Increase In Ionic Strength Research Articles

Role of Ionic Strength in Solubility of Salts in India

Purpose: The aim of the study was to assess the role of ionic strength in solubility of salts in India. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: Ionic strength increases, the electrostatic interactions between oppositely charged ions in the salt and the surrounding ions in the solution are weakened, leading to changes in solubility. Higher ionic strength often results in greater solubility of salts due to the shielding effect, which reduces ion pairing and prevents precipitation. However, in some cases, extremely high ionic strength may lead to the "salting out" effect, where solubility decreases as ions compete for solvation. This relationship is essential in fields like chemistry and environmental science, where understanding solubility is crucial for processes such as crystallization and precipitation reactions. Implications to Theory, Practice and Policy: Debye-hückel theory, van’t hoff factor and colligative properties theory may be used to anchor future studies on the role of ionic strength in solubility of salts in India. Industries involved in chemical manufacturing and wastewater treatment should adopt protocols that account for ionic strength when designing their processes. Policymakers should establish regulatory frameworks that promote the inclusion of ionic strength considerations in environmental assessments.

Oxidative Dissolution and the Aggregation of Silver Nanoparticles in Drinking and Natural Waters: The Influence of the Medium on the Process Development.

Currently, there are quite a few data on the ways silver nanoparticles get into the aquatic environment, on their subsequent dissolution in water, and on the release of toxic Ag+ ions. Differences in the experimental conditions hinder the determination of the basic regularities of this process. In this study, the stages of oxidative dissolution of AgNPs were studied, starting from the formation of silver hydrosol in deaerated solution, the reaction of silver with oxygen and with drinking and natural waters, the analysis of intermediate species of the oxidized colloidal particles, and the subsequent particle aggregation and precipitation, by optical spectroscopy, DLS, TEM, STEM, and EDX. In the presence of oxygen, silver nanoparticles undergo oxidative dissolution, which gives Ag+ ions and results in the subsequent aggregation of nanoparticles. The carbonate hydrosol loses stability when mixed with waters of various origin. This is due to the destruction of the electric double layer, which is caused by an increase in the solution's ionic strength and the neutralization of the charge of the metal core. The environmental hazard of the silver nanoparticle hydrosol would noticeably change and/or decrease when the nanoparticles get into natural waters because of their fast precipitation and because the major part of released Ag+ ions form poorly soluble salts with ions present in water.

Bactericide adsorption by purple soil modified by decomposed liquid and humic substance from Bischofia javanica

To investigate the effect of plant decomposition products on bactericide adsorption, purple soil (P) was modified using different ratios of decomposed liquid (Dl) and humic substance (Hs) from Bischofia javanica. Isothermal adsorption characteristics of fenaminosulf and hymexazol by different Dl- and Hs-modified Ps (Dl-P and Hs–P) were studied using the batch method. The effects of pH, ionic strength, and temperature on bactericides adsorption were analyzed. The adsorption process of fenaminosulf and hymexazol on modified Ps was suitable to be described by the Freundlich model. Meanwhile, the adsorption capacity of two bactericides on Hs-Ps was higher than that on Dl-Ps. Acidic conditions and low temperatures were more favorable for the adsorption of fenaminosulf and hymexazol on modified Ps. The adsorption amount of fenaminosulf increased first and then decreased, but that of hymexazol decreased with the increase in ionic strength. The adsorption process of two bactericides was a spontaneous, exothermic entropy-increasing reaction, and the physical adsorption mechanism mainly controlled the adsorption rate. In conclusion, Dl-Ps and Hs-Ps showed potential environmental remediation applications.

