Divalent Ions Research Articles

Kappa carrageenan-vanillin composite hydrogel for landfill leachate wastewater treatment

Removing heavy metals from landfill leachate wastewater treatment is an environmental challenge because of its complicated characteristics and composition. Although several chemical and physical processes were developed for landfill wastewater treatment, membrane technologies are still common. Nevertheless, membrane fouling, energy requirements and brine management are drawbacks of membrane technologies. This study proposed a biodegradable, gravity-driven kappa-Carrageenan-vanillin hydrogel for biologically treated leachate wastewater treatment to reduce the treatment cost and brine management problem. The composite hydrogel was synthesized using a facile method, with an average pore size of 2.58 ± 0.5 nm and acts as a water filter with super high flux and excellent rejection for heavy metal ions, divalent ions and other contaminants in the landfill leachate wastewater. The hydrogel filter achieved high rejection for divalent ions from salt feed solutions such as sodium chloride, magnesium sulphate, and copper sulphate. An average rejection of 42 ± 5 % was achieved for sodium chloride, 78 % ± 5 % for copper, 72 % ± 5 % for divalent magnesium ion, and 17 % ± 5 % for sulphate rejection. The hydrogel filter achieved a flux of 27 ± 5 LMH for landfill leachate wastewater with high rejection efficiency for total organic carbon, turbidity, and heavy metal separation. The filtration of the landfill leachate with the hydrogel resulted in a high rejection of total organic carbon (77 ± 3 %), 95 ± 3 % turbidity removal, 73 ± 5 % TDS removal, and 95–97 % colour removal. Heavy metal ions were rejected in the following order: Al (80 ± 3 %) > Ba (88 ± 2 %) > Pb (79 ± 3 %) > Cd (72 ± 3 %). The composite hydrogel filter is inexpensive, reliable, and highly efficient in removing contaminants under gravity filtration, requiring no external energy or high hydraulic pressures and ease of scalability for commercial applications.

Monovalent and Divalent Ions Impair Recovery of Strength when Self-Healing Is Facilitated by Hydrogen Bonding

Monovalent and Divalent Ions Impair Recovery of Strength when Self-Healing Is Facilitated by Hydrogen Bonding

Experimental study on the effect of tight gas fracturing flowback fluid composition on the performance of modified polyacrylamide viscosity reducing and slippery water system

AbstractTight gas belongs to unconventional gas reservoirs, and to obtain high gas production, it needs to be fractured and reformed. After the construction is completed, a large amount of flowback fluid is produced. In order to reduce the cost of flowback fluid treatment and avoid environmental pollution, a slippery water system with flowback fluid is usually used on the site of hydraulic fracturing. Almost all flowback fluids contain high‐order cations such as calcium ions, magnesium ions, iron ions, and a large amount of suspended solids. Some flowback fluids contain incomplete gel‐breaking micelles and unseparated condensate oil. The performance of the viscosity‐reducing and slippery water system with flowback fluid as the base fluid is poor, usually manifested as low viscosity of the slippery water, low friction reduction rate, and high formation damage. To study the effect of tight gas fracturing flowback fluid on the performance of modified polyacrylamide viscosity‐reducing and slippery water system, this paper found through cryo‐electron microscopy scanning experiments that the flowback fluid made the modified polyacrylamide molecular chain unable to form a complex network structure and showed the phenomenon of reduced strength and aggregation. The effects of mineralization degree, calcium and magnesium ions, divalent and trivalent iron ions, suspended solids, pH value, and oil content on the viscosity, friction reduction performance, and rock damage of the viscosity‐reducing and slippery water system were analyzed experimentally. It was found that the viscosity of the viscosity‐reducing and slippery water system was mainly affected by divalent iron ions, calcium and magnesium ions and other divalent cations; the friction reduction rate was mainly affected by the content of suspended solids and oil content; and the rock damage was mainly affected by the pH value and the content of suspended solids. Based on this, recommended parameters for reusing tight gas fracturing flowback fluid are given to guide the smooth progress of hydraulic fracturing construction on‐site.

Binding and Sliding Dynamics of the Hepatitis C Virus Polymerase: Hunting the 3' Terminus.

