Ion Concentration In Solution Research Articles

Catalytic activation of O2 by Al0-CNTs-Cu2O composite for Fenton-like degradation of sulfamerazine antibiotic at wide pH range

In this study, a novel Al°-CNTs-Cu2O composite, capable of activating O2 to generate H2O2 and further to reactive oxygen species (ROSs) at a wide pH range, was synthetized, characterized and applied for the degradation of sulfamerazine. In the activation of O2 by Al°-CNTs-Cu2O composite, H2O2 was generated from the reaction of O2 with Al°-CNTs, which could be catalytically decomposed into O2− and OH by Cu2O, the formed Cu(II) could be rapidly reduced to Cu2O by Al°-CNTs in composite, which made Al°-CNTs-Cu2O composite reusable and decreased the leaching of copper ions into solution. The removal efficiency of SMR and TOC was 73.91 % and 56.80 %, respectively at initial pH = 5.8, T = 20 °C, O2 flow rate = 100 mL/min, Al°-CNTs-Cu2O dosage = 2 g/L, SMR = 50 mg/L, and reaction time = 60 min. The removal efficiency of SMR kept almost unchanged and the concentration of copper ions in solution was below 0.5 mg/L. The Al°-CNTs-Cu2O/O2 process could be used as a novel catalyst for the degradation of refractory organic contaminants in water and wastewater by Fenton-like process at a wide pH range through the in situ generation of H2O2.

Effect of PbO on cyanidation leaching behavior of bornite

During the cyanidation of gold‑copper ores or concentrates, the presence of cyanide-soluble copper significantly increases the cyanide consumption. However, the consumption of cyanide and dissolved oxygen, the concentration of sulfide ions in the leaching solution decreased with the increase of PbO amount. The SEM-EDS analyzed that there was no obvious corrosion on the surface of the bornite leaching residue in the presence of 1.5 g/L PbO, but the surface was getting very sleek. It was known from thermodynamic calculation that PbO would partially dissolve to form plumbite ions in the alkaline cyanide solution, and plumbite ions would react with sulfide ions to form PbS precipitate. The XPS analysis also proved that a large amount of undissolved PbO and PbS precipitation were adsorbed on the surface of bornite. The adhesion of PbO and PbS on the surface of bornite inhibited dissolution of bornite in the cyanide solution.

Regression models of zinc ion adsorption from aqueous solutions on zeolite from Kholinski deposit, modified with with a sulphur-containing polymer

This article presents regression analysis results of experimental data obtained from a study of the sorption of zinc ions from standardised aqueous solutions using zeolite (clinoptilolite type, Kholinski deposit) modified with a sulphur-containing polymer. Differences in the IR spectra of the modified zeolite were registered before and after sorption of Zn 2+ from an aqueous solution. The effect of the following technological parameters on the adsorption capacity of the modified zeolite was studied: pH, initial concentration of Zn ions in solution, temperature and sorption time of the studied zinc ion extraction. It was shown that the adsorption activity of the modified zeolite of the Kholinsky deposit cannot be approximated by the classical Freundlich and Langmuir equations, since the Zn (II) ion sorption mechanism is complexly coordinated. It was found that the Freundlich equation describes only 40% of the experimental data on the adsorption of zinc ions by a modified zeolite, while the Langmuir equation describes 71%. Accordingly, regression analysis was used to process the measurement results. The found nonlinear regression models reliably describe the observed patterns of sorption and desorption. Kinetic curves of the solution at different temperature conditions are described by exponential models. Adsorption activity toward zinc ions of activated carbon-, as well as natural- and modified-zeolite sorbents was studied. The comparison revealed significant advantages on the part of the modified zeolite: modification of the zeolite surface with a sulphur-containing polymer made it possible to increase its sorption ability by 4.5 times compared to natural zeolite and 9 times compared to activated carbon.

Comparison of the behavior of ZVI/carbon composites from both commercial origin and from spent Li-ion batteries and mill scale for the removal of ibuprofen in water

Zero valent iron/carbon composites were successfully synthesized from commercial iron oxide and graphite (ZVI/C) and also by using graphite obtained from spent Li-ion batteries and iron oxide from mill scale (ZVI/C-X) as a new approach for the valorization of these waste. The composites were synthesized through carbothermic reactions and tested as catalysts for the degradation of ibuprofen from water by Fenton reaction. The optimal conditions for synthesizing ZVI/C composites were a temperature of 1000 °C maintained for 2 h. The structural, and textural features of ZVI/C with different ZVI mass ratios were characterized by different techniques. ZVI/C composites with higher ZVI mass ratios showed higher degradation rates for the removal of ibuprofen both in presence and absence of H2O2. Moreover, ZVI/C-X composite, obtained from industrial waste, showed activity even after four consecutive cycles of use with very low concentration of iron ions in solution after reaction (4.8 mg L−1 after 4 h), which supports the high stability and low Fe-lixiviation of ZVI/C-X composite. The results of this study prove the possibility of synthesizing composites using graphite from spent Li-ion batteries and iron oxide from mill scale, and their potential for the degradation of ibuprofen in water, with comparable activities to those obtained from commercial feedstocks.

