Low Ion Content Research Articles

Efficient synthesis of high vinyl polybutadiene based on continuous flow microchannel reactor

AbstractThe traditional batch synthesis of liquid rubber faces issues such as low monomer polymerization concentration, poor uniformity of the reaction system, and inadequate heat dissipation, resulting in an unsatisfactory synthesis efficiency. This study presents a method for the rapid and efficient synthesis of high vinyl 1,2‐polybutadiene liquid rubber using butadiene as the monomer and n‐butyllithium as the initiator. By applying continuous flow microchannel reactors, the limitation of traditional synthesis method can be overcome. The addition of a modifier in the raw material promotes the formation of high vinyl structure. The preparation of liquid rubber requires the addition of a large amount of metal lithium initiator. However, for aerospace sealants, there is a requirement for low metal ion content. To address this, we employed different methods to reduce the metal ion content in the liquid rubber and increase its purity. Ultimately, we achieved the synthesis of high‐purity polybutadiene liquid rubber with 1,2‐vinyl content exceeding 88%, narrow molecular weight distribution, and tunable molecular weights. This research will provide technical guidance for the industrial application of polybutadiene synthesis in continuous flow microchannel reactors.

Environmental significance of the interaction between titanium dioxides and soil solutions

Nanotechnology, especially in the field of photocatalysis, has witnessed rapid advancements, with titanium dioxide being one of the most widely used photocatalysts. As the use of products containing photoactive nanomaterials increases, concerns have arisen regarding their potential release into the environment over time. This release can impact soil, groundwater, and surrounding ecosystems, resulting in nanoparticles being dispersed in water and eventually depleted from the system. This study aimed to investigate how different soil solutions affect the structural, textural properties, and photocatalytic activity of titanium dioxide-based, commercial reference Evonik Aeroxide P25. The Regosol soil solution, characterized by acidic pH, low ionic content, and high organic matter content, induced nanoparticle aggregation and bandgap changes. In addition, the acidic pH hindered the adsorption process, potentially affecting the photocatalytic processes. In contrast, the Chernozem soil solution, with slightly alkaline pH, high ionic content, and low organic matter content, did not significantly alter the morphology or structure of the material. However, various organic compounds were absorbed on the surface, reducing the availability of active sites. The study highlights the importance of understanding the influence of soil solutions on nanomaterials, as it impacts their properties and environmental risks. Results show that the material is still activated, i.e., it can exert its photoactive effect on the environment. This sheds light on the challenges posed by nanoparticles in soil, particularly in terms of their toxicity and consequences for the surrounding ecosystems. The study underlines the need for further research in this area to assess potential risks and optimise the use of nanomaterials in environmental remediation.

Use of cold waters geochemistry as a geothermal prospecting tool for hidden hydrothermal systems in Réunion Island

Most untapped high-enthalpy geothermal resources are blind, meaning lacking surface evidence of their existence. The first step in their discovery is to find evidence of hydrothermal activity. Here we apply an approach based on the geochemistry of cold waters, which allowed us to identify evidence of the existence of a hydrothermal system at Piton de la Fournaise volcano (Réunion Island), and constrain its location. This approach uses the concentrations in B, Li, SO4, F, Mo, P, V, As and HCO3 and the isotopic ratios δ13C and δ11B as geochemical markers of hydrothermal activity that can be used even in waters with extremely low ion content (Electrical conductivity <80 µS/cm), and even when their geochemical composition is mainly controlled by other processes. This noninvasive approach is easy to implement and can be applied wherever the presence of a blind geothermal system is suspected.

Relationship between Water Quality in Coal Mine Voids and Dental Health

Dental and oral health is a major challenge in East Kalimantan, and nearly 73% of the population has problems with oral health. Water quality is an important factor that causes tooth decay through enamel demineralization. In the context of coal mining, high water acidity is primarily due to the presence of pyrite sulfide minerals and low fluoride ion content. Therefore, this study aimed to analyze the relationship between water quality, oral hygiene (OHIS), and the level of dental health in people who consume post-mining void water. The method was analytic observation with a cross-sectional approach, and the instruments used were the oral hygiene index, dental caries index, acidity level of water, and fluorine content test. The population included people who lived in void water areas after coal mining, and the sample included post-coal mining void water users. The sample was selected using a purposive sampling method with inclusion and exclusion criteria. The dependent variable was dental caries, whereas the independent variables were post-mining void acid water, fluorine content, and oral hygiene. The procedure of this study included testing water samples at the location with a pH meter, testing the fluorine content in the laboratory using spectrophotometry, examining oral hygiene with the oral hygiene index, and assessing tooth decay with the DMFT index. The results showed that there was a relationship between the level of acidity (pH), fluorine content, oral hygiene, and the level of dental health (DMFT) in people who use coal mine void water.