The hepatitis C virus (HCV) nonstructural protein 5B (NS5B) polymerase catalyzes the replication of the (+) single-stranded RNA genome of HCV. In vitro studies have shown that replication can be performed in the absence of a primer. However, the dynamics and mechanism by which NS5B locates the 3'-terminus of the RNA template to initiate de novo synthesis remain elusive. Here, we performed single-molecule fluorescence studies based on protein-induced fluorescence enhancement reporting on NS5B dynamics on a short model RNA substrate. Our results suggest that NS5B exists in a fully open conformation in solution wherefrom it accesses its binding site along RNA and then closes. Our results revealed two NS5B binding modes: an unstable one resulting in rapid dissociation, and a stable one characterized by a larger residence time on the substrate. We associate these bindings to an unproductive and productive orientation, respectively. Addition of extra mono (Na+)- and divalent (Mg2+) ions increases the mobility of NS5B along its RNA substrate. However, only Mg2+ ions induce a decrease in NS5B residence time. Dwell times of residence increase with the length of the single-stranded template, suggesting that NS5B unbinds its substrate by unthreading the template rather than by spontaneous opening.

Dielectric and gyromagnetic structure modulations of Zn–Sn codoped yttrium–iron–garnet based on the density‐generalized functional theory and P–V–L bond theory

AbstractHerein, the crystal structure, dielectric properties, and gyromagnetic characteristics of Zn–Sn codoped Y3ZnxSnxFe5−2xO12 (x = 0.0–0.5) prepared using a conventional ceramic process were investigated. According to the first‐principles’ calculations and complex crystal bonding theory, Zn2+–Sn4+ codoping can increase the relative dielectric constant (εr) by enhancing the average ionicity. The x‐ray photoelectron spectroscopy (XPS) and Raman analysis results indicate that an appropriate amount of Zn2+–Sn4+ codoping can help improve the microscopic morphology, maintain the appropriate ratio of divalent iron ions, and reduce the microwave magnetic and electrical losses of YIG ferrites. The optimized microwave properties are as follows. Y3Zn0.3Sn0.3Fe4.4O12 after sintering at 1400°C; εr = 15.6; dielectric loss, that is, tanδε = 4.3 × 10−4; saturation magnetization, that is, 4πMS = 2244 G; ferromagnetic resonance linewidth, that is, ΔH = 37 Oe. These properties can help improve the performance of high‐frequency microwave components by enhancing the properties of ferrite.

Kinetic characterization of annotated glycolytic enzymes present in cellulose-fermenting Clostridium thermocellum suggests different metabolic roles

BackgroundThe efficient production of sustainable biofuels is important for the reduction of greenhouse gas emissions. Clostridium thermocellum ATCC 27405 is a candidate for ethanol production from lignocellulosic biomass using consolidated bioprocessing. Fermentation of cellulosic biomass goes through an atypical glycolytic pathway in this thermophilic bacterium, with various glycolytic enzymes capable of utilizing different phosphate donors, including GTP and inorganic pyrophosphate (PPi), in addition to or in place of the usual ATP. C. thermocellum contains three annotated phosphofructokinases (PFK) genes, the expression of which have all been detected through proteomics and transcriptomics. Pfp (Cthe_0347) was previously characterized as pyrophosphate dependent with fructose-6-phosphate (F6P) as its substrate.ResultsWe now demonstrate that this enzyme can also phosphorylate sedoheptulose-7-phosphate (an intermediate in the pentose phosphate pathway), with the Vmax and Km of F6P being approximately 15 folds higher and 43 folds lower, respectively, in comparison to sedoheptulose-7-phosphate. Purified PfkA shows preference for GTP as the phosphate donor as opposed to ATP with a 12.5-fold difference in Km values while phosphorylating F6P. Allosteric regulation is a factor at play in PfkA activity, with F6P exhibiting positive cooperativity, and an apparent requirement for ammonium ions to attain maximal activity. Phosphoenolpyruvate and PPi were the only inhibitors for PfkA determined from the study, which corroborates what is known about enzymes from this subfamily. The activation or inhibition by these ligands lends support to the argument that glycolysis is regulated by metabolites such as PPi and NH4+ in the organism. PfkB, showed no activity with F6P, but had significant activity with fructose, while utilizing either ATP or GTP, making it a fructokinase. Rounding out the upper glycolysis pathway, the identity of the fructose-1,6-bisphosphate aldolase in the genome was verified and reported to have substantial activity with fructose-1,6-bisphosphate, in the presence of the divalent ion, Zn2+.ConclusionThese findings along with previous proteomic data suggest that Pfp, plays a role in both glycolysis and the pentose phosphate pathway, while PfkA and PfkB may phosphorylate sugars in glycolysis but is responsible for sugar metabolism elsewhere under conditions outside of growth on sufficient cellobiose.