XRF analysis of heavy metals contents in oak wood (Quercur robur L.)

XRF analysis of heavy metals contents in oak wood (Quercur robur L.). The aim of this study was to determine an amount of adsorbed metals ions from water solutions by oak ( Quercus robur L.) shavings. This paper focuses on XRF analysis of metal contents in examined samples. Necessary material was obtained from damaged flooring strips. Samples were soaked with standard water solutions of lead (II) nitrate, cadmium nitrate and mercury (II) chloride. After 7 days wood shavings were dried and reduced to ashes in muffle furnace. Content of adsorbed metal was marked (XRF) and classified depending on percentage concentration of metal ions in solutions.

Fast electrodeposition of zinc onto single zinc nanoparticles

The zinc deposition reaction onto metallic zinc has been investigated at the single particle level through the electrode-particle collision method in neutral solutions, and in respect of its dependence on the applied potential and the ionic strength of a sulphate-containing solution. Depending on the concentration of sulphate ions in solution, different amounts of metallic zinc were deposited on the single Zn nanoparticles. Specifically, insights into the electron transfer kinetics at the single particles were obtained, indicating an electrically early reactant-like transition state, which is consistent with the rate-determining partial de-hydration/de-complexation process. Such information on the reaction kinetics at the nanoscale is of vital importance for the development of more efficient and long-lasting nanostructured Zn-based negative electrodes for Zn-ion battery applications.

Wheat Straws and Corn Straws as Adsorbents for the Removal of Cr(VI) and Cr(III) from Aqueous Solution: Kinetics, Isotherm, and Mechanism.

In this paper, the adsorption properties of wheat straw (WS) and corn straw (CS) for Cr(VI) and Cr(III) in solution were studied. The effects of adsorption time, pH of the solution, temperature, and initial concentration of metal ions on adsorption capacity were investigated. The adsorption mechanism was discussed. The results showed that the adsorption isotherms of WS and CS for Cr(VI) and Cr(III) satisfied the Langmuir equation. By fitting the Langmuir equation, the saturated adsorption capacity of WS for Cr(VI) and Cr(III) can reach 125.6 and 68.9 mg g–1, and that of CS for Cr(VI) and Cr(III) can reach 87.4 and 62.3 mg g–1 , respectively. The adsorption kinetics conformed to the pseudo-second-order kinetic equation. The effect of temperature on the adsorption capacity was not significant. Physical diffusion and chemical adsorption coexist in the process of adsorption of metal ions by straws, and chemical adsorption is dominant, and the effect of physical diffusion on the chemical adsorption rate can be neglected. It can be seen from the experimental results that the treatment of chromium-containing wastewater by using cheap and easily available wheat straw and corn straw had a remarkable effect. The adsorbed straw could be completely desorbed and had excellent recyclability, indicating that the straws are ideal adsorbents.

Control of growth solution on the dimensions of gold nanorods accounted for LSPR sensitivity toward liquid ammonia sensing

In the present study, the effect of dimensions of gold nanorods on its sensing property to detect liquid ammonia was reported. Gold nanorods with two different aspect ratios (GNR1 and GNR2) derived from different lengths and diameters were synthesized using seed-mediated growth method, and the aspect ratio was controlled by changing the silver ion concentration in growth solution. The morphological and size measurement was performed using Transmission Electron Microscopy (TEM), and the average value of aspect ratio (AR) was found to be 3.0 and 3.2 for GNR1 and GNR2, respectively. The characteristics transverse and longitudinal mode of localized surface plasmon resonance (LSPR) have been clearly depicted in UV–vis absorption spectrum of both GNR1 and GNR2. The red shift in longitudinal mode of LSPR from 718 to 732 nm has been observed for GNR with change in aspect ratio from 3.0 to 3.2, respectively. These samples of GNR were tested for liquid ammonia sensing with concentration ranging from 100 to 500 ppm. A clear cut blue shift in longitudinal mode of LSPR of prepared gold nanorod was observed. However, the GNR2 was found to be more sensitive toward liquid ammonia sensing. The origin of such blue shifting and sensitivity of longitudinal mode of LSPR of gold nanorod was explained on the basis of orientation dependence and Dipolar Exciton Coupling Model of coupled plasmon in assemblies of anisotropic plasmonic nanoparticles. With the help of this model, blue shifting in longitudinal plasmon band was correlated with the enhanced formation of H-aggregation induced by dipolar coupling of GNR clusters followed by hydrogen bonding after successive addition of ammonia solution.

