Bipolar Ion Research Articles

Bipolar ionization-mediated airborne virus inactivation and deposition rates

Bipolar ionization (BPI) of indoor air has emerged as a widely implemented bulk-air disinfection technology to reduce human exposure to airborne viruses. This study presents BPI-mediated decay rate constants for the inactivation and deposition of infectious viral aerosols. Rate constants are estimated for the enveloped bacteriophage Ф6, a common SARS-CoV-2 surrogate, at low (∼25 %), medium (∼50 %) and high (∼75 %) relative humidity (RH) levels under bipolar ion concentrations of 106 ions/cm3. Enhanced BPI-facilitated viral inactivation rate constants of 4.6, 6.9, and 7.6 h −1 under low, middle, and high RH, respectively, are reported. BPI-mediated infectious decay and deposition rates for aerosolized Ф6 were RH-dependent, with significant increases from low to high RH (p < 0.05). Calculated BPI susceptibility constants, that account for ion concentrations, reveal limited airborne viral inactivation (<0.1 h −1) at bipolar ion levels (103 ions/cm3) that are common in bulk air where BPI is applied.

HVE ion sources for medium and high-energy accelerator systems

Since decades, High Voltage Engineering (HVE) manufactures particle accelerator systems for research and industry. HVE’s product line includes Singletron and Tandetron accelerator systems with terminal voltages of up to 6 MV. They are dedicated to a wide range of applications including ion implantation and irradiation, Ion Beam Analysis (IBA), Accelerator Mass Spectrometry (AMS), and neutron reference fields. In this paper, we give an overview of the different positive and negative ion sources that are applied in these systems. We focus especially on the recent development and the performance of a compact 2.45 GHz permanent magnet ECR bipolar ion source (HVE Model SO-160), used for negative light-ion injection into tandem accelerators. It generates high-current, low-emittance light-ion beams at 30 keV energy. The novelty in the design of this ion source is that it combines direct negative extraction for H − with positive extraction for He + that is followed by charge exchange to He − in a Na-based electron donor canal. The source produces in excess of 250 eµA of H − and more than 20 eµA of He −. It is expected the design allows for substantially higher currents, especially for H −.

Bipolar ionization rapidly inactivates real-world, airborne concentrations of infective respiratory viruses.

The SARS-CoV-2 (COVID-19) pandemic has highlighted the urgent need for strategies that rapidly inactivate airborne respiratory viruses and break the transmission cycle of indoor spaces. Air ions can reduce viable bacteria, mold, and virus counts, however, most studies use small test enclosures with target microbes and ion sources in close vicinity. To evaluate ion performance in real-world spaces, experiments were conducted in a large, room-size BSL-3 Chamber. Negative and positive ions were delivered simultaneously using a commercially available bipolar air ion device. The device housed Needle Point Bipolar ionization (NPBI) technology. Large chamber studies often use unrealistically high virus concentrations to ensure measurable virus is present at the trial end. However, excessively high viral concentrations bias air cleaning devices towards underperformance. Hence, devices that provide a substantial impact for protecting occupants in real-world spaces with real-world virus concentrations are often dismissed as poor performers. Herein, both real-world and excessive virus concentrations were studied using Influenza A and B, Human Respiratory Syncytial Virus (RSV), and the SARS-CoV-2 Alpha and Delta strains. The average ion concentrations ranged from 4,100 to 24,000 per polarity over 60-minute and 30-minute time trials. The reduction rate was considerably greater for trials that used real-world virus concentrations, reducing infectivity for Influenza A and B, RSV, and SARS-CoV-2 Delta by 88.3-99.98% in 30 minutes, whereas trials using in-excess concentrations showed 49.5-61.2% in 30 minutes. These findings strongly support the addition of NPBI ion technology to building management strategies aimed to protect occupants from contracting and spreading infective respiratory viruses indoors.