Crosslinked Polynorbornene-Based Anion Exchange Membranes with Perfluorinated Branch Chains

To investigate the effect of perfluorinated substituent on the properties of anion exchange membranes (AEMs), cross-linked polynorbornene-based AEMs with perfluorinated branch chains were prepared via ring opening metathesis polymerization, subsequent crosslinking reaction, and quaternization. The crosslinking structure enables the resultant AEMs (CFnB) to exhibit a low swelling ratio, high toughness, and high water uptake, simultaneously. In addition, benefiting from the ion gathering and side chain microphase separation caused by their flexible backbone and perfluorinated branch chain, these AEMs had high hydroxide conductivity up to 106.9 mS cm-1 at 80 °C even at low ion content (IEC < 1.6 meq g-1). This work provides a new approach to achieve improved ion conductivity at low ion content by introducing the perfluorinated branch chains and puts forward a referable way to prepare AEMs with high performance.

Ohmic charging in capacitive deionization: Efficient water desalination using capacitive spacers

AbstractCapacitive deionization (CDI) is a promising desalination technology based on electrosorption on the surfaces of microporous electrodes. However, low total dissolved solids (TDS) in the water restricts its efficacy. In this work, we develop the theory of capacitive spacers (CS) in CDI. The investigations reveal a mechanism that we call ohmic charging; that is, the resistive losses in the spacer region drive adsorption in the CS. As a consequence, the obtained results show that such spacers can improve desalination efficiency, especially at ion‐starved conditions. The spacers also enhance the charging rate of the electrodes because the overall resistance is lower when the current can pass the spacer material instead of the solution, through the adsorption of anions on one side and cations on the other. Going deeper, the investigations reveal a major challenge; the spacer naturally discharges on the same timescale as the electrode charging timescale. However, only the fast timescale matters with low ionic content solutions, and under these conditions the CS are found to be superior. Put together, CS can make a significant difference, especially when the ion concentration is low or the cycle times are short.

Geochemical transformations of sulfur in salt lakes (Transbaikalia)

The water column in brackish and saline lakes hosts various forms of sulfur including sulfide (hydrosulfide), elemental, thiosulfate, and sulfate sulfur. The unequal distribution of these reduced sulfur species indicates the presence of two opposing processes - sulfate reduction and oxidation of newly formed hydrogen sulfide. The scale of these processes varies among lakes, resulting in differing proportions of reduced sulfur forms. The bacterial reduction of sulfate ions is confirmed by a significant separation of sulfur isotopes into sulfide and sulfate ions, with the lighter isotope accumulating in the former and heavier isotope in the latter. In most soda, chloride, brackish, and salt lakes, sulfate reduction is the principal process responsible for relatively low sulfate ion content. Additionally, the presence of an oxidizing environment and sulfides in host rocks provide additional sources for sulfates, leading to the formation of sulfate-type lakes. The formation of specific types and subtypes of brackish and salt lakes is determined by processes such as water evaporation, dissolution of aluminosilicates, sulfate reduction, and oxidation of sulfides. The dominance of these processes contributes to the geochemical diversity of lakes.

Adsorption of the emerging pollutants on Buena Vista landfill cover material and implications on regional aquatic pollution

