Increase In Ion Concentration Research Articles

Nanoscopic Supercapacitance Elucidations of the Graphene-Ionic Interface with Suspended/Supported Graphene in Different Ionic Solutions.

Graphene-based supercapacitors have gained significant attention due to their exceptional energy storage capabilities. Despite numerous research efforts trying to improve the performance, the challenge of experimentally elucidating the nanoscale-interface molecular characteristics still needs to be tackled for device optimizations in commercial applications. To address this, we have conducted a series of experiments using substrate-free graphene field-effect transistors (SF-GFETs) and oxide-supported graphene field-effect transistors (OS-GFETs) to elucidate the graphene-electrolyte interfacial arrangement and corresponding capacitance under different surface potential states and ionic concentration environments. For SF-GFET, we observed that the hysteresis of the Dirac point changes from 0.32 to -0.06 V as the ionic concentration increases. Moreover, it results in the interfacial capacitance changing from 4 to 2 F/g. For OS-GFET, the hysteresis of the Dirac point remains negative (-0.15 to -0.07 V). Furthermore, the corresponding capacitance of OS-GFET decreases (53-16 F/g) as the ionic concentration increases. These suggest that the orderly oriented water structure at the graphene-water interface is gradually replaced by ionic hydration clusters and results in the difference of capacitance. The relationship between Dirac-point hysteresis value and ionic concentration can be modeled by using the first-order Hill equation to obtain the half occupation value (K = 1.0131 × 10-4 for KCl solution and K = 6.6237 × 10-5 for MgCl2 solution). This also agrees with the variances of two minerals in ion hydration within the inner water layer at the interface. This work illustrates the influence of interfacial nanoscale arrangement on interface capacitance formation and layout implications for the development of supercapacitors.

Antiferroelectric Order in Nematic Liquids: Flexoelectricity Versus Electrostatics.

The recent discovery of ferroelectric nematic liquid crystalline phases marks a major breakthrough in soft matter research. An intermediate phase, often observed between the nonpolar and the ferroelectric nematic phase, shows a distinct antiferroelectric response to electric fields. However, its structure and formation mechanisms remain debated, with flexoelectric and electrostatics effects proposed as competing mechanisms. By controlling the magnitude of electrostatic forces through ion addition in two representative ferroelectric nematic materials, it is shown that the primary mechanism for the emergence of antiferroelectric order is the flexoelectric coupling between electric polarization and splay deformation of the nematic director. The addition of ions significantly expands the temperature range over which the antiferroelectric phase is observed, with this range increasing with increasing ion concentration. Polarizing optical microscopy studies and second harmonic generation (SHG) microscopy reveal the splayed structure modulated in 2D, while SHG interferometry confirms its antiferroelectric character. The model previously used to describe pretransitional behavior is extended by incorporating the electrostatic contribution of ions. The model shows qualitative agreement with the experiments, accurately reproducing the phase diagram and temperature-dependent evolution of the modulation period of the observed structure.

Charge Arrangement Determines the Sensitivity of Aggregation Patterns between Peptide-Chains to the Surrounding Ionic Environment.

The molecular basis for the liquid-liquid phase separation (LLPS) behavior of various biomolecular components in the cell is the formation of multivalent and low-affinity interactions. When the content of these components exceeds a certain critical concentration, the molecules will spontaneously coalesce to form a new liquid phase; i.e., LLPS occurs. Intrinsically disordered proteins (IDPs) are usually rich in amino acids with charged side-chains, and thus, LLPS-involving interactions between their side-chains are of great interest. However, the molecular details of the coalescence of such charged IDPs in a salt solution are still lacking. Here, we focus on two types of peptide-chains with oppositely charged amino acids in extreme arrangements and investigate their aggregation patterns in various ionic environments. The results show that the interaction patterns between peptide-chains with nonuniform charge arrangement sequences are more sensitive to the surrounding cationic environment, and Na+ ions are more likely to cause aggregation of ASP residues compared to Mg2+ ions. As the ionic concentration increases, the electrostatic interactions between oppositely charged residues are gradually converted into a negative-negative amino acid interaction network bridged by Na+ ions, while the positive charge-rich regions are more strongly inclined to be exposed to the solvent environment and gain greater freedom of movement. Simultaneously, this effect will reach saturation with a further increase of salt concentration. The present study enriches insights into the electrostatic dominant factors in phase separation phenomena at the atomic level, which will hopefully inspire the design and application of targeted LLPS in the future.

