Ion Concentration In Solution Research Articles

Studies of the rate of gold sorption by the AM-2B anionite from cyanide-alkaline solutions

The paper presents the results of studies on the sorption leaching of gold-containing ore of the Vasilkovskoye deposit. Kinetic dependences of the sorption of gold and associated metals from cyanide-alkali solutions under different physical and chemical factors were obtained. It was found that gold on the AM-2B resin sorbed at a higher rate than, for example, copper and zinc. The solutions were analyzed using modern devices of a new generation: FT-IR spectrometer "Avatar 370". Laboratory studies were performed to determine the gold sorption rate by the AM-2B anionite from cyanide-alkaline solutions. It was found in the process of sorption of gold from multicomponent cyanide-alkali solutions on AM-2B anionite of mixed basicity, with the macroporous structure containing benzyl dimethylamine and dibenzyl dimethyl ammonium functional groups, that an important factor of qualitative and quantitative separation of gold and impurity metals is the concentration of cyanide and hydroxyl ions in solution. The temperature effect on the sorption rate of gold from cyanide-alkali solutions was studied with the temperature dependences F of t, Bt, of t, ln (l - F) of t, and D of t that show that the sorption process of dicyanoaurate ions is controlled by mixed diffusion.

Modeling and Optimization of Heavy Metals Biosorption by Low-Cost Sorbents Using Response Surface Methodology

This paper exploits, through modeling and optimization, the experimental laboratory data on the biosorption of heavy metal ions Pb(II), Cd(II), and Zn(II) from aqueous media using soybean and soybean waste biomasses. The biosorption modeling was performed using the Response Surface Methodology, followed by optimization based on numerical methods. The aim of the modeling was to establish the most probable mathematical relationship between the dependent variables (the biosorption efficiency of the biosorbents when adsorbing metal ions, R(%), and the biosorption capacity of sorbents, q(mg/g)) and the process parameters (pH; sorbent dose, DS (g/L); initial metal ion concentration in solution, c0 (mg/L); contact time, tc (min); temperature, T (°C)), validated by methodologies specific to the multiple regression analysis. Afterward, sets of solutions were obtained through optimization that correlate various values of the process parameters to maximize the objective function. These solutions also confirmed the performance of soybean waste biomass in the removal of heavy metal ions from polluted aqueous effluents. The results were validated experimentally.

Modified magnetic-metal organic framework as a green and efficient adsorbent for removal of heavy metals

A novel adsorbent was prepared for fast and selective removal of heavy metal ions Hg(II), Cd(II) and Pb(II). The adsorbent was simply prepared by immobilizing tripeptide glutathione on the surface of a magnetic metal-organic framework (Fe3O4-ZrMOF). The microcrystalline structure of ZrMOF provided a high surface area in an ordered structure for deposition of large amounts of glutathione. All measurements were performed by electrothermal atomic absorption spectroscopy (EAAS). Adsorbent structure was studied by using X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Fourier-transform infrared (FT-IR) spectroscopic methods, transmission electron microscopy (TEM), field emission-scanning electron microscopy (FE-SEM), Zeta potential measurement, and BET analysis. Computational modeling was used to obtain optimized structures for the adsorbent before and after binding to the heavy metals, which showed the most stable adduct for Hg attached to Fe3O4-ZrMOF@GSH (ΔGº = −1068.45 kJmol−1L−1). In removal procedure, the effective factors were discussed and optimized, such as the dosage of adsorbent, initial pH of solution, contact time, and initial concentration of metal ions. The maximum adsorption capacity (Qm) for Hg, Cd, and Pb was calculated to be 431, 393, and 397 (mg g−1), respectively. The proposed adsorbent was able to remove 95–99% of these ions from the solution, under optimum conditions in 20 min. Adsorption isotherm and kinetics for Hg(II), Cd(II), and Pb(II) on Fe3O4-ZrMOF@GSH were well described by Langmuir model and pseudo-second-order kinetics, respectively.