Adsorption characteristics and mechanisms of individual and a quinary mixture of heavy metal ions on novel CoFe2O4-BiFeO3 nanosorbents in water

Application of CoFe2O4-BiFeO3 nanocomposites (CFO-BFO NCs) in highly adsorptive removal of heavy metal ions (Pb(II), Co(II), Cu(II), Cd(II) and Zn(II)) by individual and simultanoeous adsorption were investigated for the first time in the present study. The characterization of CFO-BFO NCs were analyzed by using XRD, VSM, SEM, TEM and BET techniques. The CFO-BFO NCs powder consists of characteristic peaks of BFO and CFO without any trace of other crystalline phases; they were uniformly dispersed with a size of about 3–5 nm, much smaller than single – phase CFO (10–25 nm) and BFO (5–10 µm) with the surface area of 84.93 m2/g; remanence and coercivity were 14.33 emu/g, 1.99 emu/g and 195 Oe, respectively, significantly decreased compared to CFO but significantly increased compared to BFO. The single or simultaneous adsorption of a quinary mixture of Pb(II), Co(II), Cu(II), Cd(II) and Zn(II) on CFO-BFO NCs followed the Freundlich isotherm model and the pseudo-second-order kinetic model. Adsorption capacity of single heavy metal ions were in the order Pb(II) > Co(II) > Cu(II) > Cd(II) > Zn(II) while the simultaneous adsorption was in the order Pb(II) > Cu(II) > Co(II) > Zn(II) > Cd(II). The maximum adsorption capacities (qmax) of each ion in the case of simultaneous adsorption were smaller than that for cases of the single adsorption but the total qmax of ions mixture was much higher than the highest qmax of single adsorption. The simultaneous adsorption of heavy metal ions is the competition, the best selectivity is Pb(II) and the strongest competition is Cd(II), the adsorption ability reduces as the charge and radius of interfering cation increase and the ionic strength increases. The regeneration and reuse ability were good, while the adsorption efficiency slightly decreased over three recycles. The adsorption increased slightly as temperature increased. The adsorption process was spontaneous and endothermic. Adsorption of heavy metal ions on CFO-BFO NCs consists of both electrostatic and chemisorption. The applicability for real sample is good. Our results demonstrate that the CFO-BFO NCs is a prospective adsorbent to remove Pb(II), Co(II), Cu(II), Cd(II) and Zn(II) from aqueous environment.

Interaction between reacetylated chitosan and albumin in alcalescent media

Interaction of chitosan and its derivatives with proteins of animal blood at blood pH relevant conditions is of a particular interest for construction of antimicrobial chitosan/protein-based drug delivery systems. In this work, the interaction of a series of N-reacetylated oligochitosans (RA-CHI) having Mw of 10–12 kDa and differing in the degree of acetylation (DA 19, 24, and 40 %) with bovine serum albumin (BSA) in alkalescent media is described in first. It is shown that RA-CHI forms soluble complexes with BSA in solutions with pH 7.4 and a low ionic strength. Light scattering study shows that soluble RA-CHI complexes have spherical form with the radius of about 100 nm. Circular dichroism, fluorescent spectroscopy, and micro-IR spectroscopy studies show that the secondary structure of BSA in soluble complexes remain intact. Isothermal titration calorimetry of RA-CHI with DA 24 % and BSA mixing in the buffers with different ionization heats reveals a significant contribution of electrostatic forces to the binding process and an additional ionization of chitosan due to the proton transfer from the buffer substance. An increase of ionic strength to the blood relevant value 0.15 M suppresses the binding. It is shown that application of RA-CHI with higher DA value leads to a decrease in the affinity of RA-CHI to BSA and an alteration of the interaction mechanism. The finding opens an opportunity to the application of N-reacetylated chitosan derivatives in the complex systems compatible with blood plasma proteins.