Simultaneous observations of atmospheric vertical potential gradient from coastal Antarctic stations Bharati and Maitri

Simultaneous observations of the atmospheric electric potential gradient (PG) at Bharati and Maitri stations were studied from 2014 to 2016. A new regional diurnal pattern of fair-weather PG for the coastal Antarctic region, perhaps the ubiquitous characteristics of the PG for the coastal Antarctic region, has been identified. This pattern has a significant broad minimum around noon hours. It is around this time the wind speed is also maximum. The PG data of past years of Syowa, Vostok, and Carnegie Cruise were also used in this study. The surface wind distorts the fair-weather diurnal pattern of PG over Bharati more intensely than at Maitri. The katabatic wind effect on the PG at Bharati appears to be more intense than at Maitri. The topography and katabatic winds associated with the Lambert glacier could be the reason. The observation of Bipolar Air Ion Concentration (BAIC) suggests that the wind speed significantly affects the concentration by accumulation and dispersion. The concentration is maximum when the wind speed is minimum. As the air ion concentration controls the conductivity, the PG is expected to be minimum during these hours to produce an anomalous diurnal pattern in the PG at Bharati. Data quality is improved by measuring the PG with a field monitor at the surface level instead of at an elevated position. This study provides new hope in pursuing globally representative data of the PG for further investigations on the global thunderstorm activity and the solar-terrestrial weather relationship.

Investigation of the effect of impurity concentration in the simulated industrial saline water on the scaling phenomenon on ion exchange membranes

One of the most critical problems to be solved in membrane separation processes is the fouling of membranes. Fouling causes a reduction in current efficiency in processes using ion-exchange membranes. In this study, the mechanism of fouling on the anion exchange membrane, cation exchange membrane, and bipolar membranes caused by impurities such as CaCl2, MgCl2, Na2CO3, and NaHCO3 in the electrodialysis process of the feed solution containing NH4Cl and NaCl as the main components were investigated. The effects of initial impurity concentration on bipolar membrane electrodialysis stack resistance, demineralization, ion flux, acid and base conversion, and concentration of produced acid and base were investigated. SEM-EDX, XRD, FTIR, and TGA analyses were used for membrane characterization. Chemical cleaning was done to remove impurities in the membrane and spacer structure. The effects of chemical cleaning on cell performance were determined by comparing the process performances before and after cleaning. Experimental results showed that ions such as Ca2+ and Mg2+ in the feed solution cause precipitate on the cation exchange membrane and spacers in the base compartment. The results revealed that these precipitates do not cause structural damage to the membranes but affect their performance.

Dielectric barrier discharge as bipolar ion source for aerosol charging: Application to filtration, thin film, and aerosol size measurement

We have investigated the potentialities of dielectric barrier discharges (DBD) for aerosol electro-processing with a special focus on ion production and aerosol charging for deposition (filtration and materials) and aerosol measurement tools. The advantages and drawbacks of aerosol injection downstream or upstream of the discharge are compared according to the application. The main parameters that control ion production and transport are investigated based on post-discharge ion current measurements. Post-DBD aerosol chargers are compared for submicron particle size measurements based on aerosol bipolar charging and electrical mobility analysis. Finally, the principle of counterflow extraction of bipolar ion from an atmospheric pressure DBD is established from upstream measurements of positive and negative ion fluxes in air, without neither ozone (<0.1 ppmv) nor nanoparticles.

A numerical study on desalination performance enhancement by bipolar ionic diode nanochannels

Bio-inspired ion diodes constructed by asymmetric charged (bipolar) nanochannels have shown outstanding performance in ion transport control which are promising candidates for the development of high-performance water desalination systems. However, understanding of seawater desalination by ionic diode nanochannels is still very limited. This paper uses a numerical model coupling Poisson-Nernest-Planck and Navier-Stokes equations to systematically investigate the desalination behavior of bipolar ion diodes. The effects of nanochannel structure including channel length, diameter, charge polarity, properties of working fluids, and external pressure on the ion rejection efficiency are investigated. The results show that under optimal conditions, the bipolar channel can produce better ion rejection compared to the unipolar channel due to its excellent ion transport control performance, a bipolar ion diode-based desalination system can produce 20 % higher ion rejection rates compared to that of a unipolar channel system. In particular, an external voltage applied to the system is able to further enhance the ion rejection performance of the bipolar channel by more than 27 % compared to that of the case without applied voltage. This work systematically reveals the working mechanism of enhancing water desalination performance by bio-inspired ion diodes and provides a new route for the development of high-efficiency desalination plants.