Sorption of tetracycline antibiotics by microplastics, associated mechanisms, and risk assessments.

In this study, we selected polyvinyl chloride (PVC), polyethylene (PE), and polystyrene (PS) as representative microplastics (MPs) to systematically investigate the sorption behavior of tetracycline (TC) antibiotics by MPs. Scanning electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, and adsorption experiments were applied to assess the sorption behavior of MPs. The results demonstrated that the sorption of TC by MPs was most favorable under neutral conditions, where a modest increase in the salt ion concentration enhanced the adsorption of TC by MPs. The saturation adsorption capacities for PVC, PE, and PS for TC were determined as 121.95μg/g, 81.301μg/g, and 178.57μg/g, respectively. The strength of TC sorption by MPs followed the order of: PS>PVC>PE. Analysis of the sorption behavior of TC by MPs showed that the adsorption of TC by PE was weak and it readily desorbed, and thus their interaction will not lead to excessive compound pollution. By contrast, the adsorption of TC was high by PVC and PS, and they were not readily desorbed.

Preparation of (Ba0.25Ca0.25Sr0.25La0.25)Ti1-xAlxO3 High-Entropy Perovskite Ceramics for enhanced Microwave Dielectric Performance

Development of microwave dielectric ceramics with a high dielectric constant, high quality factor, and low temperature coefficient of resonant frequency is of great importance for achieving miniaturization, low loss, and high stability in microwave devices. Research on low dielectric constant microwave dielectric ceramics has made certain progress, but the development of new systems of high dielectric constant microwave dielectric ceramics with excellent overall performance is still in the exploratory stage. Herein, approaches of high-entropy strategy and small radius ions doping were combined to achieve high microwave dielectric properties. It is demonstrated that a high-entropy ceramic with a perovskite structure doped with Al3+ ion, denoted as (Ba0.25Ca0.25Sr0.25La0.25)Ti1-xAlxO3 (abbreviated as HESOs, 0<x≤0.25), was successfully synthesized. At x=0.1 and 1500oC, HESO exhibited optimized comprehensive dielectric performance, characterized by εr = 89.25, Q×f = 3304GHz, and τf = +361 ppm/oC. Besides, as the aluminum ion content increases, there is a reduction in grain size accompanied by an elevation in oxygen vacancy content, resulting in increase of Q×f, with a peak value reaching 4136GHz. This study presents a valuable exploration aimed at designing high-entropy perovskite ceramics with excellent dielectric properties.

Biosynthesis of Copper Nanoparticles by Cultures from Collection of Microorganisms

Biogenic production of copper nanoparticles by bacteria and fungi presents certain scientific and applied interest. In this regard, the ability to synthesize copper nanoparticles by microorganisms from the culture collection of the Institute of Microbiology, which were isolated from polluted areas, was studied. Twenty-one fungal strain and eight bacterial strains were screened, and the biosynthetic activity of representatives of Pseudomonas genus, as the most active biosynthetic of copper nanoparticles, was studied in a comparative aspect. The biosynthetic activity was determined 24-72 hours after adding standard solutions of CuSO4 of different concentration (25 – 50 mg/l by Cu++) to the culture liquid. The formation of nanoparticles was recorded by changing the color of the solution, as well as using UV spectroscopy and atomic force microscopy (AFM). Two strains of Fusarium oxysporum and one strain of Penicillium sp. were found to be the most active among the tested micromycetes. The formation of cubic copper nanoparticles and needle-like structures with a diameter of 800 nm and a length of 40 microns, which were formed as a result of aggregation of cubic nanoparticles with a size of 300-400 nm, has been established. All the tested bacteria showed the ability to synthesize copper nanoparticles, while Pseudomonas stutzeri and Pseudomonas sp. 23 strains expressed the greatest activity and obtained nanoparticles showed high stability. It was also noted that an increase in the initial concentration of copper ions in solution from 25 mg/l to 50 mg/l leads to an increase in the size of the resulting nanoparticles. Based on results of the UV-spectroscopy and AFM microscopy a database of microbial strains synthesizing copper nanoparticles was established, which may be used in future studies.