Performance Evaluation of a Romanian Zeolite: A Sustainable Material for Removing Ammonium Ions from Water

Ammonium ion is a chemical species that is found in abundance in natural waters, whether underground or surface, but also in wastewater resulting from agricultural and industrial activities. Even if the removal of the ammonium ion from water has been studied for a very long time, it has been found that its removal is far from being solved. In this study, we evaluated the performance of the ammonium ion adsorption process on two adsorbents, zeolite clinoptilolite, ZR, a sustainable material (manufacturer: Zeolite Development SRL, Rupea, Brasov, Romania), and the other granular activated carbon type, Norit GAC 830 W. Zeolite ZR is found in very large deposits in Romania; it is a natural, cheap material with costs between 50 and 100 EUR/ton, compared to other adsorbents that cost over 500 EUR/ton and which can be regenerated and reused in the technological process of water treatment and purification, but also after exhaustion, as an amendment for the soil. In the first step, this paper presents the mineralogic (XRD) and structural (SEM and EDX) characterization of the ZR and the determination of the pH zero-point charge, pHZPC, for all the adsorbents. Studies were carried out in equilibrium and kinetic conditions. The efficiency of the adsorbent was investigated in different experimental conditions by varying the initial concentration, particle size, temperature, pH, ionic strength, and contact time. The mathematical models and parameters specific to the adsorption isotherms that best describe the experimental results were identified. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich mathematical models were used for comparison. The Langmuir isotherm proved to be the most appropriate to describe the adsorption of ammonium ions on all types of adsorbents used. The adsorption capacity of ammonium ions from synthetic solutions at 20 °C, pH = 6.09, for the range of initial concentrations 0–50 mg/L for Rupea zeolite is in the range of 10.46 mg/g−12.34 mg/g, and for granular activated carbon GAC W830, it is 16.64 mg/g. It was found that the adsorption capacity of the ammonium ion on both activated carbon and zeolite increases with increasing temperature and pH. Also, it was observed that as the ionic strength increases, the adsorption capacity decreases for all four adsorbents. Kinetic models were also identified that best describe the experimental processes. In this sense, pseudo-first order, pseudo-second order, intra-particle diffusion and the Elovich model were used. The results of the investigation showed that second-order kinetics governs the adsorption process on ZR, and pseudo-first order governs activated carbon.

Roles of Polymer Concentration and Ionic Strength in the Deposition of Chitosan of Fungal Origin onto Negatively Charged Surfaces.

This study examines the potential of fungal chitosan derived from Aspergillus niger as a sustainable alternative to traditional petrochemical-based ingredients in cosmetic products. Specifically, the research examines the solubility of fungal chitosan in aqueous solutions of varying ionic strength and its adsorption onto negatively charged surfaces that mimic human hair keratin. The adsorption behavior, water content, and frictional properties of chitosan films were evaluated using a quartz crystal microbalance with dissipation monitoring and a surface force apparatus (SFA). The findings indicated that fungal chitosan exhibits good solubility at a pH of 4.5. Conversely, the adsorption of chitosan is subject to the influence of both polymer concentration and ionic strength. At the lowest ionic strengths, a screening-enhanced adsorption process occurs as a consequence of the reduction in chitosan solubility in the presence of salt. This results in the depletion of polymer chains from the solution and their subsequent deposition. An increase in ionic strength above 15-20 mM results in a worsening of the chitosan-surface interaction, due to the simultaneous screening of both the chitosan and the surface charges. This results in a hindrance to the adsorption process. The deposited films are highly hydrated, and this hydration increases with both polymer concentration and ionic strength. Furthermore, the films exhibit a predominantly elastic behavior, and the response of the films under shear deformations shows a strong dependence on the polymer concentration. These findings contribute to the development of environmentally friendly cosmetic formulations that meet consumer demands for sustainability.