Enhancing the Electrochemical Performance of Ternary Metallic Phosphates for High‐Energy and Anti‐Self‐Discharge Supercapacitors through Binder Optimization

Supercapacitors have proven themselves as a subject of interest over the years for energy storage. As a result, it is not surprising that significant effort has been put into supercapacitor research. However, a device with all desirable properties still needs to be developed, requiring special attention. A simple synthesis of porous magnesium niobium silver phosphate (Mg3Nb1−xAgx(PO4)3) nanocomposites is presented using a novel mixed solvent solution and a hydrothermal method. The MgNbAgPO4 anode with an interconnected porous structure not only offers a large number of active sites for divalent ion trapping but also improves charge transfer kinetics. As a result, the Mg3Nb1−xAgx(PO4)3 anode has a high specific capacity of 958 C g−1 using a binder‐free electrode and better rate capability. The full‐cell design is also built with Mg3Nb1−xAgx(PO4)3 and activated carbon (AC). The hierarchical pore structure and appropriate functional groups Mg3Nb1−xAgx(PO4)3 anode deliver a maximum energy density of 57 Wh kg−1, a high power density of 1200 kW kg−1, and anti‐self‐discharge solid behavior. The analysis of the charge storage mechanism suggests that Mg3Nb1−xAgx(PO4)3//AC supercapattery involves adsorption/desorption and Faradic reactions to store charge. This study opens the path for high‐performance Mg3Nb1−xAgx(PO4)3 electrode and gives a better knowledge of charge storage.

Reflectance spectroscopy as a promising tool for ‘sensing’ metals in hyperaccumulator plants

Main conclusionThe VNIR reflectance spectra of nickel hyperaccumulator plant leaves have spectral variations due to high nickel concentrations and this property could potentially be used for discovery of these plants. Hyperaccumulator plants accumulate high concentrations of certain metals, including manganese, cobalt, or nickel. Of these metals, the divalent ions of nickel have three absorption bands in the visible to near-infrared region which may cause variations in the spectral reflectance of nickel hyperaccumulator plant leaves, but this has not been investigated previously. In this shortproof-of-concept study, the spectral reflectance of eight different nickel hyperaccumulator plant species leaves were subjected to visible and near-infrared and shortwave infrared (VNIR-SWIR) reflectance spectrum measurements in dehydrated state, and for one species, it was also assessed in hydrated state. Nickel concentrations in the plant leaves were determined with other methods and then correlated to the spectral reflectance data. Spectral variations centred at 1000 ± 150 nm were observed and had R-values varying from 0.46 to 0.96 with nickel concentrations. The extremely high nickel concentrations in nickel hyperaccumulator leaves reshape their spectral reflectance features, and the electronic transition of nickel-ions directly contributes to absorption at ~ 1000 nm. Given that spectral variations are correlated with nickel concentrations it make VNIR-SWIR reflectance spectrometry a potential promising technique for discovery of hyperaccumulator plants, not only in the laboratory or herbarium, but also in the field using drone-based platforms. This is a preliminary study which we hope will instigate further detailed research on this topic to validate the findings and to explore possible applications.

Behaviors of actinides in chromatographic separation by using TBP resin in nitric acid solution and hydrochloric acid solution

ABSTRACT We are developing a simple actinide separation method for a pre-treatment process of actinide analysis by mass spectrometry such as thermal ionization mass spectrometry or inductively coupled plasma mass spectrometry. The actinide separation was conducted by using Tributyl phosphate (TBP) impregnated resin commercially supplied by Triskem International. TBP is commonly used in the PUREX system as a solvent for the recovery and recycling of uranium and plutonium from spent nuclear fuels through liquid–liquid separation in the HNO3 system. In this study, TBP-impregnated resin is employed as a solid extractant for the mutual separation of uranium, plutonium, thorium, and trivalent actinides through solid–liquid separation by combination with nitric acid (HNO3) and hydrochloride acid (HCl), with divalent iron ion as a reductant for valence control of plutonium. We confirmed that uranium was extracted with a recovery rate of more than 96%.

