmed the presence of a small percentage of compounds in wells that the other did not. The data for this relatively small, focused library is compared to a larger, more chemically diverse library to indicate that this approach can be more generally applied beyond this single case study. This capability is particularly timely considering the growing implementation of artificial intelligence strategies that require the input of large amounts of high-quality data to formulate predictions relevant to the drug discovery process. The molecular structures of the 872-compound library analyzed here are included to begin the process of correlating molecular structures with ionization efficiency and other parameters as an initial step in this direction.

Stratified nanoflower bimetallic cobalt/iron alloy derived from CoFe-MOFs as efficient peroxymonosulfate activator for antibiotics degradation: Performance, mechanism, and toxicity

Co-based metal-organic framework (Co-MOFs) derivative has gained wide attention in the field of advanced oxidative processes (AOPs). However, the degradation efficiency of single cobalt element remains suboptimal and its activation mechanism still needs to be further explored. In this study, stratified nanoflower bimetallic cobalt/iron alloys (CoFe-NC), derived from cobalt/iron bimetallic-organic frameworks (CoFe-MOFs), was synthesized via self-assembly at room temperature, hydrothermal synthesis and high-temperature carbonization processes and their performance as efficient activators of peroxymonosulfate (PMS) for the degradation of antibiotics was evaluated (removal efficiency of 100 % within 40 min, k=0.0951 min−1). The excellent degradation property benefit by specific nano-flowers structure with high specific surface area (424.67 m2/g), the cycle between Co0→Co2+↔ Co3+ and Fe0→Fe2+↔Fe3+, synergistic effect of Co and Fe bimetals. Furthermore, the CoFe-NC/PMS system exhibits exceptionally high cyclic stability (over 85 % degradation efficiency after four times degradation), a wide range of pH (3−11) and resistance to background ion interference (Cl–, H2PO4–, NO3–, HCO3– and HA), and reduced toxicity of the degradation products. Degradation mechanistic studies demonstrated that the activation of PMS by CoFe-NC generated amounts of reactive oxygen species (ROS) (SO4•−, •OH, •O2− and 1O2). Additionally, high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis identified fifteen intermediate degradation products and three possible degradation pathways were proposed. The results highlight the potential of CoFe-NC as a catalyst for antibiotic removal, providing insights into the optimization of bimetallic-organic framework for environmental applications.

Thermodynamic Modeling of the Composition of the Main Background Ions and Determination of Gas-Kinetic Temperature in the Normal (“Hot”) Inductively Coupled Plasma

Thermodynamic Modeling of the Composition of the Main Background Ions and Determination of Gas-Kinetic Temperature in the Normal (“Hot”) Inductively Coupled Plasma

Plasma opacity induced by laser-driven movement of background ions

Abstract The transition threshold from relativistically transparent regime to opaque regime in the interaction of an ultra-intense laser pulse and a bulk plasma with mobile background ions is investigated. The threshold corresponds to the onset of laser hole-boring. We show that for an ultra-intense laser, the threshold depends on the ion composition of the plasma, and the corresponding plasma density is significantly lower than that with ion immobile plasma. These are supported by 1D PIC simulations by using hydrogen plasma and fully ionized carbon plasma. The movement of background ions modifies the dynamics and distribution of electrons in the plasma, which results in the Doppler-red-shift of the incident laser and the increase of the effective plasma density. An intuitive model, which gives the dependence of the transparency-opaqueness threshold on laser intensity and frequency, as well as the ion composition, is established. It is tested by multi-dimensional PIC simulations with hydrogen plasma.

Magnetosonic Waves Excited by Maxwellian Ring Protons in Space Plasma Environment