Application of biochar prepared from wheat bran as the binding phase in diffusive gradient in thin films technique for determination of mercury in natural waters

A novel binding gel for the DGT technique, containing biochar produced through the pyrolysis of wheat bran, was developed. The results of this study indicate that wheat bran biochar (WBBC) is a porous material with a surface area of 25 m2/g. The primary functional group on the surface of WBBC was identified as a carbonyl group, although some hydroxyl and imino groups were also detected. Furthermore, the findings demonstrate that the accumulation of Hg on WBBC was significantly influenced by an increase in ionic strength, particularly in NaCl solution, owing to Hg’s high affinity for chloride ions. The performance of the DGT with WBBC binding gel was also affected by solution pH, with the optimal pH for WBBC application falling within the range of 3–7. The diffusion coefficient of Hg, depending on the matrix environment, varied between 5.44 and 6.99 × 10−6 cm2/s. When applying the newly designed DGT technique to spiked samples of river water, an R value of 0.68 was achieved. The results of this work proved that modified DGT technique allows for a cost-effective analysis of Hg in natural waters with lower salinity, while retaining the fundamental properties of the binding gel incorporating a particulate adsorbent with anchored functional groups.Graphical

Ionic strength effect on the structure and dynamics of colloidal dispersions with weak attractive interactions

We present a macro- and microrheological study of the effect of ionic strength on the phase behavior, structure and flow properties of colloidal dispersions stabilized by short-range repulsive interactions inferred via co-polymerization of weak acid groups. We investigated the impact of ionic strength, by varying the concentration of natrium chloride (NaCl), on dispersions with only repulsive interactions, but also when additional attractive depletion forces are present due to added non-absorbent polymer, namely polyethyleneoxide (PEO). For dispersions with only repulsive electrosteric interactions, at low particle volume fractions (ϕ < 0.4), increasing ionic strength hardly affects the relative viscosity whereas at higher particle volume fractions, a decrease in viscosity is observed due to a reduced range of electrosteric repulsion between particles, corresponding to a reduction of the effective particle volume fraction ϕeff. For dispersions including attractive interactions, at volume fractions ϕ = 0.45 below the hard sphere freezing point (ϕc=0.5), independently of the ionic strength, the bulk viscosity increases monotonically with increasing PEO concentration due to the transition from a fluid to a fluid/crystalline and finally to a gel state. However, the increase in ionic strength shifts the concentrations of both phase transitions to lower polymer concentrations, indicating that in presence of salt a weaker attraction is required to induce these transitions. At ϕ=0.52, just above ϕc, for dispersions without added salt, broadening of the fluid-crystalline coexistence regime, due to added PEO, results in a viscosity minimum corresponding to different size and packing density of the crystalline regions as observed earlier in Weis et al. [1]. When salt is added, the initial state for dispersions without PEO is a fluid state due to the reduction of ϕeff and the addition of a small amount of PEO leads to an increase in bulk viscosity due to the formation of large crystals for dispersions containing 10 mM NaCl and a network of small, dense crystals of size ≈10 µm when 100 mM NaCl is added. At ϕ=0.54, a result similar to ϕ=0.52 is obtained for dispersions without added salt, whereas in presence of salt, we find that the fluid/crystalline coexistence regime narrows down as the range of electrosteric repulsion decreases and the addition of PEO results in gel formation and gels become more uniform with increasing attraction strength. These investigations demonstrate how superimposed short range electrosteric repulsion and weak depletion attraction affect microstructure and flow behavior of colloidal dispersions.

Effect of cation species on pressure-driven electrokinetic energy conversion in charged conical nanochannels

Electrokinetic energy conversion (EEC) offers a promising avenue for transforming elusive natural energy into electric power, showing a wide application spectrum. Unlike prevalent studies that chiefly utilize symmetrical electrolyte solution (e.g., KCl) and uniformly structured negatively charged nanochannels for EEC, this paper delves into a thorough examination of EEC characteristics—streaming current, streaming potential, and output power—in both positively and negatively charged conical nanochannels with symmetrical and asymmetric (CaCl2 and LaCl3) electrolytes solutions. Operating under the assumption that the electrolyte solutions (KCl, CaCl2, and LaCl3) possess equivalent ionic strength and, thereby, a common Debye length, our findings reveal a significant dependency of EEC characteristics and their regulation parameters on the electrolyte type, nanochannel charge polarity, and ionic strength. As the ionic strength increases, both the streaming current and output power initially rise to a peak before subsequently declining, with the ionic strength at the peak being influenced by the cation valence: lower valence leads to lower ionic strength. In asymmetric electrolyte scenarios, optimal EEC characteristic is observed in positively charged conical nanochannels under a reverse pressure difference, attributed to the ion-selective and ionic concentration distribution in the charged conical nanochannels. Moreover, the complex behaviors of the regulation parameters of EEC characteristics are unveiled. Notably, a tri-valent electrolyte's regulation parameters exceed those of a bi-valent electrolyte, indicating that ionic valence asymmetry enhances the regulation effects on EEC in conical nanochannels.