Multiphoton induced photoreduction in BaFCl: Sm3+ nanocrystals under femtosecond laser field

Photoinduced valence state conversion in lanthanide-doped solid materials can find significant applications in areas like optical storage, opto-electronic devices and has been attracting great research efforts. Here, we experimentally demonstrate that trivalent samarium ions contained in the BaFCl nanocrystals can be efficiently reduced to divalent ones under 800 nm fs laser field. The dependences of the luminescence intensity of the photoinduced divalent ions on the femtosecond laser power, central wavelength and polarization are investigated in detail, respectively. Theoretical fits of the experimental observations indicate that a resonance-mediated (2 + 2) four-photon absorption is most probably involved in the multiphoton induced photoreduction process.

Micromechanical mechanism of oil/brine/rock interfacial interactions based on first-principles calculations

Understanding the mechanisms of oil/brine/rock interfacial interactions from a nanoscale perspective is essential for enhanced oil recovery (EOR) techniques employed in the exploration of shale oil. Under formation conditions, both metal cations and water molecules could form bridging connections between rock surfaces and the polar oil components, which are referred to as hydrated ion bridges (HIB) and water bridges (WB). In this work, we have comprehensively analyzed the interaction and destruction of various HIB and WB systems. Quasi-static pulling processes were investigated based on first-principles calculations. We found that ions can increase the oil-rock interaction strength, especially for the divalent ions. Various different contributions to interfacial energy were scrutinized from several different approaches. Our results show that water-valeric acid could be the most probable destruction sites at oil/brine/rock interface. Hydrogen bonds and van der Waals interactions were visualized in an intuitive way, which enhance our comprehension on the interaction and destruction of HIB and WB connections. These findings may provide an in-depth insight into oil/brine/rock interfacial interactions and theoretical support for the effective oil extraction.

First-principles investigation of divalent ion sensing with cesium lead trihalides

The first-principles calculations of the cesium lead trihalides, CsPbX3 (X = Cl, Br and I), doped with divalent ions such as Cd2+, Cu2+, Mg2+, Ni2+, Sn2+ and Zn2+ are carried out within the density functional theory to explore ion-sensing ability of CsPbX3 for divalent ions. Here the formation energy of the divalent ions doped CsPbX3 are calculated to evaluate the ability of absorption of the divalent ions. To investigate change in photoluminescence intensity of CsPbX3 due to the divalent ions incorporation, change in electronic structures of CsPbX3 due to the divalent ions dopings are also discussed by comparing the calculated electronic density of states.

Double- or Triple-Tiered Protection: Prospects for the Sustainable Application of Copper-Based Antimicrobial Compounds for Another Fourteen Decades

Copper (Cu)-based antimicrobial compounds (CBACs) have been widely used to control phytopathogens for nearly fourteen decades. Since the first commercialized Bordeaux mixture was introduced, CBACs have been gradually developed from highly to slightly soluble reagents and from inorganic to synthetic organic, with nanomaterials being a recent development. Traditionally, slightly soluble CBACs form a physical film on the surface of plant tissues, separating the micro-organisms from the host, then release divalent or monovalent copper ions (Cu2+ or Cu+) to construct a secondary layer of protection which inhibits the growth of pathogens. Recent progress has demonstrated that the release of a low concentration of Cu2+ may elicit immune responses in plants. This supports a triple-tiered protection role of CBACs: break contact, inhibit microorganisms, and stimulate host immunity. This spatial defense system, which is integrated both inside and outside the plant cell, provides long-lasting and broad-spectrum protection, even against emergent copper-resistant strains. Here, we review recent findings and highlight the perspectives underlying mitigation strategies for the sustainable utilization of CBACs.