Comparison and Optimization of Operational Parameters in Removal of Heavy Metal Ions from Aqueous Solutions by Low-Cost Adsorbents

Removal of heavy metal ions such as cadmium, lead, chromium, and iron from industrial wastewater is one of the most critical environmental problems. In this research, natural and low-cost adsorbents like the tangerine peel, bovine gut, tea waste, and sunflower seed hull were used for adsorption of heavy metals, such as chromium and iron, from contaminated solutions. The effects of environmental factors such as contact time, pH, the amount of adsorbent dose, and the initial concentration of metal ions in synthetic solution were investigated to obtain optimal conditions for the adsorption of heavy metal ions. For separation of chromium metal ion from aqueous solution, tea waste, tangerine peel, bovine gut, and sunflower seeds hull showed adsorption capacity of 85%, 51%, 46%, and 34%, respectively, while for the adsorption of iron (III), the adsorption capacities of tea waste, bovine gut, tangerine peel, and sunflower seeds hull were 96%, 96%, and 87%, respectively. The adsorption isotherms were in decent correlation with the Langmuir and Freundlich isotherm models. The adsorption kinetics of iron and chromium has a proper validation with the pseudo-second-order kinetic model. The BET and FTIR analyses were also reported to investigate the adsorption properties. This study suggests these adsorbents as low-cost and economical materials for the adsorption of chromium and iron ions with a high adsorption rate.

Characteristics of cadmium translocation and isotope fractionation in Ricinus communis seedlings: Effects from split/cut-root and limited nutrients

Studying cadmium (Cd) transport in plants will improve the current understanding of Cd tolerance mechanisms. Due to the influence of analytical techniques, the application of Cd isotopes in plants is still in its early stages. Therefore, the relationships between Cd isotope fractionation and Cd translocation in plants remain unclear. In this study, we cultured Ricinus communis in hydroponic solutions during split/cut-root experiments and limited and infinite nutrient experiments. To understand the Cd transport process, the Cd2+ and other ion concentrations in different tissues (i.e., roots, stems, and leaves) and nutrient solutions, Cd isotope composition and the soluble protein in tissues were measured. The results showed that although significant effects were evident in the top leaves, the principal roots had less pronounced effects on Cd2+ translocation in the stems. Moreover, Cd underwent homolateral transport before it was translocated from the principal roots to the leaves on the side without Cd. It was apparent that the stems were responsible for translocating Cd2+ in plants. In addition, the continuous supply of high Cd2+ concentrations inhibited the growth of the top leaves, while in low Cd2+ concentrations, it was gradually transferred to the top leaves. Moreover, the tissues of R. communis were enriched with lighter Cd isotopes compared with the solutions. The clear differences between the Cd isotope fractionation of leaves under infinite and limited nutrient experiments may be attributed to plant growth and Cd uptake rates. This study provides important information for understanding Cd2+ translocation in R. communis and furthers our understanding of its tolerance and hyperaccumulation.

Programmable chemical actuator control of soluble and membrane-bound enzymatic catalysis.

Enzyme catalyzed reactions can be started, stopped, and throttled by regulating ion concentration in solution. The flow of charge through solution is related to the flow of electrons through an electric circuit using electrochemistry. However, current electrochemical methods to vary ionic concentration are largely limited to the electrode surface, making it impractical to exploit ionic concentration as a control variable in traditional enzyme assays. This chapter presents an electrochemical cell, termed a programmable chemical actuator (PCA), that uses selective electrochemical REDOX reactions to regulate the concentration of ions that control enzyme catalyzed reaction kinetics. The PCA is a polypyrrole polymerized and equilibrated to impart Mg2+, Mn2+, or OH- ion selectivity to working electrodes. Duplex pulse amperometry demonstrated reversible control over the pH-dependent kinetics of alkaline phosphatase, a soluble homodimeric enzyme, during a spectrophotometric assay. PCAs were also used to extend electrochemical control to the membrane-bound enzyme complex rubber transferase by modulating Mg2+ and Mn2+ concentrations during a radiometric enzyme assay. PCAs demonstrated tunable control over rubber transferase activity and rubber molecular weight without dislodging either the elongating rubber molecule or irreversibly inhibiting the rubber transferase complex. This chapter presents methods to fabricate and operate PCAs to facilitate insights into the roles of ions in biochemical pathways and environmental responses in plants.