Internalization of PEI-based complexes in transient transfection of HEK293 cells is triggered by coalescence of membrane heparan sulfate proteoglycans like Glypican-4

Polymer-cationic mediated gene delivery is a well-stablished strategy of transient gene expression (TGE) in mammalian cell cultures. Nonetheless, its industrial implementation is hindered by the phenomenon known as cell density effect (CDE) that limits the cell density at which cultures can be efficiently transfected. The rise in personalized medicine and multiple cell and gene therapy approaches based on TGE, make more relevant to understand how to circumvent the CDE. A rational study upon DNA/PEI complex formation, stability and delivery during transfection of HEK293 cell cultures has been conducted, providing insights on the mechanisms for polyplexes uptake at low cell density and disruption at high cell density. DNA/PEI polyplexes were physiochemically characterized by coupling X-ray spectroscopy, confocal microscopy, cryo-transmission electron microscopy (TEM) and nuclear magnetic resonance (NMR). Our results showed that the ionic strength of polyplexes significantly increased upon their addition to exhausted media. This was reverted by depleting extracellular vesicles (EVs) from the media. The increase in ionic strength led to polyplex aggregation and prevented efficient cell transfection which could be counterbalanced by implementing a simple media replacement (MR) step before transfection. Inhibiting and labeling specific cell-surface proteoglycans (PGs) species revealed different roles of PGs in polyplexes uptake. Importantly, the polyplexes uptake process seemed to be triggered by a coalescence phenomenon of HSPG like glypican-4 around polyplex entry points. Ultimately, this study provides new insights into PEI-based cell transfection methodologies, enabling to enhance transient transfection and mitigate the cell density effect (CDE).

Condensed DNA incorporating mercaptoundecahydro-closo-dodecaborate (BSH) coated gold nanoparticles as a model system for boron neutron capture therapy (BNCT)

The experimental radiation therapy involving thermal neutron capture by boron (boron neutron capture therapy, BNCT) offers the advantage of high-LET ions with ranges on the order of a cell nucleus. Efforts to implement it have encountered serious difficulties. A practical model system would be able to address the underlying mechanisms of DNA damage and also calibrate Monte Carlo simulations. We describe the characterization of a plasmid-based model in which DNA condensed with a tetra-arginine peptide is co-aggregated with mercapto-closo-dodecaborate (BSH) coated gold nanoparticles (AuNPs). Condensed DNA is an excellent model for cellular chromatin, and the AuNPs are able to function as boron carriers and neutron dosimeters. Data from light scattering, UV–visible spectroscopy, fluorescence spectroscopy, sedimentation behavior, gel electrophoresis, and atomic force microscopy all indicate that the basic peptide acts to co-aggregate the two polyanionic species DNA and BSH-coated AuNPs. This aggregation is easily reversed by an increase in ionic strength to free the plasmid for subsequent assay. We argue that this three-component system is simpler, more convenient, and more flexible than other models requiring covalent attachments between DNA, boron, and/or gold.