Oxidation of thiol groups in membrane proteins inhibits the fertilization ability and motility of sperm by suppressing calcium influx.

The redox state of thiol groups derived from cysteine residues in proteins regulates cellular functions. Changes in the redox state of thiol groups in the epididymis are involved in sperm maturation. Furthermore, the redox state of thiol groups in proteins changes during the process of sperm capacitation. However, the effect of the redox state of thiol groups in sperm membrane proteins on the fertilization ability of sperm has not been studied. Therefore, in this study, we oxidized thiol groups in sperm membrane proteins using 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB), which is a thiol-selective oxidizing agent, and examined the effect of oxidation of these thiol groups on the fertilization ability of sperm. Oocytes and sperm were obtained from C57BL/6J mice, and Jcl:ICR mice were used as recipients for embryo transfer. Oxidation of the thiol groups by DTNB decreased the in vitro fertilization rate, and removal of the zona pellucida recovered the fertilization rate. DTNB treatment decreased the amplitude of the lateral head, which is an indicator of hyperactivation, and suppressed an increase in the intracellular calcium ion concentration, which is essential for hyperactivation. These findings suggest that oxidation of thiol groups in sperm membrane proteins can decrease the fertility of sperm by suppressing calcium ion influx and hyperactivation.

Medium term hydrochemical and CO2 responses to anthropogenic and environmental changes in karst headwater streams.

This study investigates the intricate effects of lithology, temperature, discharge, and land use changes on headwater stream chemistry by analysing two decades of hydrochemical data from twenty karst headwater catchments in the Garonne River basin, France. Focused on the Pyrenees and the lowland (LM) and upland (UM) regions of the Massif Central, this study identified significant regional variations and commonalities in water chemistry. The headwater streams were clustered based on their hydrological and hydrochemical profiles, revealing strong similarities between upland sites, i.e. UM and Pyrenees, despite their geographical distance. The findings revealed a predominance of water driven by calcite dissolution, with specific influences from minor lithologies. Seasonal variations in water chemistry were primarily driven by hydrological conditions. Trend analyses highlighted increased pCO2 concentration in both the Pyrenees and UM, linked to higher forest density and agricultural activities, respectively. In contrast, LM exhibited increasing Ca2+ and HCO3- concentrations alongside decreasing trends in pCO2 and discharge, and increased nitrate concentration. While overall water temperatures increase, only a few sites exhibited significant warming trends, consistent with similar studies in the region and worldwide. These findings underscore the complex interplay between land use changes and hydrochemical dynamics in karst headwaters. They reveal that rising pCO2 concentration trends in upland regions are driven by reforestation and agricultural practices, which have significant implications in CO2 emissions, and consequently for regional and global carbon budgets and carbon-related policies. In lowland areas, declining water resources and increasing ion concentrations highlight potential challenges for water management, particularly in sensitive karst catchments. This study provides a baseline for understanding how karst headwaters respond to environmental changes. Expanding this research to other karst systems worldwide, under different climates, would help validate and model these findings, and improve our understanding of the global carbon cycle.