A comprehensive theoretical model for a homogeneous plasma system of hot, tenuous Maxwellian ring-distributed protons and the cold background of Maxwellian ions and electrons is used to study the resonant instabilities of magnetosonic (MS) waves. The perpendicular velocity integrals associated with the Maxwellian ring distribution have no analytical solution, hence, are solved numerically, while the parallel velocity integrals are solved analytically by invoking series expansion of the plasma dispersion function. For the plasma parameters relevant to Earth’s inner magnetosphere, the theoretical model generates MS waves with frequencies from 5 times the local proton cyclotron frequency to above the lower hybrid frequency for a propagation angle of 89.5°. Hydrogen (H+) band electromagnetic ion cyclotron waves are also excited by the Maxwellian ring protons for the same set of plasma parameters. A detailed analysis reveals that a sufficiently large ring velocity, as well as a smaller perpendicular and parallel thermal velocity, can enhance the MS wave growth. The study also explores the role of background plasma parameters in modulating the waves. The present theoretical model reproduces the harmonics of the MS waves observed by the Van Allen Probes in the Earth’s inner magnetosphere. Further, the model can generate MS waves in other plasma environments, e.g., Mars, where the presence of ring protons has been established by MAVEN in connection with the MS wave observations.

Electrothermal filamentation of igniting plasmas.

Dense, hot plasmas are susceptible to the electrothermal instability: a collisional process which permits temperature perturbations in electron currents to grow. It is shown here that linearizing a system comprised of two opposing currents and a mobile ion background as three distinct fluids yields unstable modes with rapid growth rates (∼10^{13}s^{-1}) for wavenumbers below a threshold k_{th}. An analytical threshold condition is derived, this being surpassed for typical hot-spot and shell parameters. Particle-in-cell simulations successfully benchmark the predicted growth rates and threshold behavior. Electrothermal filamentation within the shell will impact the burn wave propagation into the cold fuel and resulting burn dynamics.

Effect of adiabatic trapping of electrons on the nonlinear evolution of ion temperature gradient driven drift mode in a dispersive plasma

We have theoretically investigated the effect of adiabatic trapping of electrons on ion temperature gradient (ITG) driven nonlinear drift mode in a warm and dispersive electron-ion plasma. For this purpose, we have incorporated the gradients in the background plasma density, ion temperature and ambient magnetic field and derived two different nonlinear partial differential equations (NLPDEs). One of them contains only fractional nonlinearity while the other one incorporates the effect of both quadratic and fractional nonlinearities. We have obtained the exact solutions of these NLPDEs by using the functional variable method. We have used the graphical analysis to carry out the parametric study of the obtained solutions for the Tokamak plasma parameters. We have shown that the amplitude and the width of these nonlinear structures depend on the plasma parameters like T e , T i and η i . This work may be helpful to understand the effect of electron trapping on the low frequency drift type modes in laboratory and space plasmas.

Interfacial effect of coexisting salt cations on extraction of erbium using gas bubble-supported organic liquid membrane

The conventional understanding about the specific ion effect from the coexisting electrolyte salts on the extraction and separation of target metal ions during liquid-liquid solvent extraction cannot explain some abnormal phenomena when more than one kind of background ions coexisting in the aqueous feed solutions to be separated. In this work, the specific ion effect of coexisting ions, Mg2+ and Al3+ as the example here, on extraction of Er3+ ion was investigated using gas bubble-supported organic liquid membrane. A very interesting phenomenon was noticed that, the difference in Er3+ extraction percentage was only 11.7 % in the Er-Mg solution system with addition of Al3+ ions or not, while it could reach 18.0 % in that of Er-Al with addition of Mg2+ ions or not. When Mg2+ and Al3+ coexisted simultaneously in the feed solutions, their specific ion effect on improving the extraction percentage of Er3+ was not equal to the sum of that when only single Mg2+ or Al3+ exists, respectively. Furthermore, a thinner organic liquid membrane supported by gas bubbles was in favor of enhanced interfacial enrichment of Er3+ and its diffusion mass transfer near the interface. During gas bubble-supported organic liquid membrane extraction, Mg2+ ions exhibited more obvious specific ion effect due to a weaker interaction with P507 molecules. However, a stronger hydration ability of Al3+ than Mg2+ ions induces a stronger competition of Al3+ with P507 molecules. Therefore, the coexistence of Mg2+ and Al3+ ions could play a synergistic role in enhancing enrichment of Er3+ on the basis of the mutual interference from the synergistic specific ion effect of coexisting Al3+ and Mg2+ ions. The research helps thoroughly understand the regulation mechanism on the synergistic specific ion effect for selective extraction of specified ions from the complex solutions containing multiple coexisting background ions.