Transformation of the coordination nanostructures of 4,4',4''-(1,3,5-triazine-2,4,6-triyl) tribenzoic acid molecules on HOPG triggered by the change in the concentration of metal ions.

The modulation effects of Cu2+/Fe3+ ions on the hydrogen-bonded structure of 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl) tribenzoic acid (TATB) on a HOPG surface have been investigated at the liquid–solid interface by scanning tunneling microscopy (STM). STM observations directly demonstrated that the self-assembled honeycomb network of TATB has been dramatically transformed after introducing CuCl2/FeCl3 with different concentrations. The metal–organic coordination structures are formed due to the incorporation of the Cu2+/Fe3+ ions. Interestingly, a Cu2+ ion remains coordinated to two COOH groups and only the number of COOH groups involved in coordination doubles when the concentration of Cu2+ ions doubled. A Fe3+ ion changes from coordination to three COOH groups to two COOH groups after increasing the concentration of Fe3+ ions in a mixed solution. Such results suggest that the self-assembled structures of TATB molecules formed by metal–ligand coordination bonds can be effectively adjusted by regulating the concentration of metal ions in a mixed solution, which has rarely been reported before. It explains that the regulatory effect of concentration leads to the diversity of molecular architectures dominated by coordination bonds.

Electrochemical Method of Lead (II) Ions Removal from Wastewater Using Granular Graphite Electrodes

The article presents an electrochemical method of wastewater treatment from Pb (II) ions through granular graphite electrodes. The cathode was made of graphite particles and the anode was made of rod graphite. Fea-tures of wastewater treatment from heavy metals by using developed surface granular graphite electrodes were revealed. Electrochemical research was carried out in a flow mode in a two-chamber electrolyzer. Effect of different electrochemical parameters (current density, electrolyte flow rate, initial concentration of lead (II) ions in solution, size of graphite granules, and concentration of additional cations in solution) to the reduction process of Pb (II) on lump graphite was studied. Results revealed that the removal value of Pb (II) hit a peak at 150A/m2 current density and gradually decreased at a higher value. The efficiency of electrolysis in the flow mode was demonstrated. It was found that the initial concentration of lead ions in the electrode process was insignificant, while the concentration of additional cations had a significant effect. Using very small par-ticles of granular graphite electrodes caused an agglomeration. At an optimal condition, (i=150 A/m2; V=150 ml/h; [Pb2+] = 200 mg/l; s= 0.05 cm3) treatment value of wastewater from Pb (II) ions reached 97.6±0.3 %.

Registration of small (below 1%) changes of calcium ion concentration in aqueous solutions and in serum by the constant potential coulometric method

Small changes (down to 0.1%) of Ca2+ ion activity in pure solutions of CaCl2, model solutions mimicking blood serum, and blood serum sample are registered by constant potential coulometric measurements, using solid contact ion-selective electrodes (ISEs) with poly(vinyl chloride) (PVC) membrane containing ETH 1001 as neutral ionophore. A new measurement protocol is proposed aimed at a significant improvement of the signal-to-noise ratio in the current measurements. A procedure is developed for the PEDOT-PSS deposition on glassy carbon from mixed water-acetonitrile solution. Data are obtained in support of Kragh-Hansen and Vorum’s approach for the quantification of the interaction between Ca2+ ions and bovine serum albumin (BSA).

Ion-selective Electrodes Based on PVC Membranes for Potentiometric Sensor Applications: A Review

Ion-selective electrodes (ISEs) are potentiometric sensors used to measure some of the most critical analytes in environmental laboratory. Recently ion sensors are taking place of various analytical techniques, as they provide a convenient and fast method of electroanalysis. Ion-selective electrodes are simple, relatively inexpensive, robust, durable, and ideal to be used for the detection of heavy metal ions. Important characterisctics of ISEs are selectivity, response time, detection limit, working range, effect of pH etc. Lot of research work is being done for the formation of ISEs by using polymeric membrane incorporated with ionophores or electroactive material. Various types of Schiff bases, macromolecules and metal complexes may be used as ionophores along with plasticizer, ion-excluder for the membrane preparation. Ion-selective electrodes will be optimized for pH range, selectivity, sensitivity, working concentration range and lifetime before their use as sensor electrode for determining the concentration of ions in solution. Various researchers are working in the field to develop Ion-selective electrodes which shows better selectivity and sensitivity than the previously reported electrodes and can be used as electrocatalysts. These ISEs can be used as electrochemical sensors for the analysis of food products, drinking water, beverages, fertilizers, and for the analysis of sample containing toxic substances.