Tribochemical investigation of Cr-doped diamond-like carbon with a MoDTC-containing engine oil under boundary lubricated condition

Cr-doped diamond-like carbon (Cr-DLC) coatings were deposited and investigated for their tribological properties. A hybridized deposition technique consisted of a bipolar plasma-based ion implantation and deposition (PBII&D) and magnetron sputtering was used for the deposition. Raman spectra revealed an increase of ID/IG upon the Cr introduction, indicating the embedded CrCx act as catalysts to produce sp2 sites. The coefficients of friction (COF) were effectively reduced once MoDTC was added to the base oil. X-ray photoelectron spectroscopy (XPS) confirmed the presence of MoO3, MoS2, and MoS2−xOx in the MoDTC-derived tribofilm. The contribution of MoS2−xOx decreased with the Cr content, suggesting that the wear particles of CrCx intervenes in the process of MoDTC decomposition by preventing the oxidation of MoS2 sheets.

Chromium-Modified Heterogeneous Bipolar Membrane: Structure, Characteristics, and Practical Application in Electrodialysis.

The modification of an MB-2 bipolar ion exchange membrane with chromium (III) hydroxide was carried out by a chemical method, namely, by the sequential treatment of the membrane with a solution of chromium (III) salt and alkali. Data on the morphology, phase, and chemical composition of the modified membrane were obtained using scanning electron microscopy and energy-dispersive analysis. In particular, it was shown that the modifier was distributed in a layer 30-50 microns thick at the boundary of the cation- and anion-exchange layers of the bipolar membrane. The electrochemical behavior of the modified membrane in the process of sodium sulfate conversion was studied by measurements of the following characteristics: the current efficiency of the acid and base, the energy consumption of the process, and the degree of contamination of the target products with salt ions. It was shown that the resulting membrane has an alkali and acid yield of 61% and 57%, respectively. This is higher than the same yields for the industrial unmodified MB-2 membrane (38% and 30%). The results of this study demonstrated that the modified samples allowed obtaining a higher yield of acid and base, reducing the content of salt ions in the target products and also reducing the electricity consumption for obtaining a unit of the target product. The concentration dependences of the electrical conductivity of the MK-40 heterogeneous ion-exchange membrane, which is a cation-exchange layer of MB-2, in sodium sulfate solutions before and after its modification with chromium (III) oxide were obtained. A decrease in the specific electrical conductivity of the membrane with the introduction of a modifier was established. A quantitative assessment of the influence of the modifier on the current flow, volume fraction, and spatial orientation of the conductive phases of MK-40 was carried out using an extended three-wire model for the description of the model parameters of ion-exchange materials. When a modifying additive was introduced into MK-40, the fraction of the current passing through the inner solution and the intergel phase decreased. This was due to the substitution of part of the free solution in the pore volume by the modifier. A variant of the practical application of electrodialysis with the chromium-modified bipolar ion-exchange membranes is recommended.

Detection of current-sheet and bipolar ion flows in a self-generated antiparallel magnetic field of laser-produced plasmas for magnetic reconnection research.

Magnetic reconnection in laser-produced magnetized plasma is investigated by using optical diagnostics. The magnetic field is generated via the Biermann battery effect, and the inversely directed magnetic field lines interact with each other. It is shown by self-emission measurement that two colliding plasmas stagnate on a midplane, forming two planar dense regions, and that they interact later in time. Laser Thomson scattering spectra are distorted in the direction of the self-generated magnetic field, indicating asymmetric ion velocity distribution and plasma acceleration. In addition, the spectra perpendicular to the magnetic field show different peak intensity, suggesting an electron current formation. These results are interpreted as magnetic field dissipation, reconnection, and outflow acceleration. Two-directional laser Thomson scattering is, as discussed here, a powerful tool for the investigation of microphysics in the reconnection region.