Evaluation of the Applicability of Rotating Cylindrical Anodes for Higher Speed Copper Electrolytic Refining

With the aim of increasing the overall speed of conventional copper smelting, in which a dry process and an aqueous electrolysis are connected in series, the challenge is to increase the speed of the electrolysis by increasing the current density, since the electrolysis is the rate-determining step in the series. However, electrolysis at high current density causes passivation of the anode due to a significant increase in the copper ion concentration near the anode, which inhibits electrolysis. The use of forced convection (stirring or jetting) has been considered to suppress passivation. However, it is not easy to apply the effect of forced convection uniformly across the electrode surface in the conventional electrolysis method, in which plate electrodes are arranged in a dense array. In this study, we proposed a method to obtain forced convection by rotating the cylindrical electrode (anode) as shown in the figure. The diffusion of copper ions from the anode surface can be promoted efficiently and uniformly by using this method. As a first step in the evaluation of the applicability, we performed numerical simulations of the tertiary current distribution to investigated the effects of the cylindrical anode rotation on the correspondence between the current density and the copper ion concentration near the anode. Figure 1

Metal ions released during canine retraction using fixed orthodontic appliance: Prospective clinical study

Background: Metal ions released from dental alloys pose a significant concern due to their potential local and systemic effects. One of these effects is hypersensitivity, particularly associated with nickel-containing dental alloys. Aims: to measure metal ion concen-tration in saliva during orthodontic space closure on a 0.019X0.025 working archwire. Material and Methods: Trial design: Con-trolled clinical trial. Setting: Orthodontic treatment was provided at the Postgraduate Orthodontic Teaching Clinics and saliva testing was performed at the Faculty of Chemical Engineering/ Jordan University of Science and Technology (JUST). Methods Participants and interventions: Twenty-eight participants with bimaxillary proclination requiring extraction of all first premolar teeth participated in this study. Teeth alignment started with 0.014-inch nickel titanium (NiTi) archwire, then with a sequence of 0.018-inch, 0.016X0.022-inch, and 0.019X0.025-inch NiTi archwires, before 0.019X0.025-inch Stainless Steel (SS) rectangular archwire was reached. Patients were monitored monthly for a period of three months. Three unstimulated saliva samples were collected from each patient; before the commencement of treatment (T0), when 0.019X0.25-inch SS archwire was reached before space closure (T1), and one month after space closure (T2). Ion concentration in saliva samples was measured using an inductively coupled plasma mass spectrometer (ICP-MS). Results: Before treatment, iron concentration (53 Fe and 54 Fe) averaged 197.05 (64.35) mg/L and 425.48 (164.43) mg/L, respectively. Iron concentration increased during the alignment stage of orthodontic treatment (P&lt;0.05) with no sig-nificant increase during space closure (P&gt;0.05). Other investigated ions (Cr, Co, Ni, and Ti) did not show significant changes during orthodontic treatment (P&gt;0.05). Conclusions: There was no increase in the metal ions concentration (Fe, Cr, Ti, and Ni) during space closure using a 0.019X0.025 working archwire and the Fe ion concentration increased in the initial stages of orthodontic treatment

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.

Optimizing photocatalysis: Tuning europium concentration in zinc oxide nanoparticles for superior performance

This work reports, improved photo catalytic performance of ZnO by band gap engineering via Eu doping (0.5–2.0 %). Single phase wurtzite structure of sol gel derived ZnO and Eu (0.5–2.0 %) doped ZnO are confirmed by XRD, FTIR and Raman spectra. Slight variation in structural parameter, FTIR stretching mode at 677 cm−1 and Raman E2 peak position indicate substitution of Eu+3 in ZnO. Calculated band gap decreases [3.05-2.89] with Eu concentration due to generation of charge trap level. Dye degradation of MO improved in Eu doped ZnO as compare to ZnO. The catalytic effectiveness is clearly shown by significant breakdown of a commonly used MO dye (at a concentration of 120 mg l−1). ZnO: Eu 2 % has a remarkable clearance rate of 99.37 %, which is explained by pseudo-first-order kinetics. The increase in oxygen radical ion concentration due to presence of Eu2O3 impurity phase in Eu 2 % doped ZnO supports MO degradation mechanism.