Unexpected transformation of n.c.a. [111In]InCl3 in stock solutions into an unreactive [111In]In-species

While performing multiple indium-111 labeling of DOTA-modified peptides from a single batch of [111In]InCl3, inconsistent radiochemical yields were observed. We found that the formation of a radioactive impurity in the [111In]InCl3 stock solution hampered the reactivity of the indium-111 during radiolabeling reactions. The formation of this unknown 111In-species could be successfully suppressed by increasing the concentration of chloride ions in the stock solution and [111In]InCl3 was “recovered”. Radiolabeling of DOTA-peptides with the stabilized [111In]InCl3 resulted again in acceptable radiochemical yields. In addition, we report convenient iTLC systems that allow distinguishing between [111In]InCl3, the formed unknown 111In-species, radiocolloids, and radiolabeled peptides (DOTANOC).

Ammonium molybdophosphate/metal-organic framework composite as an effective adsorbent for capture of Rb+ and Cs+ from aqueous solution

A new composite adsorbent (AMP@MOF-76(Sm)) grafted ammonium molybdophosphate onto MOF-76(Sm) was synthesized via a solvothermal method and well-characterized by SEM-EDS, particle size analysis, N2 adsorption-desorption isotherms, TG, FT-IR, XRD and XPS analysis. The adsorption behaviors of Rb+ and Cs+ on synthesized AMP@MOF-76(Sm) were investigated depending on the parameters of solution pH, ionic strength, contact time, ion concentration and temperature. The adsorbent can adsorb Rb+ and Cs+ from the solution when the solution pH ranged from 4.0 to 10.0 and the coexisted ion (Na+) has little effect on the adsorption amounts of both Rb+ and Cs+. The adsorption kinetic data fitted well with pseudo-second order kinetic models. The adsorption equilibrium of Rb+ and Cs+ on AMP@MOF-76(Sm) is better explained by the Langmuir isotherm model and the maximum adsorption amounts for Rb+ and Cs+ are 0.490 ​mmol ​g−1 and 0.434 ​mmol ​g−1, respectively. Furthermore, the AMP@MOF-76(Sm) could be easily reused at least four times using 3.0 ​mmol ​L−1 ammonia nitrate as the eluent. The mechanism of the adsorption of Rb+ and Cs+ is proposed to be a combination of electrostatic attraction and ion exchange mechanism.

Molecular dynamics simulations of A-DNA in bivalent metal ions salt solution

A-form DNA is one of the biologically active double helical structure. The study of A-DNA structure has an extensive application for developing the field of DNA packaging in biotechnology. In aqueous solution, the A-DNA structure will have a free transformation, the A-DNA structure will be translated into B-form structure with the evolution of time, and eventually stabilized in the B-DNA structure. To explore the stability function of the bivalent metal ions on the A-DNA structure, a series of molecular dynamics simulations have been performed on the A-DNA of sequence (CCCGGCCGGG). The results show that bivalent metal ions (Mg2+, Zn2+, Ca2+) generate a great effect on the structural stability of A-DNA in the environment of high concentration. As the interaction between metal ions and electronegative DNA chains, the stability of A-DNA in solution is gradually improved with the increasing solution concentration of ions. In metal salt solution with high concentration, metal ions can be easily distributed in the solvation shells around the phosphate groups and further lead to the formation of shorter and more compact DNA structure. Also, under the condition of the same concentration and valency of the metal ions, the stability of A-DNA structure is different. The calculations indicate that the structure of A-DNA in CaCl2 solution is less stable than in MgCl2 and ZnCl2 solution.