Influence of location junction on ion transfer behavior in conical nanopores with bipolar polyelectrolyte brushes

A bipolar ion diode consists of two positively and negatively charged surfaces that show the distribution of specific ions under different applied voltages. One of the most important electrokinetic phenomena occurring in bipolar nanopores is ionic current rectification (ICR). ICR in nanopores occur when, by applying a voltage to both ends of a nanochannel, the system exhibits non-linear current-voltage behavior or diode-like behavior, in other words, ionic current occurs in a specific direction. In modeling bipolar soft nanochannels, it is usually assumed that the properties of the soft layer and the electrolyte are the same, which is not true for soft layers with high charge densities. In the present work, the effect of sharp and wide aperture radius of nanochannels on ionic current rectification in bipolar nanochannels by coating polyelectrolytic layer with conical geometry in different values of soft layer lengths was studied. For this purpose, by adopting a numerical calculation approach Finite element, Poisson-Nernst-Planck and Navier-Stokes equations were solved for steady-state by considering different permeability values, diffusion coefficient, and dynamic viscosity for polyelectrolyte and electrolyte In general, it can be concluded that the bipolar conical nanopore has a higher ICR than the cylinder geometry with the same average radius If the junction is at the tip of the nanopore. For example, when the mole concentration was equal to c0=50mM, the ICR for the bipolar conical nanopore with a soft layer with an optimal junction at the tip of the nanopore reached 45, while in the bipolar cylindrical nanopore at best (the optimal junction in the middle of the nanopore) reached 25.

Charging and dynamics of polystyrene latex aerosols under bipolar and unipolar ion field–ELPI measurements and comparison with charging theories

The nuclear reactor research community is interested in charged aerosol dynamics in a confined environment. Various aerosol charging theories described for bipolar and unipolar ion field exposures are reviewed using experimental measurements with PSL aerosols and ELPI. The (n+/n-) ratio of bipolar ions marginally increases as more negative ions get attached to aerosols. The charge level obtained from generation reduces under bipolar ion field but increases enormously under unipolar ion field. The charged aerosol concentration decay is not changed significantly under bipolar ion field when compared to the baseline condition but enhanced by more than one order under unipolar ion field.

Mobility analysis of nanocluster formation and growth from titanium tetraisopropoxide in a flow tube reactor

In an effort to understand the earliest stages of nanocluster growth in gas phase synthesis systems, we apply a flow tube reactor with a differential mobility analyzer-Faraday cage electrometer system to examine nanocluster formation and growth in the sub-3.0 nm mobility diameter range from the decomposition of titanium tetra-isopropoxide (TTIP) in air. Measured mobility distributions are inverted accounting for the DMA transfer function, tubing losses, and the charging efficiency, estimated from a non-steady state charge model within a bipolar ion source. Measurements reveal two types of species in spectra. First, we detect discrete (narrow) peaks falling in the 0.5 nm–1.5 nm size range which appear at different locations for positive and negative measurement modes. Second, we observe a larger, broadly distributed peak, which is similar in intensity for both positive and negative modes after data inversion, and which increases in intensity (concentration) and peak diameter with increasing precursor flow rate, increasing reactor temperature, and increasing residence time. We conclude that the latter broad peak arises from growing nanoclusters in the reactor. The narrower, sub 1.5 nm peaks, are most likely attributable to specific reactive intermediates from the decomposition of TTIP. We find that increasing TTIP concentration, reactor temperature, or increasing residence time, which furthers the extent of nanocluster formation, leads to the depletion of the sub 1.5 nm ions. Because of the large step size in diameter between neighboring sub 1.5 nm peaks, we also find it is unlikely that these peaks arise from small TiO2 clusters. Therefore, our measurements suggest that nanocluster growth from TTIP is facilitated by surface growth of reactive intermediates from TTIP decomposition, with reactive intermediates detectable via mobility analysis. Furthermore, while nanocluster formation and growth is clearly detected, measurements do not make clear that the nanoclusters are fully oxidized TiO2 nanoclusters for the synthesis temperature range examined.