How Fe-La-CS microspheres have selective adsorption capacity for As(V) over a wide pH range: Coupling molecular scale interpretation with experiments

In this study, an Fe-La-CS adsorbent with a reticulated structure was prepared by an in situ method, which was able to adsorb arsenate efficiently over a wide pH range of 3–11. The incorporation of iron and lanthanum ions broadened the tolerant pH range of the adsorbent compared with chitosan beads (CS). Arsenic was mainly present in the pH range of 3–9 as two forms, H2AsO4− and HAsO42−. Calculations using the density-functional theory (DFT) showed that in the Ligand interactions and electrostatic interactions dominate in the pH range, with surface precipitation, and hydrogen bonding interactions playing a facilitating role. The background ions mainly compete with arsenic adsorption for electrostatic interaction sites. However, due to the different valence states of the background ions, the competition intensity is different. Such as low valence state representative ions Na+, K+ competitiveness is weak, and arsenic competition adsorption first occupy different adsorption sites, therefore, from the quantum chemistry and molecular dynamics point of view of Na+, K+ on arsenic adsorption almost no effect. Cl−, SO42− will have some influence on arsenic adsorption because of the same charge with arsenic, but the charged amount is smaller than arsenic and the molecular structure is different from that of arsenic, so the influence is not very big. In summary, the material design of Fe-La-CS adsorbent has great potential and theoretical significance for selective purification of heavy metal wastewater at wide pH.

The high dust density regime of dusty plasma: Theory and simulations

It is shown that the dust density regimes in the dusty plasma are characterized by two complementary screening processes: (i) the low dust density regime where the Debye screening is the dominant process and (ii) the high dust density regime where the “Coulomb screening” is the dominant process. The Debye regime is characterized by a state where all dust particles carry an equal and constant charge. The high dust density regime or the “Coulomb plasma” regime is characterized by (a) “Coulomb screening” where the dust charge depends on the spatial location and is screened by other dust particles in the vicinity by charge reduction, (b) “asymptotic freedom” where dust particles, which on an average carry minimal electric charge, are asymptotically free in the high dust density limit, (c) uniform dust charge density and plasma potential, (d) dust charge neutralization by a uniform background of hot ions, and (e) dust is weakly coupled due to strong Coulomb screening. Thus, the dusty plasma is essentially a weakly coupled, one-component plasma with screening in the high dust density limit. Molecular dynamics (MD) simulations verify these properties. The MD simulations are performed, using a recently proposed Hamiltonian formalism to study the dynamics of Yukawa particles carrying variable electric charge. A hydrodynamic model for describing the collective properties of Coulomb plasma and its characteristic acoustic mode called the “Coulomb acoustic mode” arising due to imperfect Coulomb screening is given.

Thermodynamic Simulation of the Composition of the Major Background Ions in Low-Temperature (“Cold”) Inductively Coupled Plasma

Thermodynamic Simulation of the Composition of the Major Background Ions in Low-Temperature (“Cold”) Inductively Coupled Plasma

Electron acoustic solitary waves in relativistically quantum magnetoplasmas with electron exchange correlation effects

The propagating of electron acoustic solitary waves (EASWs) in relativistically magnetized quantum plasmas which consists inertial cold electrons, inertialess hot electrons and stationary background ions have been theoretically investigated. The modified Zakharov-Kuznetsov (ZK) equation is derived by adopting the standard reductive perturbation method to describe the nonlinear evolution of the EASWs. After discussing the effects of various parameter values on the solitary structures, it is shown that the solitary structures are very sensitive to the relativistic degeneracy effect, the cold to hot electrons number density ratio and the electron exchange correlation effects. The numerical analysis can be well described by the existing analytical theory. Our results may be useful in explaining the physics behind the formation of the EASWs in both astrophysical and laboratory plasmas.