The occurrence of emerging pollutants in water represents a health risk for humans and the ecosystem. It has been shown that pollutant–soil interactions are determinants in preventing contamination of water sources by leachates from landfills. In this work, batch experiments were conducted to study the soil sorption process of amoxicillin (AMX), acetaminophen (ACP), levonorgestrel (LNG), and chlorothalonil (CTL) in four different soil layers used as cover material in Buena Vista landfill located in the municipality of La Union (Antioquia, Colombia). All soil layers were characterized using FT-IR, XRF and BET experimental techniques. In addition, pH and ionic strength effects on the adsorption process were also evaluated. The % of removal follows the order CTL > LNG > AMX > ACP in all soil layers. ACP y AMX adsorption was best described by pseudo-second-order kinetics, while LNG and CTL adsorption was best fitted by the pseudo-first-order kinetic model. Pollutant adsorptions were found to be favored at pH 6.3. Increasing the solution ionic strength decreases the adsorption of pollutants in all evaluated soil layers. The adsorption process was governed by hydrophilic and hydrophobic interactions. Polar molecules such as AMX and ACP remain in the aqueous phase while nonpolar LNG and CTL interact with clay minerals in the soil surface, presumably through van der Waals forces. Based on our findings, a cover material with both hydrophilic and lipophilic characteristics operating close to neutral, and with low ionic content, is advised for the Buena Vista landfill to improve its role as a barrier in decreasing potential pollutants contaminating groundwater sources.

An integrated assessment approach for fossil groundwater quality and crop water requirements in the El-Kharga Oasis, Western Desert, Egypt

Study regionThe El-Kharga Oasis in the Western Desert of Egypt is selected as the study area due to its hyberarid climate condition and water scarcity. In this region, the fossil groundwater is the main water source; therefore, preserving groundwater quality and quantity is mandatory. Study focusThis study evaluated groundwater suitability for irrigation purposes and assessed the water requirements of cultivated crops to optimize the water supply in hyperarid climate regions. In total, 79 deep groundwater samples were hydrochemically tested to determine the suitability for irrigation by assessing the key water quality parameters. Spatial distribution maps of all chemical parameters, such as pH, EC, SAR, RSC, SSP, TDS, total hardness, Na+, K+, Ca++, Mg++, Fe, Mn, Cl-, and SO4—, were developed. The FAO CROPWAT 8.0 model, based on the Penman–Monteith equation, was used to forecast agricultural water requirements for three years, 2010, 2011, and 2012. New hydrological insights for the regionThe groundwater had medium salinity and low sodium in 84% of the cases. In comparison, high salinity was found in 16% of the samples, indicating that groundwater can be used for many soil types with a low risk of exchangeable sodium. Except for 15 of the 79 wells, all groundwater samples had chloride concentrations less than 100 mg/l. The sulfate ion distribution map showed a low sulfate ion content in the extreme western south. The total annual irrigation water requirements of all crops for 2010, 2011 and 2012 were 199.4, 215.1, and 231.7 million m3/year, respectively, reflecting a gradual increase of approximately 16.57 million m3/total area/year due to the expansion of the cultivated area. The analysis showed that modern irrigation systems reduced the amount of irrigation water by 32% and increased the cultivated area by 45% compared to conventional irrigation methods. Severe groundwater depletion occurred during the dry season from March to July, which exacerbated the water stress in the study region. The results confirmed that the region is under water stress. Accordingly, water conservation is urgently recommended.

500-A LaB6 Hollow cathode for high power electric thrusters

NASA continues to develop higher power ion and Hall thrusters for deep space human and robotic missions that require higher thrust and specific impulse than available in current thrusters. The NASA XR-100 nested Hall thruster successfully operated at 100 kW of power; driven by a JPL LaB6 hollow cathode that produced up to 250 A of discharge current in the thruster and 25–350A in the cathode test facility. The next generation of this LaB6 hollow cathode has been designed and built at JPL and tested at up to 500 A of discharge current. Extending the current to this high level was challenging, with iterations in the design necessary to provide adequate thermal isolation of the insert to lower the heater power required to ignite, to achieve sufficient keeper discharge current to aid in the startup, and to maintain the cathode orifice plate at acceptable temperatures during very high current operation. The 2nd generation version of the cathode successfully achieved 500 A of discharge current operation with low high-energy ion content. Discussions of the plasma instabilities observed in the plume, the plasma penetration into the insert region, and cathode life are provided.

The role of Zn2+-doping on the surface chemistry of poly(vinylidene difluoride) thin films

Thin films of poly(vinylidene difluoride) (PVDF) doped with zinc nitrate spin-cast onto silicon substrates were studied by optical profilometry, infrared and x-ray photoelectron spectroscopy (XPS). The spin-cast films were found to be significantly nonuniform having variations on the order of hundreds of nanometers across tens of microns for films with low zinc ion content and with pores that extend through the entire film thickness. As the Zn2+ content increases both the porosity and the amount of β-phase of the PVDF in the bulk of the films increase. The depth of some of the pores allowed investigation of both the polymer/air and polymer/substrate interface. The increased porosity of the doped films is tentatively attributed to Marangoni effects.