Analysis of Wastewater Treatment Technology Based on Bipolar Membrane Electrodialysis

Metal wastewater and saline wastewater are two major problems in the field of wastewater treatment. At present, common treatment methods include ion exchange, electrodialysis and reverse osmosis. The ion exchange method often uses chemical reagents to achieve regeneration, which is likely to cause secondary pollution after treatment. Electrodeionization technology can continuously operate to treat wastewater, and does not require the use of acid-base reagents to achieve resin regeneration, but the structure is complex and requires higher pretreatment. Bipolar membrane electro-regenerative ion exchange is a new technology that has been practically applied in water supply treatment by a certain enterprise. A considerable degree of ion exchange capacity, after reaching the exchange capacity, the bipolar membrane is used for water dissociation to achieve electrical regeneration of the membrane. On the basis of investigating the desalination and regeneration of groundwater (well water) by this technology, this paper studies its removal effect on simulated food processing salty wastewater, Cu2+ and Fe2+ containing simulated electroplating rinsing wastewater. Influence of operating conditions such as influent flow on the treatment effect.

Dielectric Barrier Discharge as Bipolar Ion Source for Aerosol Charging: Application to Filtration, Thin Film and Aerosol Size Measurement

Dielectric Barrier Discharge as Bipolar Ion Source for Aerosol Charging: Application to Filtration, Thin Film and Aerosol Size Measurement

Factors Affecting Hydroxide Ion Concentrations in Bipolar Membranes

The useful lifetime of bipolar ion exchange membranes is often limited by nucleophilic attack by hydroxide ions on the ionic groups and polymer backbone in the anion exchange layers (AELs). This is especially problematic in water treatment applications for making acid and base from salt solutions. This research investigated the effect of bulk electrolyte composition, current density, membrane thickness, ion exchange capacity, and bulk solution pH value on hydroxide ion concentrations inside the AELs of a bipolar membrane. Onedimensional Nernst-Plank equations were solved for the species Na+, Cl-, OH- and H+ within 20-100 μm thick anion and cation exchange layers with fixed charged densities ranging from 0.5-2.0 eq/L. In 1 M NaCl solutions at neutral pH values, hydroxide concentrations in the AEL reached as high as 2.2 M at a current density of 100 mA/cm2. In 1 M NaOH solutions, hydroxide ion concentrations reached as high as 3.77 M. Hydroxide concentrations in the AEL were significantly affected by the ratio of Cl- to hydroxide ions in the bulk electrolyte. Where hydroxide concentrations in the bulk electrolyte were an order of magnitude lower than chloride concentrations, membrane hydroxide concentrations were nearly proportional to the current density. Increases in ion exchange capacity and AEL thickness resulted in increased membrane hydroxide ion concentrations. Membrane concentrations of hydroxide ions can be minimized by operation at low current densities, with high background electrolyte concentrations using thin membranes with low ion exchange capacities and producing base concentrations less than 0.1 M.

The nano-scanning electrical mobility spectrometer (nSEMS) and its application to size distribution measurements of 1.5–25 nm particles

Abstract. Particle size measurement in the low nanometer regime is of great importance to the study of cloud condensation nuclei formation and to better understand aerosol–cloud interactions. Here we present the design, modeling, and experimental characterization of the nano-scanning electrical mobility spectrometer (nSEMS), a recently developed instrument that probes particle physical properties in the 1.5–25 nm range. The nSEMS consists of a novel differential mobility analyzer and a two-stage condensation particle counter (CPC). The mobility analyzer, a radial opposed-migration ion and aerosol classifier (ROMIAC), can classify nanometer-sized particles with minimal degradation of its resolution and diffusional losses. The ROMIAC operates on a dual high-voltage supply with fast polarity-switching capability to minimize sensitivity to variations in the chemical nature of the ions used to charge the aerosol. Particles transmitted through the mobility analyzer are measured using a two-stage CPC. They are first activated in a fast-mixing diethylene glycol (DEG) stage before being counted by a second detection stage, an ADI MAGIC™ water-based CPC. The transfer function of the integrated instrument is derived from both finite-element modeling and experimental characterization. The nSEMS performance has been evaluated during measurement of transient nucleation and growth events in the CLOUD atmospheric chamber at CERN. We show that the nSEMS can provide high-time- and size-resolution measurement of nanoparticles and can capture the critical aerosol dynamics of newly formed atmospheric particles. Using a soft x-ray bipolar ion source in a compact housing designed to optimize both nanoparticle charging and transmission efficiency as a charge conditioner, the nSEMS has enabled measurement of the contributions of both neutral and ion-mediated nucleation to new particle formation.