The response of the cometary ionosphere to space weather forcing

ABSTRACT The Rosetta spacecraft observed the temporal evolution of the ion populations within the ionosphere of comet 67P/Churyumov–Gerasimenko. A striking feature of the ion spectrum is represented by the so-called medium-energy ion peaks, which recurrently emerge from the low-energy ion background with their energy levels typically reaching 50 to 1000 eV before their energy gradually decreases, and they disappear from the measurements. These peaks are believed to be caused by space weather forcing, but there was no conclusive evidence until now. We investigated the characteristics of these ions, paying special attention to the connection between the solar wind dynamic pressure and the amount and energy of the medium-energy ions. Our findings reveal a strikingly accurate direct correlation between the dynamic pressure of the solar wind at the position of the comet and the amount of medium-energy ions measured by Rosetta. The ion energy also unquestionably reacts to the effects of solar wind pressure variation, but this parameter is strongly affected by the production rate and the distance from the nucleus as well. We explain these close correlations between cometary ion and solar wind characteristics using the well-founded assumption that certain boundary layers of the magnetosphere can move in and out under the influence of higher and lower solar wind pressure.

Characteristics and transformations of dust acoustic double-layers in plasmas with adiabatically trapped-nonextensive ions using Tsallis-Gurevich distribution

The investigation focuses on examining the characteristics of dust acoustic double-layers (DA-DLs) in the presence of adiabatically trapped-nonextensive ions featuring Tsallis-Gurevich distribution. Indeed, the ion-density and pseudo-potential expressions are formulated in terms of transcendental functions, allowing for a detailed analysis of Dust Acoustic Double Layers associated with complex plasmas in the presence of non-extensive adiabatically trapped ions. The study then delves into the impact of background ion nonextensivity on key DA-DLs properties. The findings reveal that our plasma model can exhibits both compressive and rarefactive DA-DLs, depending on the nonextensive parameter q. Also, the results indicate that in both sub-sonic and supra-sonic scenarios, the amplitude of the DA-DLs structure rises as the nonextensive parameter decreases. Additionally, it is observed that, for a constant value of the nonextensive parameter q, the amplitude of the DA-DLs structure increases with higher Mach numbers. This investigation, prompted by observations in space and laboratory plasmas containing non-Maxwellian particles alongside trapped particles, has the potential to complement and offer fresh insights into previous works on solitary waves in plasma.

Removal of trivalent chromium ions in model contaminated groundwater using hexagonal boron nitride as an adsorbent

The feasibility of using hexagonal boron nitride (h-BN) to treat heavy metal Cr(III) from model contaminated groundwater was evaluated in this study by adsorption experiments and characterizations. To the best of our knowledge, this study is the first attempt to conduct the adsorption of Cr(III) by h-BN under various experimental conditions such as exposure time, ratio of adsorbates and adsorbents, solution pH, background ions with different ionic strength, and the presence of humic acids (HA) in model contaminated groundwater. The optimized h-BN showed excellent maximum adsorption capacity (i.e., 177 mg ∙ g−1) when the concentrations of Cr(III) and h-BN were 10 and 10 mg ∙ L−1, respectively. Subsequently, we confirmed there was a negligible change in the adsorption performance of Cr(III) by h-BN in the presence of co-ions (i.e., K and Mg) in concentrations in a range from 50 to 1000 mg ∙ L−1. Furthermore, the adsorption performance of Cr(III) gradually improved with HA concentrations from 2.5 to 25 mg ∙ L−1. Interestingly, the maximum adsorption performance of Cr(III) by both HA and h-BN increased until 500 mg ∙ g−1 in the presence of 25 mg ∙ L−1 HA. The adsorption mechanism was clarified by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Additionally, we successfully confirmed that h-BN could be reused until five cycles. On the basis of the adsorption performance results and characterizations, h-BN can be utilized as an efficient and practical adsorbent to treat Cr(III) in groundwater treatment.

Salt gradient enhanced sensitivity in nanopores for intracellular calcium ion detection

Intracellular calcium ion detection is of great significance for understanding the cell metabolism and signaling pathways. Most of the current ionic sensors either face the size issue or sensitivity limit for the intracellular solution with high background ion concentrations. In this paper, we proposed a calmodulin (CaM) functionalized nanopore for sensitive and selective Ca2+ detection inside living cells. A salt gradient was created when the nanopore sensor filled with a low concentration electrolyte was in contact with a high background concentration solution, which enhanced the surface charge-based detection sensitivity. The nanopore sensor showed a 10 × sensitivity enhancement by application of a 100-fold salt gradient, and a detection limit of sub nM. The sensor had a wide detection range from 1 nM to 1 mM, and allowed for quick calcium ion quantification in a few seconds. The sensor was demonstrated for intracellular Ca2+ detection in A549 cells in response to ionomycin.