Identification and Expression of the CorA/MRS2/ALR Type Magnesium Transporters in Tomato.

Magnesium (Mg2+) is the most abundant divalent ion in plants, participating in numerous metabolic processes in growth and development. CorA/MRS2/ALR type Mg2+ transporters are essential for maintaining Mg2+ homeostasis in plants. However, the candidate protein and its potential functions in the tomato plant have not been fully understood. In this study, we identified seven MGT genes (SlMRS2) in tomato based on sequence similarity, domain analysis, conserved motif identification, and structure prediction. Two SlMRS2 genes were analyzed in the bacterial strain MM281, and a functional complementary assay demonstrated their high-affinity transport of Mg2+. Quantitative real-time PCR analysis revealed that the expressions of these Mg2+ transporters were down-regulated in leaves under Mg2+ limitation, with a greater impact on lower and middle leaves compared to young leaves. Conversely, under Mg2+ toxicity, several genes were up-regulated in leaves with a circadian rhythm. Our findings indicate that members of the SlMRS2 family function as Mg2+ transporters and lay the groundwork for further analysis of their distinct functions in tomato.

THE STRUCTURE OF THERMOLUMINESCENCE TRAPS IN AQUEOUS GROWN KCl

The results of TL studies in aqueous grown undoped KCl crystals are reported. A de-convolution of TL curve into five component peaks has been performed and trap depths have been obtained. The importance of bi-vacancy has been established as a fundamental trap and its anion vacancy end has also been proposed as a suitable trap for thermoluminescence in KCl crystals. The traps at anion vacancies linked to impurity vacancy I-V pairs have also been envisaged and the shift in the depths of traps is attributed to the electric field of I-V pairs in the lattice caused by inherent divalent ions. Some traps linked to hydroxyl groups have also been identified.

PTSA-mediated interfacial catalytic polymerization of crystalline dense covalent organic framework membranes for enhanced desalination

Construction of covalent organic frameworks (COF) membranes for desalination applications was challenging, mainly due to the poor crystallinity and large intrinsic pore size of COFs. Herein, the p-toluenesulfonic acid (PTSA)-mediated interfacial catalytic polymerization (ICP) strategy was proposed to fabricate COF membranes with high crystallinity and sub-nano pores on the polysulfone substrate to enhance desalination and selectivity performance. The proposed PTSA-mediated ICP strategy facilitated the amorphous-to-crystalline transformation and regulated the stacking behavior of COF crystals. Via PTSA meditated ICP process, a ribbon-like crystal structure was observed on the membrane surface. The amorphous COF layers with a thickness of 122–412 nm transformed into crystalline COF layers with a thickness of approximately 245–390 nm, while the pore radius of the COF membranes decreased from 0.65-1.25 nm to 0.17–0.25 nm due to the multilayer stacking of COF crystals on the membrane surface. Meanwhile, the crystalline degree of these COF membranes increased from 21.45% to 73.95% with increasing PTSA concentration and ICP time. The optimal TpPa3%-15 membrane had a water permeability of approximately 3.74 L−1 m−2 h−1 bar−1 and substantial enhancement of Na2SO4 rejection from 19.7% to 90.4%. The 30-day duration of the cross-flow operation measurement demonstrated excellent stability and robust selectivity of SO42− and Cl− for the optimal TpPa3%-15 membrane. In addition, the optimal membrane exhibited excellent desalination performance for divalent ions in petrochemical wastewater and shale gas produced water than that of pristine membrane, rendering their applicability for industrial wastewater desalination. The mechanisms analysis verified that PTSA induced disorder multilayer stacking of crystalline COF crystals on the substrate surface, resulting in reduced pore sizes and increased desalination of the COF membranes. As the traditional IP process, this work proposed that PTSA mediated ICP process was a facile, scalable and time-saving approach for the construction of highly crystalline COF membranes with sub-nanometer pores to achieve enhanced desalination performance.

Recent Advances of Transition Metal Dichalcogenides-Based Materials for Energy Storage Devices, in View of Monovalent to Divalent Ions.