How soil ion stress and type influence the flooding adaptive strategies of Phragmites australis and Bolboschoenus planiculmis in temperate saline–alkaline wetlands?

Soil saline–alkaline stress and flooding extremes have been projected to be the main factors influencing the degradation of marsh plants in wetlands worldwide, which would affect their ecological functions (i.e. food source for migrating birds). Plants cope with flooding either by escaping from below water through shoot elongation or by remaining quiescent until water subsides. However, little is known about the adaptive strategies of Phragmites australis and Bolboschoenus planiculmis to flooding combined with salinity–alkalinity, which are the key environmental filters in Western Songnen Plain, China. Accordingly, this study investigated the adaptive strategies of P. australis and B. planiculmis subjected to the interacting effects of flooding and soil ion stress under field and greenhouse conditions. Results showed that the two species adopted different strategies to survive flooding. P. australis exhibited an escape strategy because of leaf and shoot elongation with increasing flooding depth whereas B. planiculmis became quiescent with no or deceased leaf and shoot elongation and biomass accumulation. High soil ion stress changed the flooding adaptive strategy of P. australis to a quiescence strategy, whereas B. planiculmis remained quiescent with increasing flooding depth at each soil ion content. The strategies of the two species were changed by alkaline ion stress but not by saline ion stress, and they exhibited different adaptive responses. High alkaline ion stress induced P. australis to remain quiescent with increasing flooding depth, whereas low alkaline ion stress promoted B. planicumis to escape from below water, probably due to the buffer effect of low alkaline ion contents outside the roots probably. Hence, P. australis and B. planicumis might adopt the quiescence strategy with increasing degree of soil salinization and alkalization under high greenhouse gas emissions scenarios in Western Songnen Plain, which may lead to severe degradation of the two kinds of marshes in the future.

The strength and durability of steel fibre recycled concrete in chloride environments

The strength and durability of structures are strongly influenced by damage from steel corrosion caused by chloride ions. This chloride-induced corrosion mechanism is investigated yearly. However, the strength and durability of steel fibre recycled concrete (SFRC) in chloride environments have rarely been studied. By changing the water–cement ratio of SFRC blocks, the sodium chloride (NaCl) concentration of the soaking solution, soaking time and the number of chloride-ion-permeating surfaces, a series of compressive strength experiments were performed, where the chloride ion content of tested blocks was measured. The results showed that the water–cement ratio of blocks greatly influences the strength and durability of SFRC and that the sodium chloride concentration of the soak solution, and the number of chloride-ion-permeating surfaces, also affects the blocks to a certain degree. A water–cement ratio of 0·45 should be chosen due to its low chloride ion content and high compressive strength. The water–cement ratio and the number of chloride-ion-permeating surfaces can be controlled more easily in practical engineering, it is therefore necessary to optimise the best water–cement design ratio and add a water-repellent coating on the SFRC surfaces to ensure the durability of the structure.

Coulomb interaction-driven UCST in poly(ionic liquid) random copolymers

Upper critical solution temperature (UCST)-type thermoresponsive phenomena is not very common in conventional hydrophobic or hydrophilic polymers in aqueous solution. The incorporation of poly(triphenyl-4-vinylbenzylphosphonium chloride) (P[VBTP][Cl]), poly(ionic liquid) (PIL) segment with either hydrophobic poly(methyl methacrylate)(PMMA)/polystyrene (PS) or hydrophilic poly(hydroxyethyl methacrylate)(PHEMA)/poly(N-isopropyl acrylamide)(PNIPAM) segments via reversible addition–fragmentation chain transfer (RAFT) copolymerization is a simple, yet versatile approach for introducing UCST property in their random copolymers. These PIL copolymers exhibit UCST-type behaviours in aqueous or in methanol solution depending on their compositions in the presence of externally added halide anion (Cl− and I−). The cause of UCST is the formation of copolymer aggregates by anion-bridging Coulomb interactions followed by their disruption upon heating. The cloud points of these copolymers can easily be tuned with respect to the copolymer compositions as well as concentrations of anions. Whereas, the random copolymer of P[VBTP][Cl] and PNIPAM segments with low (ca. 1.1–19.3 wt%) ionic PIL content show lower critical solution temperature (LCST)-type behaviour and its cloud point increases linearly with increasing ionic PIL content. More interestingly, P[VBTP][Cl]-ran-PNIPAM copolymer containing high (ca. 34.5 wt%) percentage of ionic PIL segment simultaneously show a LCST-type transition at lower temperature followed by an UCST-type transition at higher temperature in the presence of chloride ions. Tuning of both the LCST-/UCST-type cloud points is possible by varying the concentrations of copolymer and the added chloride ion.