Biochar-Supported FeCo-MOF derivative catalyzes PDS-Mediated degradation of tetracycline

Bimetallic metal–organic framework (MOF) has gained wide attention in the field of advanced oxidative processes (AOPs), however, the agglomeration problem severely limits its active sites and its activation mechanism still needs to be further explored. This study developed the BC@CoFe composite material, utilizing biochar (BC) to support FeCo-MOF derivatives, effectively alleviating their agglomeration and structural collapse. The results of the BC@CoFe activated peroxydisulfate (PDS) system for the degradation of tetracycline (TC) revealed an excellent degradation efficiency up to 97.7 % in 2 h for TC solution (20 mg/L, degradation rate constants k = 7.066 mM-1min−1). Furthermore, the BC@CoFe/PDS system exhibits exceptionally high cyclic stability (73.23 % degradation efficiency after 12 h continuous degradation), a wide range of pH (3–11) and temperature tolerance (20-60℃), resistance to background ion interference (SO42-, H2PO4-, NO3– and HA), and reduced toxicity of the degradation products. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) analyses show that the exceptional catalytic performance of BC@CoFe primarily stems from the synergistic effect between Fe(II)/Co(III) and Fe(III)/Co(II). Regarding the reactive active species involved in TC degradation, the contribution rates of 1O2, SO4•- and ·OH were measured and calculated to be 73.6 %, 14.9 %, and 11.5 %, respectively. Thus, the BC@CoFe/PDS system exhibits outstanding catalytic activity and has broad practical applications in water treatment.

Phenotypic and genomic characterization of Methanothermobacter wolfeii strain BSEL, a CO2-capturing archaeon with minimal nutrient requirements.

A new variant of Methanothermobacter wolfeii was isolated from an anaerobic digester using enrichment cultivation in anaerobic conditions. The new isolate was taxonomically identified via 16S rRNA gene sequencing and tagged as M. wolfeii BSEL. The whole genome of the new variant was sequenced and de novo assembled. Genomic variations between the BSEL strain and the type strain were discovered, suggesting evolutionary adaptations of the BSEL strain that conferred advantages while growing under a low concentration of nutrients. M. wolfeii BSEL displayed the highest specific growth rate ever reported for the wolfeii species (0.27 ± 0.03 h-1) using carbon dioxide (CO2) as unique carbon source and hydrogen (H2) as electron donor. M. wolfeii BSEL grew at this rate in an environment with ammonium (NH4+) as sole nitrogen source. The minerals content required to cultivate the BSEL strain was relatively low and resembled the ionic background of tap water without mineral supplements. Optimum growth rate for the new isolate was observed at 64°C and pH 8.3. In this work, it was shown that wastewater from a wastewater treatment facility can be used as a low-cost alternative medium to cultivate M. wolfeii BSEL. Continuous gas fermentation fed with a synthetic biogas mimic along with H2 in a bubble column bioreactor using M. wolfeii BSEL as biocatalyst resulted in a CO2 conversion efficiency of 97% and a final methane (CH4) titer of 98.5%v, demonstrating the ability of the new strain for upgrading biogas to renewable natural gas.IMPORTANCEAs a methanogenic archaeon, Methanothermobacter wolfeii uses CO2 as electron acceptor, producing CH4 as final product. The metabolism of M. wolfeii can be harnessed to capture CO2 from industrial emissions, besides producing a drop-in renewable biofuel to substitute fossil natural gas. If used as biocatalyst in new-generation CO2 sequestration processes, M. wolfeii has the potential to accelerate the decarbonization of the energy generation sector, which is the biggest contributor of CO2 emissions worldwide. Nonetheless, the development of CO2 sequestration archaeal-based biotechnology is still limited by an uncertainty in the requirements to cultivate methanogenic archaea and the unknown longevity of archaeal cultures. In this study, we report the adaptation, isolation, and phenotypic characterization of a novel variant of M. wolfeii, which is capable of maximum growth with minimal nutrients input. Our findings demonstrate the potential of this variant for the production of renewable natural gas, paving the way for the development of more efficient and sustainable CO2 sequestration processes.