Dual needle corona discharge to generate stable bipolar ion for neutralizing electrosprayed nanoparticles

The performances of dual needle corona discharge (NCD) as bipolar ion source to neutralize the electrospray (ES) particles were characterized and optimized. The NCD was constructed from a tungsten needle and grounded mesh electrode in the needle-to-plane configuration. The dual NCD created a bipolar ion environment by mixing the balanced concentration of positive and negative ions produced by each NCD. The dual NCD was placed in an electrospray aerosol generator (EAG) apparatus to reduce the charge state of the ES particles. Polystyrene latex (PSL) suspensions having the particle size range of 96–256 nm were used as the precursor solution for the electrospray process. Some characterizations to the NCD were carried out to obtain optimum operating voltage and air flow rate. The size distribution and charge fraction of the electrospray PSL (ES-PSL) particles exiting the EAG were also investigated. The result showed the dual NCD could generate stable bipolar ions by mixing positive and negative ions with balanced concentration. The bipolar ions from the dual NCD were capable of neutralizing and reducing the charge state of highly charged ES-PSL particles larger than 100 nm. The EAG, equipped with the dual NCD, could generate ES-PSL particles with stable concentration and consistent size distribution. The charge fraction calculation of the ES-PSL particles showed that more than 80% of the particles exiting the EAG were positively charged.

Efficient approach for exploring the multiple-channel bimolecular interactions of conformationally flexible reagents. Epoxide ring opening reaction

Algorithm for generation and assessment of probability of possible reaction pathways for multiple-channel bimolecular interactions is presented. The proposed algorithm comprises a combination of few steps. They include conformational search for reaction intermediate using the molecular mechanics (MMX) approach, based on the obtained conformation construction of structures of transition states and pre-reaction complexes, and calculation activation energies to further determine the probable reaction pathways. The proposed algorithm could be adopted for investigation of chemical and biochemical reactions of different types. Here, we have considered the reaction of bicyclo[2.2.1]hept-5-en-endo-2-ylmethylamine (1) with glycidyl ether (2) in a neutral environment that proceeds through SN2-like mechanism forming bipolar ion (3) which is a good starting point for identification of the reaction channels. Conformational properties of intermediate (3) have been investigated using stochastic conformational search. From the 95 localized conformations within 10 kcal/mol of global minimum that have been obtained, 63 unique transition state conformations were generated and optimized by using the PM7 and M062X/6-31G(d) methods for accurate estimation of overall rate constant of reaction. The most energetically favorable pathways have been investigated at the M062X/6-31G(d) level of theory taking into account the influence of solvent.

Recovery of ammonia nitrogen from landfill leachate using a biopolar membrane equipped electrodialysis system.

In this paper, a laboratory-scale electrodialysis reactor with five compartment cells separated by a bipolar membrane and ion exchange membrane was assembled to remove ammonia nitrogen from landfill leachate as a pretreatment process. The effects of humic acid, magnesium ions (Mg2+) and calcium ions (Ca2+) existing in leachate on the removal efficiency of ammonium (NH4 +) were investigated by using simulated wastewater. The results indicate that humic acid has little impact on ammonium in the presence of an electric field. High concentrations of Mg2+ and Ca2+ in solution have a substantial impact on the removal efficiency of ammonium, but the average migration rate of the three ions is NH4 + > Mg2+ > Ca2+ under the same current intensity, and NH4 + plays a major role in electromigration for mixture electrodialysis. Therefore, ammonia nitrogen can be separated from leachate and accumulated effectively. Meanwhile, the bipolar membrane near the cathode produces alkali that is released into the base cell to promote ammonia nitrogen transformation from accumulated ammonium, which creates in-site alkaline condition for ammonia nitrogen recovery by a further stripping process. When the actual leachate collected from a local municipal sanitary landfill was employed, the reactor reached 86.17% of ammonia nitrogen removal after 3.0 h reaction. Analysis of membrane scale suggests the inhibitory effect of Mg2+ on Ca2+ migration during the initial working period of the reaction can potentially slow down the membrane scaling of the cation exchange membrane. This study provides a promising technology for the removal and recovery of ammonia nitrogen from landfill leachate.