Micro-analysis of Marine Sand From Zhoushan Seas

The main salt components and ion content of seawater were qualitatively and quantitatively analyzed. The results show that the seawater in this region has low ion content and low salt content, and direct application is relatively beneficial to engineering. Meantime, the property test was carried out to investigate the basic physical behavior of the goal sea sand. The results show that Zhoushan sea sand has low chloride ion content, uniform particle size and Low mud content.

Analysis of metal ion impurity in tetraethyl orthosilicate by sector field inductively coupled plasma mass spectrometry

A sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) method was developed to directly analyze metal ion impurity in tetraethyl orthosilicate (TEOS). As trace metal ion impurity in TEOS can cause a damaging effect on wafer-product-based electronic devices, it is necessary to develop an efficient analytical method for quantifying the trace metal ions in TEOS for semiconductor manufacturing. The low metal ion content (nanogram per liter level) in a TEOS solution is difficult to be analyzed directly by SF-ICP-MS. Pretreatment such as acidic digestion and direct dilution results in lower concentrations of the metal ions down to picogram per liter level which reaches the instrumental limitation and is not suitable for analysis. In this study, simple liquid–liquid extraction (LLE) was applied by adding isopropanol and deionized water to extract the metal ion in TEOS. The interfering compounds can be directly separated from the analyte by SF-ICP-MS with an appropriate resolution, thereby preventing any ambiguity in the identification of metal ions. The maximum concentration factor was 18.94. The applicability of the proposed method has also been validated by the analysis of three TEOS samples for different applications. The concentrations of metal ions with the range from nanogram per liter to microgram per liter can all be determined with good precision (RSD < 9.46%) and good accuracy (spike recoveries from 94% to 113%). This study demonstrates that SF-ICP-MS with LLE pretreatment is a promising approach for analyzing metal ion impurity in TEOS.

Preparation of proton permselective composite membrane and its application in waste acid reclamation by ion substitution electrodialysis

Nowadays, the reclamation of industrial waste acid characterized with low acid concentration and high metal ion content has attracted much attention. How to carry out effectively a separation between protons and metal ions becomes a top priority. In this report, a so-called proton permselective composite membrane was prepared specifically for waste acid reclamation by electrodialysis. Above all, a porous supporting membrane was prepared from polysulfone via classical wet phase inversion technology. Therein appropriate amount of sulfonated polysulfone (SPSF) was added to adjust its microstructure. Subsequently, a hydrophilic composite layer, such as Poly(ethylene imine) layer or Poly(vinyl alcohol) layer, was used to endow the proton permeability based on the unique transport mechanism of protons in which water molecules play an important role. ATR-FTIR and SEM were employed to monitor the changes in chemical composition and microstructure of as-prepared membranes, respectively. Furthermore, their electrodialytic transport properties, including electrical resistance, limiting current, water transport behaviors, proton permselectivity and anion-blocking ability, were investigated and compared with those of typical commercial cation-exchange membrane. As confirmed by series of electrochemical characterizations, as-prepared composite membranes, especially PVA-Series membranes, exhibited outstanding work performances and remarkable practical value in the acid recovery. At last, the ion substitution electrodialysis for waste acid reclamation in which typical composite membranes were assembled were also conducted to examine the process energy consumption, the concentration and purity of the produced acid.