Oxidation of tryptophan by benzimidazolium dichromate

In order to determine a likely mechanism, tryptophan oxidation with benzimidazolium dichromate (BIDC) in an acid medium utilizing sulfuric acid has been investigated at 313 K. First order dependence is demonstrated by the calculated pseudo-first order rate constant, which is found to be independent of the oxidant’s initial concentration. Additionally, the reaction exhibits first order behavior for both sulfuric acid and tryptophan. The rate of reaction is unaffected by an increase in ionic strength and is lowered by a decrease in the medium’s dielectric constant. Since acrylonitrile is not polymerizing, there is no chance of a free radical mechanism. The two electron transfers involved in the mechanism are confirmed when the concentration of manganous sulphate increases because it slows down the rate of reaction. A suitable mechanism and rate law have been derived from the experimental observations. The oxidation reaction yields carbon dioxide, ammonia, and indole-3-acetaldehyde as its products.

Spectroscopic monitoring of polyurethane-based nanocomposite as a potential catalyst for the reduction of dyes

In this study, AgNPs-loaded polyurethane-sodium alginate (PU-S/Alg) composite polymers were prepared by precipitation polymerization and in-situ reduction method. Their catalytic potential was evaluated for the reduction of methyl orange (MO), brilliant blue (BB), Rhodamine B (RhB), 4-nitroaniline (4-NA), and 4-nitrophenol (4-NP). Successful preparation of samples was confirmed by UV–Visible spectrophotometry (UV–Visible), Fourier transform infrared (FTIR), and Scanning electron microscopy (SEM) analysis. During the catalytic study, the value of kapp for the reduction of MO in the presence of NaBH4 and catalyst was found 0.488 min−1 while, in the presence of NaBH4 and catalyst alone, were found as 0.9 × 10-4 and 0.8 × 10-5 min−1, respectively which indicates the role of catalyst in making the reaction speedy. The value of kapp for the reduction of BB, RhB, 4-NA, and 4-NP was found as 0.764, 0.475, 0.212 and 0.757 min−1, respectively. Simultaneous reduction of dyes induced a decreased reaction completion time under the same reaction conditions. A slight increase in the value of kapp for the catalytic reduction of MO was also observed when reactions were performed in the presence of ionic media of different salts such as NaCl, KCl, CaCl2, and MnCl2. The rate of reduction of MO was increased with the increase in ionic strength of the medium. However, the presence of SDS (surfactant) in the reaction mixture induced the decreased activity of the catalyst and increased reaction completion time. The same value of kapp for the reduction of MO was observed in the case of freshly prepared and several days old nanocomposite catalyst. These results illustrate the stability and maintained catalytic potential of metal NPs for a prolonged time. Our reported catalyst also showed good potential for the treatment of dyes-polluted textile industry wastewater.

Factors influencing the increased 90Sr radioisotope migration in highly alkaline groundwater at Chornobyl NPP site

This paper analyses the formation of high Sr2+ concentration in strong alkaline (pH = 9.5–12.5) groundwater using data of the 27 years of observations around the destroyed Chernobyl NPP Unit 4. It appears that the formation of strong alkaline groundwater in different monitoring wells is consistent with the distribution of 90Sr, pH and main ions.The reason for the increase in 90Sr concentrations is the process of its migration from the sources of contamination - leaks of highly active water localized in certain premises inside the «Shelter » object.These computational experiments showed that for the groundwater in pH range 9.5–12.4, the concentration of strontium in the form of SrOH + increases and in the form of Sr2+ - decreases. In addition, the fraction of 90Sr in the form of a soluble neutral complex compound SrCO30, which is not sorbed, reaches 14–35%. Increased fractions of 90Sr in forms of SrOH+ and SrCO3 are factors which reduce the isotope ability to be sorbed by soils and therefore increase its migration ability. In strongly alkaline groundwater a sharp increase in 90Sr volumetric activity may also be caused by ionic strength (IS) increase above 5 mmol/L. Thus, the factors that influence the increase in 90Sr volumetric activity in strongly alkaline groundwater are the formation of its complex compounds and an increase in ionic strength (IS), which reduces the thickness of the double electric layer and, as a result, reduces the sorption capacity of soils.