Microstructural Evaluation and Linkage to the Engineering Properties of Metal-Ion-Contaminated Clay.

The rapid progress of urbanization and industrialization has led to the accumulation of large amounts of metal ions in the environment. These metal ions are adsorbed onto the negatively charged surfaces of clay particles, altering the total surface charge, double-layer thickness, and chemical bonds between the particles, which in turn affects the interactions between them. This causes changes in the microstructure, such as particle rearrangement and pore morphology adjustments, ultimately altering the mechanical behavior of the soil and reducing its stability. This study explores the effects of four common metal ions, including monovalent alkali metal ions (Na+, K+) and divalent heavy metal ions (Pb2+, Zn2+), with a focus on how ion valence and concentration impact the soil's microstructure and mechanical properties. Microstructural tests show that metal ion incorporation reduces particle size, increases clay content, and transforms the structure from layered to honeycomb-like. Small pores decrease while large pores dominate, reducing the specific surface area and pore volume, while the average pore size increases. Although cation exchange capacity decreases, cation adsorption density per unit surface area increases. Monovalent ions primarily disperse the soil structure, while divalent ions induce coagulation. Macro-mechanical tests reveal that metal ion contamination reduces porosity under loading, with compressibility rises as the ion concentration increases. Soils contaminated with alkali metal ions shows higher compression coefficients at all loads, while heavy metal ions cause higher compression under lower loads. Shear strength, the internal friction angle, and cohesion in metal-ion-contaminated clay decrease compared to uncontaminated field-state clay, with greater declines at higher ion concentrations. The Micropore Morphology Index and hydro-pore structural parameter effectively characterize both micro- and macrostructural properties, establishing a quantitative relationship between HPSP and the engineering properties of metal-ion-contaminated clay.

A new spectrophotometric method for measuring ceruloplasmin ferroxidase activity: an innovative approach.

Ferroxidases are enzymes that participate in the iron metabolism of different organisms. They catalyze the oxidation of ferrous iron, Fe2⁺, into ferric iron, Fe3⁺, which is essential in iron homeostasis and physiological functioning. The present study describes a novel spectrophotometric method of serum ceruloplasmin ferroxidase activity. This method is easy to perform; it is also sensitive, specific, and rapid. In this method, ferrous ions are used as a substrate for the enzyme, with either salicylic acid or sulfosalicylic acid being taken as a chromogenic compound. These chromogens easily form a colored complex with ferric ions but are not formed with ferrous ions. In the enzymatic reaction, the ceruloplasmin ferroxidase enzyme catalyzes the oxidation of ferrous to ferric ions. The resulting increase in ferric ion concentration is then measured spectrophotometrically, following the formation of the colored complex. The complex formed has maximum absorbance at 540 nm in the case of salicylic acid and 490 nm in the case of sulfosalicylic acid. Comparatively, it was tested against the standard method to ascertain the new method's effectuality and reliability for assaying ferroxidase activity. The determined correlation coefficient amounted to 0.99, showing a strong correlation between the results obtained by the two methods. This new spectrophotometric technique offers a simplified, sensitive, specific, and fast means of estimating ferroxidase activity. It avoids using concentrated strong acids in the procedure and correlates excellently with the standard technique. This sets up a potential alternative for accurately determining ferroxidase activity in biological samples.