Antibiofilm activity of nanosilver coatings against Staphylococcus aureus

Implant infections due to bacterial biofilms constitute a major healthcare challenge today. One way to address this clinical need is to modify the implant surface with an antimicrobial nanomaterial. Among such nanomaterials, nanosilver is arguably the most powerful one, due to its strong and broad antimicrobial activity. However, there is still a lack of understanding on how physicochemical characteristics of nanosilver coatings affect their antibiofilm activity. More specifically, the contributions of silver (Ag)+ ion-mediated vs. contact-based mechanisms to the observed antimicrobial activity are yet to be elucidated. To address this knowledge gap, we produce here nanosilver coatings on substrates by flame aerosol direct deposition that allows for facile control of the coating composition and Ag particle size. We systematically study the effect of (i) nanosilver content in composite Ag silica (SiO2) coatings from 0 (pure SiO2) up to 50 wt%, (ii) the Ag particle size and (iii) the coating thickness on the antibiofilm activity against Staphylococcus aureus (S. aureus), a clinically-relevant pathogen often present on the surface of surgically-installed implants. We show that the Ag+ ion concentration in solution largely drives the observed antibiofilm effect independently of Ag size and coating thickness. Furthermore, co-incubation of both pure SiO2 and nanosilver coatings in the same well also reveals that the antibiofilm effect stems predominantly from the released Ag+ ions, which is especially pronounced for coatings featuring the smallest Ag particle sizes, rather than direct bacterial contact inhibition. We also examine the biocompatibility of the developed nanosilver coatings in terms of pre-osteoblastic cell viability and proliferation, comparing it to that of pure SiO2. This study lays the foundation for the rational design of nanosilver-based antibiofilm implant coatings.

Recycling of residual valuable metals in cyanide-leached gold wastewater using the N263-TBP system

In this study, the synergistic extraction system of trioctylmethyl ammonium chloride (N263)-tributyl phosphate (TBP)-n-octanol-sulfonated kerosene was used to enrich and recover valuable metals from cyanide gold extraction of wastewater. The effects of the proportion of N263 and TBP, contact time, initial pH of water phase, temperature, and phase ratio (O/A) on the extraction percentage of metal cyanide complex ions and the synergistic extraction reaction mechanism were mainly investigated. Results showed that the single-stage extraction percentages of Cu, Zn, and Fe ions in wastewater were 99.87%, 99.8%, and 96.2%, respectively, and the saturated extraction capacity was 4356.4 mg/L under the conditions of N263 (20 vol%)-TBP (20 vol%)-n-octanol (10 vol%)-sulfonated kerosene system at 25 °C, O/A of 1:1, pH of 10, and contact time of 5 min. Fourier transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS) analyses showed that metals entered the organic phase in the form of metal cyanide complex ions during extraction. Metal cyanide complex ions preferentially combined with TBP to lose hydrophilicity and then reacted with N263 cations to enter the organic phase. The saturated organic phase was stripped by NaOH and NaSCN mixed solution, and the total concentration of metal ions in the stripping solution reached 11,996.6 mg/L.

Influence of carbonate coarse aggregate properties on surface resistivity of high performance concrete

Surface resistivity (SR) test measures the extent of ionic transport in cementitious systems. The present study sought to understand the influence of coarse aggregate type (limestone, dolostone), their chemical composition, and pore structure on the SR of high-performance concrete (HPC). In this study, water absorption and pore structure of five different coarse aggregates were measured. Concrete specimens were made with identical materials, mix proportions, and preparation methods, except for the difference in the sources of the coarse aggregates. Pore structure and SR of the concrete and the corresponding mortar were evaluated. The microstructures, especially the aggregate-paste interfaces, of the concrete were examined using scanning electron microscopy (SEM). The micromorphology of the specimens was also observed using thin section petrographic analysis. The results indicate that the SR of the concrete mixes decreased linearly (R2 >0.91) with the total porosity of all five coarse aggregate until 28 days. After 28 days, this trend no longer held likely due to the chemical interaction of dolostone aggregates with paste, while limestone aggregates did not react.SEM-backscatter (BSE) and SEM-secondary electron (SE) imaging coupledwithenergy dispersive X-ray spectroscopy(EDS)and thin section petrography suggested that dolostone aggregate-paste reactions resulted in precipitation of newer calcite deposits at aggregate-paste interfaces. This densified the interface and probably reduced the concentration of mobile ions in the pore solution within the concrete pore network resulting in higher SR after 28 days. Due to less stable nature of dolostone aggregates in highly alkaline conditions, HPC with dolostone aggregate also provided a conducive environment for the mineralization of secondary ettringite (calcium sulfoaluminate) within paste pore spaces. We contend that the greater SR gain by dolostone concrete mixes than that by limestone concretemixes in later ages is explained by the combination of the aggregate-paste interface densification, reduction in ionic concentration of the concrete pore solution, and secondary ettringite mineralization.