INFLUENCE OF рН AND Ca&lt;sup&gt;2+&lt;/sup&gt; IONS ON CHEMICAL COMPOSITION AND SORPTION OF &lt;sup&gt;137&lt;/sup&gt;Cs BY CHERKASY BENTONITES (UKRAINE)

The safety of near-surface and deep radioactive waste storage facilities is based on a system of engineered and natural barriers. Significant degradation of the engineered barrier system composed of cemented waste matrixes covered by cement mixture, concrete compartments, and structures at the basement of the storage facility may cause radionuclide transfer from the facility to groundwater. Mixing of the cement and concrete with water leads to the formation of several various hydration products with subsequent leaching of Ca2+ ions and formation of hydroxyl ions (OH-), which affects the alkalinity of the water environment and the sorption properties of bentonite, as a component of the engineered barrier at the basement of near-surface facilities. The article presents the results of an experimental study of the influence of Ca2+ ion concentration and pH of the model solution (similar to groundwater composition at Vector Site in Chornobyl Exclusion Zone) on the elemental composition and sorption properties of natural (NB) and Na-modified (PBA-20) bentonites from the Cherkasy deposit concerning 137Cs at the Solid : Solution ratio of 1 : 100. Geochemical modeling suggests that addition of CaCl2 to test solution and resulting alkaline pH leads to precipitation of solids, mainly oxides, hydroxides, Fe oxyhydroxides (hematite, goethite, limonite), and Ca carbonates (calcite, aragonite, dolomite). Their role in Cs adsorption was evaluated. The concentration of structural elements (Si, Al) in bentonites practically does not change with Ca2+ ion concentration increase in the model solution, demonstrating the bentonite structure’s stability under these conditions. At the same time, an increase in the Ca concentration and a decrease in the Na concentration was found in the ion exchange complex of the bentonites if compared to the initial natural bentonite. This results in the transformation of Na-modified bentonite from Na, Ca-form to Ca, Na-form. The total sorption capacity of NB and PBA-20 bentonite concerning Cs+ ions at increased concentrations of Ca2+ ions and pH of the solution slightly decreases, though retaining high values of the degree of absorption (&gt; 90 %). The total adsorption of Cs+ ions on NB and PBA-20 bentonites from model groundwater with the addition of CaCl2 from 16 to 960 mg/dm3 and increase of рН from 7.4 to 11.8 decreases with the increase in ionic strength, in particular, due to competition with Са2+ and Na+ ions. NB and PBA-20 bentonites of the Cherkasy deposit remain a reliable component of the liner at the repository basement owing to their main functional property – high absorption capacity for 137Cs, which is an important dose-forming radionuclide of short-lived low- and medium-level waste.

The investigation of sorption-desorption performance and mechanism of copper by surfactant-modified zeolite in aqueous solutions.

As the most common filler in stormwater treatment, zeolite (NZ-Y) has good cation exchange capability and stabilization potential for the removal of heavy metal from aqueous solutions. In this study, sodium dodecyl sulfate (SDS) and NZ-Y were selected to preparing new adsorbent (SDS-NZ) by using a simple hydrothermal method. The sorption-desorption performance and mechanism of Cu(II) onto SDS-NZ were investigated. The results showed that the sorption of Cu(II) on SDS-NZ was in accordance with the pseudo-second-order kinetic model with an equilibrium time of 4h. The sorption behavior fitted Langmuir isotherm with a saturation sorption capability of 9.03mg/g, which was three times higher than that of NZ-Y. The modification of SDS increases the average pore size of NZ-Y by 3.96nm, which results in a richer internal pore structure and more useful sorption sites for Cu(II) sorption. There was a positive correlation between solution pH values and sorption capability of Cu(II) in the range of 3.0-6.0. With the ionic strength increased, the sorption capability of Cu(II) onto SDS-NZ first decreased and then increased, which may be attributed to competitive sorption and compression of the electronic layer. The desorption of Cu(II) on SDS-NZ was favored by the increase in SDS concentration and ionic strength and decrease in solution pH values. The application of SDS-NZ in runoff improved the leaching risk of Cu(II). After several cycles, the ability of reused SDS-NZ to efficiently adsorb most heavy metals was verified with removal rates above 99%.