Spatio-temporal and depth-oriented evaluation of hyporheic zone processes in headwater catchments

The hyporheic zone (HZ) is vital for nutrient cycling and overall stream ecosystem health across groundwater-surface water interfaces, with biogeochemical and physical variations influencing exchange processes. To gain a depth-oriented insight into the various hyporheic functioning, isotopic (18O and 2H) and chemical analyses, along with physical parameters, were performed in two streams named Ahna and Losse in North Hesse, Germany. Multi-level interstitial probes were installed to extract subsurface pore water samples up to 0.45 m depth. We identified three distinct HZ in Ahna upstream, downstream and Losse. The Ahna upstream HZ was a less permeable barrier with low water fluxes but reactive, while the downstream HZ was less reactive with higher permeability and vertical fluxes. The Losse HZ, remained non-reactive but well-mixed with good hydraulic circulation due to fast downward flows. Isotopic composition revealed distinctive features, indicating increased evaporation and intricate mixing with other water sources and intensified subsurface flow in Ahna downstream compared to upstream. Hydro-chemical dynamics in Ahna exposed increased ion concentrations downstream, driven by anthropogenic factors along the course. Upstream denitrification was dominant under low oxygen conditions due to the slow infiltration and low mixing rates. The primary water source for both streams and HZs was groundwater, with the potential for rainwater to serve as a secondary source. This study shows the spatial heterogeneity of HZ processes and highlights that the specific HZ conditions need to be examined locally.

Propensity of hydroxide and hydronium ions for the air-water and graphene-water interfaces from abinitio and force field simulations.

Understanding acids and bases at interfaces is relevant for a range of applications from environmental chemistry to energy storage. We present combined abinitio and force-field molecular dynamics simulations of hydrochloric acid and sodium hydroxide highly concentrated electrolytes at the interface with air and graphene. In agreement with surface tension measurements at the air-water interface, we find that HCl presents an ionic surface excess, while NaOH displays an ionic surface depletion, for both interfaces. We further show that graphene becomes less hydrophilic as the water ions concentration increases, with a transition to being hydrophobic for highly basic solutions. For HCl, we observe that hydronium adsorbs to both interfaces and orients strongly toward the water phase, due to the hydrogen bonding behavior of hydronium ions, which donate three hydrogen bonds to bulk water molecules when adsorbed at the interface. For NaOH, we observe density peaks of strongly oriented hydroxide ions at the interface with air and graphene. To extrapolate our results from concentrated electrolytes to dilute solutions, we perform single ion-pair abinitio simulations, as well as develop force-field parameters for ions and graphene that reproduce the density profiles at high concentrations. We find the behavior of hydronium ions to be rather independent of concentration. For NaOH electrolytes, the force-field simulations of dilute NaOH solutions suggest no hydroxide adsorption but some adsorption at high concentrations. For both interfaces, we predict that the surface potential is positive for HCl and close to neutral for NaOH.

Coupling effect of concrete cracks and stray current on chloride-induced corrosion of rebar

Either concrete cracking or stray current promotes the corrosion of rebars; however, the coupling effects of concrete cracking and stray current on the rebar corrosion are still unknown. In this work, the effect of concrete cracking patterns coupled with stray current on rebar corrosion is presented by both experimental and finite element simulation. Specifically, there is a strong coupling effect when crack width is less than 100 μm, which manifests that ion concentration and electric field intensity increase pronouncedly with decreasing crack width. Simulation shows that the coupling effect leads to an asymmetric distribution of ions and electric fields at the crack tip, which in turn causes the asymmetric corrosion of rebars. Under the coupling effect, the highest corrosion rate reaches 3 μA/cm2 and is more than three times higher than that in a natural environment. Our findings contribute to understanding and evaluating accurately rebar corrosion in practical application.

Effect of environmental factors on adsorption of ciprofloxacin from wastewater by microwave alkali modified fly ash