The effect of saline-alkaline and water stresses on water use efficiency and standing biomass of Phragmites australis and Bolboschoenus planiculmis

Salt marsh plants in the West Songnen Plain, northern China, are threatened by increasing soil salinity and alkalinity since the late 20th century. To explore how these wetland ecosystems respond to such environmental changes, we examined the effect of saline-alkaline stresses and water stress (flooding/drought) on water use efficiency (WUE, assessed with stable carbon isotopes) and standing biomass of Phragmites australis and Bolboschoenus planiculmis under both greenhouse and field conditions. In the field, sodium bicarbonate (NaHCO3) was the main saline-alkaline component, and the soil total ion content was negatively related to water level. Higher soil ion content decreased standing biomass of P. australis and B. planiculmis in the field and greenhouse, and increased WUE in the greenhouse. With higher water level, standing biomass of P. australis increased, while that of B. planiculmis decreased in both the field and greenhouse. Alkaline stress exerted the greatest negative influence on growth of P. australis, but only under high ion content. Low alkaline ion content promoted growth of B. planiculmis. Soil ion content exerted the strongest influence on foliar δ13C (and thus WUE) and standing biomass of both species compared to water level and stress type. Our findings suggest that under high ion contents, P. australis is more tolerant to flooding stress while B. planiculmis is more tolerant to drought stress. Moreover, P. australis has a high ability to modulate and increase WUE to resist its adverse environment. Our study will contribute to a better understanding of the influence of climate change and increasingly serious human disturbances on the distribution and productivity of these two important wetland species.

Modeling the pH-ammonia toxicity relationship for Hydra viridissima in soft waters with low ionic concentrations.

There are limited data concerning the toxicity of ammonia in fresh soft waters. Ammonia toxicity is largely dependent on pH and temperature. The US Environmental Protection Agency (USEPA) has derived equations to adjust species toxicity estimates based on changes in pH and temperature. It has been reported that the pH-ammonia toxicity relationship, derived by the USEPA, may differ in waters with low ionic concentrations because of the absence of potentially ameliorative ionic constituents. The present study aimed to assess the pH-ammonia toxicity relationship for the tropical green hydra, Hydra viridissima, across a range of pH values in a natural water with low ionic content. Ammonia toxicity to H. viridissima was assessed at a pH range between 6.0 and 8.5 and temperature 27.5 ± 1 °C. Test solution pH was maintained using a pH buffer. The resulting median effect concentrations ranged from 9.62 (7.95-11.65) mg L-1 total ammonia nitrogen at pH 6.0 to 0.64 (0.50-0.81) mg L-1 total ammonia nitrogen at pH 7.9. The results indicated that increasing pH increased the sensitivity of H. viridissima to ammonia. The pH dependence equation derived by the USEPA accurately described the relationship between pH and ammonia toxicity for H. viridissima. However, when the model parameters for the generic pooled relationship were used, the fit was less accurate (r2 = 0.66), indicating that the generic pooled pH-dependence equations may not be appropriate for use with this species. Environ Toxicol Chem 2018;37:1189-1196. © 2017 SETAC.

Corrosion of Post-Tensioned Tendons with Deficient Grout, Part 2: Segregated Grout with Elevated Sulfate Content

Corrosion failure of post-tensioning (PT) tendons with pre-packaged thixotropic grout has been documented in Florida bridges. Analysis of the deficient grout in Florida PT bridges, where severe corrosion developed, indicated elevated sulfate ion concentration, high pore water pH, low chloride ion content, and enhanced moisture content. Limited information is available on the corrosion behavior of PT strand in grout materials with elevated sulfate ion content. In this work, the corrosion performance of steel strands embedded in deficient grout was evaluated. The deficient grout was cast in large scale test assemblies that would represent geometry and material conditions found in Florida bridges, where PT strand corrosion occurred. Large scale mock up tendons (developed by the modified inclined tube [MIT] test) of about 4.57 m long were cast using expired grout materials, excess of 15% water, and sulfate ion concentrations to create deficiencies and corrosion conditions in the grout environment. Corrosion measurements such as corrosion potential (Ecorr) and corrosion current density (icorr), as well as potentiodynamic polarization tests were performed on the steel probes located along the MIT samples in contact with the deficient grout. Grout characterization parameters included the determination of the grout resistance (Rs), as well as the moisture and sulfate ion content. Also, visual inspection of the MIT samples (steel strand and steel corrosion probes) after a time was performed, as well as the corrosion products characterization. Testing confirmed that enhanced corrosion can occur in the deficient grout with high free sulfate ion accumulation.