Influence of water chemistry and operating parameters on PFOS/PFOA removal using rGO-nZVI nanohybrid

Graphene and zero-valent-iron based nanohybrid (rGO-nZVI NH) with oxidant H2O2 can remove perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) through adsorption-degradation in a controlled aquatic environment. In this study, we evaluated how and to what extent different environmental and operational parameters, such as initial PFAS concentration, H2O2 dose, pH, ionic strength, and natural organic matter (NOM), influenced the removal of PFOS and PFOA by rGO-nZVI. With the increase in initial PFAS concentration (from 0.4 to 50 ppm), pH (3 to 9), ionic strength (0 to 100 mM), and NOM (0 to 10 ppm), PFOS removal reduced by 20%, 30%, 2%, and 6%, respectively, while PFOA removal reduced by 54%, 76%, 11%, and 33% respectively. In contrast, PFOS and PFOA removal increased by 10% and 41%, respectively, with the increase in H2O2 (from 0 to 1 mM). Overall, the effect of changes in environmental and operational parameters was more pronounced for PFOA than PFOS. Mechanistically, •OH radical generation and availability showed a profound effect on PFOA removal. Also, the electrostatic interaction between rGO-nZVI NH and deprotonated PFAS compounds was another key factor for removal. Most importantly, our study confirms that rGO-nZVI in the presence of H2O2 can degrade both PFOS and PFOA to some extent by identifying the important by-products such as acetate, formate, and fluoride.

Tuning properties of phase-separated magnetic fluid with temperature

Phase-separated magnetic fluids provide a very strong magnetic response (μ>25) in a liquid state material. Even small fields can cause a notable material response, but this depends on its properties, which are often difficult to control. Here, we investigate how temperature affects the properties of the system, where phase separation is induced by an increase in ionic strength. Following the deformations of individual microscopic droplets, we can extract surface tension, magnetic permeability, and viscosity. We find that the temperature increase does not affect the surface tension, while the magnetic permeability and viscosity increase. Applying this knowledge to induce a shape instability for a drop only using temperature shows the potential of applicability of our findings.

Cd(II) and Pb(II) adsorption in karst soils amended with litter extract from Ficus virens

In this study, different proportions of Le were used to amend purple, yellow, and yellow–brown soils of karst areas to investigate the effect of litter extract (Le) from Ficus virens on Cd(II) and Pb(II) adsorption in karst soils. The basic physicochemical properties of Le-amended karst soils were determined, and the microscopic morphology of Le-amended karst soils was detected. The batch method was used to study the isothermal adsorption characteristics of Cd(II) and Pb(II) adsorption on different Le-amended karst soils. Physicochemical properties and microscopic morphology results showed that Le was amended on the karst soil surface and changed the surface properties of the karst soil. The maximum adsorption capacity range of Cd(II) and Pb(II) by Le-amended karst soils was 92.10–241.61 and 108.91–262.12 mmol/kg, respectively, and the peak value was reached when the karst soils were amended with 20 % of Le. Increasing the pH and temperature were beneficial to Cd(II) and Pb(II) adsorption in each Le-amended karst soil. The adsorption amount of Cd(II) and Pb(II) initially increased and thendecreased with the increase in ionic strength. Cd(II) and Pb(II) adsorption was a spontaneous, endothermic, and entropy-increasing process, and electrostatic attraction, precipitation, complexation, and ion exchange were the main adsorption mechanisms. The adsorption amount of Cd(II) and Pb(II) by Le-amended yellow–brown soil maintained approximately 85 % of original sample after three rounds of regeneration.