Antibiotics, as emerging persistent pollutants, pose significant threats to human health. The effective and low-cost removal of ciprofloxacin (CIP) from wastewater has become an important research focus. In this study, fly ash (FA) was used as the raw material, and modified fly ash (MFA) was prepared by varying microwave power, alkali concentration, and immersion time to investigate its adsorption characteristics for CIP. Results showed that the optimal preparation conditions for MFA with the most effective adsorption of CIP, using the Box-Behnken response surface methodology, were a microwave power of 480 W, an alkali concentration of 1.5 mol/L, and a modification time of 3 h. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analyses revealed that after modification, the glassy structure of FA is destroyed, the specific surface area is increased, and obvious hydroxyl O–H absorption peaks appear. Both FA and MFA exhibited adsorption processes for CIP that conformed to pseudo-second-order kinetics and the Langmuir equation. Maximum adsorption of CIP (9.61 and 12.67 mg/g) was achieved at pH = 6. With increasing temperature, the adsorption capacity of both FA and MFA for CIP decreased, indicating an exothermic process. The adsorption capacity of CIP decreased with increasing ion concentration, with the impact order of ions being Al3+ > Ca2+ > Na+. The results show that pore filling, electrostatic interaction, ion exchange and complexation are the main ways of CIP adsorption by FA. Microwave alkali modified fly ash is an economical and efficient adsorbent for CIP removal in water, realizing the purpose of “treating waste with waste”. This study provides a scientific basis for controlling CIP treatment in wastewater.

Experimental study on freezing temperature and its influencing factors of loess contaminated by heavy metals

This paper attempts to reveal the freezing temperature and its influencing factors of heavy metal-contaminated loess by adopting two cooling methods: fast and slow grading. As a result, Lanzhou loess was used as an experimental material to make polluted soil with varying heavy metal concentrations and initial water content. The pollutant elements included Zn, Ni, Cu, Cr, Cd, and Pb. The findings demonstrate that: 1) The slow cooling rate causes supercooling, jumping, and a progressive decrease in the temperature of the polluted soil. Different cooling methods have no obvious effect on freezing temperature. Furthermore, the freezing temperature of contaminated soil varies depending on its water content. The impact of increasing water content on freezing temperature is not evident; 2) The freezing temperature of loess decreases with the increase of heavy metal ion content. The freezing temperature of loess polluted by Zn, Ni and Cd ions decreased linearly with the increase of ion content. The influence of cations on the freezing temperature of loess is as follows: Zn2+> Ni2+> Cd2+> Cr3+> Pb2+> Cu2+. The influence order of anions is Cl− > SO42−; 3) The freezing temperature of loess containing heavy metal ions is about equal to the freezing temperature of the corresponding heavy metal solution plus the freezing temperature of loess itself. The freezing temperature of heavy metal-polluted loess follows the temperature superposition principle.

Enhanced oil recovery and mitigating challenges in sandstone oil reservoirs employing EDTA chelating agent/ seawater flooding

While low salinity water (LSW) holds promise for improving oil recovery, its implementation is comparatively costly due to the substantial volumes of fresh water required to dilute seawater (SW). Additionally, concerns arise regarding potential issues related to LSW, including fines migration in sandstone reservoirs and scale formation in carbonate reservoirs. Chelating agents can be introduced into undiluted SW to bind with metal ions, thereby lowering its salinity. This approach mimics the behavior of LSW injection while overcoming associated challenges. This study involves measuring oil/injected solution interfacial tension (IFT), evaluating sandstone surface wettability alteration, along with conducting different sand pack flooding scenarios using Ethylenediaminetetraacetic acid (EDTA) chelating agent. The aim was to comprehend the EDTA oil recovery mechanisms and determine the optimal concentration of EDTA that minimizes chemical consumption while maximizing oil recovery. The findings indicated that incorporating 5 wt% EDTA into SW significantly reduced IFT from 29.52 mN/m to 4.75 mN/m, making the oil nearly miscible in the solution. Moreover, wettability tests confirmed that a minimum EDTA concentration of 5 wt% is required to shift wettability from oil-wet to strongly water-wet conditions. Sand pack flooding experiments, on the other hand, further demonstrated that this optimized fluid system can potentially recover an additional 16.1 % of oil following SW flooding. Finally, inductively coupled plasma (ICP) analysis revealed a notable increase in metal ion concentration during EDTA flooding, indicating enhanced leaching of metals from the sandstone surface and improved wettability characteristics.