The fast growth of electrochemical energy storage (EES) systems necessitates using innovative, high-performance electrode materials. Among the various EES devices, rechargeable batteries (RBs) with potential features like high energy density and extensive lifetime are well suited to meet rapidly increasing energy demands. Layered transition metal dichalcogenides (TMDs), typical two dimensional (2D) nanomaterial, are considered auspicious materials for RBs because of their layered structures and large specific surface areas (SSA) that benefit quick ion transportation. This review summarizes and highlights recent advances in TMDs with improved performance for various RBs. Through novel engineering and functionalization used for high-performance RBs, we briefly discuss the properties, characterizations, and electrochemistry phenomena of TMDs. We summarised that engineering with multiple techniques, like nanocomposites used for TMDs receives special attention. In conclusion, the recent issues and promising upcoming research openings for developing TMDs-based electrodes for RBs are discussed.

Insufficient desorption of ions in constant-current membrane capacitive deionization (MCDI): Problems and solutions

Membrane capacitive deionization (MCDI) is a water desalination technology that involves the removal of charged ions from water under an electric field. While constant-current MCDI coupled with stopped-flow during ion discharge is expected to exhibit high water recovery and good performance stability, previous studies have typically been undertaken using NaCl solutions only with limited investigation of MCDI performance using multi-electrolyte solutions. In the present work, the desalination performance of MCDI was evaluated using feed solutions with different levels of hardness. The increase of hardness resulted in the degradation of desalination performance with the desalination time (Δtd), total removed charge, water recovery (WR) and productivity decreasing by 20.5%, 21.8%, 3.8% and 3.2%, respectively. A more serious degradation of WR and productivity would be caused if Δtd decreases further. Analysis of the voltage profiles and effluent ion concentrations reveal that the insufficient desorption of divalent ions at constant-current discharge to 0 V was the principal reason for the degradation of performance. The Δtd and WR can be improved by discharging the cell using a lower current but the productivity decreased by 15.7% on decreasing the discharging current from 161 to 107 mA. Discharging the cell to a negative potential was shown to be a better option with the Δtd, total removed charge, WR and productivity increasing by 27.4%, 23.9%, 3.6% and 5.3%, respectively, when the cell was discharged to a minimum voltage of – 0.3 V. Use of such a method should be feasible for operation of full scale MCDI plants and would be expected to lead to better regeneration of the electrode, improved desalination performance and, potentially, a significant reduction in the need for use of clean-in-place procedures.

Development of sulfate-based smart water for improving the oil recovery from the calcite formation: New insights from molecular simulation

Wettability plays a huge role in the process of oil displacements, particularly in highly complex oil-wet carbonate reservoirs. Recently, sulfate ions were witnessed to have a great potency to alter the wetting state of calcite. Though the role of sulfate ion studied extensively, still the mechanism of their wettability modification is yet to be fully understood. It is expected due to the complex surface chemistry of rock in the presence of monovalent and divalent ions. In this study, we constructed a rock-oil-brine model at a molecular level and run the simulation on the wettability dynamics with various ions. The most abundant surface structure of calcite {1014}, was considered for this atomistic simulations. The model oil consisted of n-heptane and 10% octanoate ion as a polar component and sulfate-based salts were used as smart water. Two distinct hydration layers were found on the calcite surface. The contact angle measurements were made to find the effectiveness of smart water solutions in altering the wettability of the surface. Monovalent cations were observed to form a strong electric-double-layer while the divalent cations were preferred to get distributed in the bulk; most of them were attached to polar oil ions removing them from the calcite surface thus changing the wettability.

Adsorption of Mono- and Divalent Ions onto Dendritic Polyglycerol Sulfate (dPGS) as Studied Using Isothermal Titration Calorimetry.

The effective charge of highly charged polyelectrolytes is significantly lowered by a condensation of counterions. This effect is more pronounced for divalent ions. Here we present a study of the counterion condensation to dendritic polyglycerol sulfate (dPGS) that consists of a hydrophilic dendritic scaffold onto which sulfate groups are appended. The interactions between the dPGS and divalent ions (Mg2+ and Ca2+) were analyzed using isothermal titration calorimetry (ITC) and showed no ion specificity upon binding, but clear competition between the monovalent and divalent ions. Our findings, in line with the latest theoretical studies, demonstrate that a large fraction of the monovalent ions is sequentially replaced with the divalent ions.