Fluorimetric Readout of Ion Selective Electrode Signals Operating under Chronopotentiometric Conditions

AbstractThe applicability of emission readout of ion‐selective electrodes, containing fluorimetrically active polyoctylthiophene in the membrane, operating under chronopotentiometric mode was studied. The electrochemical and optical signals were collected in the same experiment and compared. In both modes a change in recorded signal: potential or emission in time was observed while a constant current was applied to the sensor. The recorded signals (chronopotentiometric, fluoro‐chronopotentiometric curves and calculated transition times) were dependent on the concentration of potassium ions. The transition times calculated from electrochemical signals were linearly dependent on the concentration of potassium ions in solution within the range: 0.1–0.7 mM. Optically read transition times were also linearly dependent on concentration within the same range, however, they were shorter than those recorded electrochemically. This difference is attributed to various effects represented by the transition time: concentration increase of reduced form of the conducting polymer in the optical mode or depletion of potassium ions close to the membrane surface, in the electrochemical mode.

Fluoride Ion-Selective Electrode for Organic Solutions.

Fluoride ions are used in battery electrolytes in fluoride shuttle batteries. Since organic solvents are used in battery electrolytes, there is a growing demand to develop appropriate methods for quantifying fluoride ion concentration in organic solvents. In this study, a fluoride ion-selective electrode (ISE) for organic solutions is proposed as an electrode of the second kind. A Ag|AgF electrode was made via the anodization of a silver wire in propylene carbonate (PC) containing dissolved fluoride ions. The resultant electrode exhibits a stable linear response of the open circuit potential to the logarithm of the fluoride ion concentration in PC solutions over a range of 10-4-10-2 mol dm-3. The lower and upper limits of the linear response were interpreted in terms of the solubility and the formation of a silver fluoride complex. The use of this electrode of the second kind is suitable for the analysis of fluoride ions in organic solutions and is a promising concept for the development of ISEs for the detection of ions in organic solutions under highly restrictive conditions.

A Highly Selective and Interference-Resistive Opto-Mechatronic Sensor for Fast Detection of Nickel Ions

In this research, we developed an innovative, miniature, low-cost, and fast-response nickel ion photoelectric sensor system using the principle of light absorption characteristics described by Beer–Lambert’s law. We used the proposed ideas to analyze the absorption spectrum of nickel ions in aqueous solutions and selected a unique UV absorption band for these ions, and successfully fabricated an initial photoelectric sensor system. A quantitative study through the relationship between the concentration of nickel ions in the aqueous solution and the degree of light absorption was conducted. When other metal ions (such as Cd, Pb, Fe and Cl) co-exist, the nickel ion photoelectric sensor shows excellent selectivity and has sufficient linearity and good repeatability. The sensitivity of the originally designed photoelectric sensing system for Ni ions is 1.58 UVA intensity (A.U.)/ppm with excellent ion-selective characteristics and interference-resistant ability in terms of its complexity and fabrication cost.

A study of wastewater purification from Zn2 + ions by nanosorbent, obtained by electroerosion dispersion

Сurrent state and efficiency of existing sorbtion methods of industrial wastewater treatment are considered. The influence of important parameters for sorbtion process - ratio of metal ion and nanosorbent concentrations in solution, as well as the method of sorbent addition into wastewater on degree of its purification was studied. The most effective results of water purification were achieved with usage of freshly obtained powder of electroerosive dispersion (EED) of iron in water in the form of a suspension at ratio of the concentration of Zn2+ ions and nanosorbent powder 1:10. It Under such conditions a high degree of removing as 98% is determined, and obtained purified solution meets the standards of rising water at galvanic facilities, regarding of Zn2+ content.