Corrosion fatigue tests in synthetic seawater with constant temperature liquid circulating system

In this study, a constant temperature liquid circulating (CTLC) system was designed and implemented to control the ion concentration, temperature, and pH value of a corrosive solution during the whole process of corrosion fatigue tests. A set of T-welded-joint specimens were manufactured from Q345qD steel and subjected to corrosion fatigue and fatigue tests. The experimental results show that the corrosive environment greatly reduces the fatigue life of the specimens. The mean reduction in the specimen lifetime is up to 47.7%. These tests also prove that the CTLC system designed in this study and described herein is both reliable and applicable.

PH Switchable Electrochemical and Optical Properties of Polyoctylthiophene – Pyrene Composites

AbstractPolyoctylthiophene electrochemical and optical properties are dependent on the polymer oxidation state, generally requiring presence of doping ions. In this work polyoctylthiophene composites with pyrene or aminopyrene have been prepared and studied using optical and electrochemical methods. It is shown that in the composite formed pyrene molecules act as molecular dopant for the conducting polymer, resulting in a system of partially oxidized polythiophene backbone, yet of high lipophilicity. On the other hand, composite of aminopyrene with polyoctylthiophene is characterized with pH dependent electrochemical and optical properties. The difference arises mostly from the protonation/ deprotonation reaction occurring for aminopyrene embedded in polyoctylothiophene. Nanoparticles of polythiophene‐aminopyrene show turn‐on emission dependence on increase of hydrogen ions concentration in solution in a wide pH range from 12 to 5. For low pH high emission activity is observed for nanoparticles, whereas for films high lipophilicity and low electrochemical activity pointing to presence of semiconducting polymer in the system for protonated aminopyrene. For high pH, when deprotonation of aminopyrene is observed, the system is characterized with low optical, yet high electrochemical activity and low lipophilicity. The electrochemical activity of polyoctylthiophene‐aminopyrene composite can be reversibly switched simply by solution pH change.

Removal of Cd(II) and Pb(II) from aqueous solution by modified attapulgite clay

Three low-cost adsorbents (purified raw attapulgite (A-ATP), high-temperature-calcined attapulgite (T-ATP), and hydrothermal loading of MgO (MgO-ATP)) were prepared as adsorbents for the removal of Cd(II) and Pb(II). By evaluating the effect of the initial solution pH, contact time, initial solution concentration, temperature and coexistence of metal ions on Cd(II) and Pb(II) adsorption, the experimental results showed that MgO-ATP was successfully prepared by hydrothermal reaction and calcination as well as appearing to be a promising excellent adsorbent. At an initial pH of 5.0, A-ATP, T-ATP and MgO-ATP reached maximum adsorption amounts of 43.5, 53.9 and 127.6 mg/g for Pb(II) and 10.9, 11.2, and 25.3 mg/g for Cd(II) at 298 K, respectively. The Cd(II) adsorption on A-ATP was fitted by the Freundlich model, while the adsorption of Pb(II) and Cd(II) on T-ATP and MgO-ATP as well as Pb(II) adsorption on A-ATP agreed with the Langmuir model. All kinetic experimental data favored pseudo second-order model. The calculated thermodynamic parameters suggested that Pb(II) adsorption onto MgO-ATP was spontaneous and exothermic. When considering foreign metal ions, the three adsorbents all presented preferential adsorption for Pb (II). Chemical adsorption had a high contribution to the removal of Cd(II) and Pb(II) by modified attapulgite. In summary, the adsorption was greatly enhanced by the hydrothermal loading of MgO. It aimed to provide insights into the MgO-ATP, which could be able to efficiently remove Cd(II) and Pb(II) and serve as an economic and promising adsorbent for heavy metal-contaminated environmental remediation.

Simulating Continuous Counter-Current Leaching Process for Indirect Mineral Carbonation Under Microwave Irradiation

Mineral carbonation is a promising avenue to realize a deep reduction in carbon dioxide emissions. Though many methods were studied to improve the leaching ratio of mineral leached by ammonium salt, little attention has been received to the problem that the calcium leaching ratio increases while its concentration drops rapidly with the liquid-solid ratio increasing. The continuous counter-current leaching for mineral carbonation process under microwave irradiation is proposed in this study, and the results show that the simulating continuous counter-current leaching process in this article not only is beneficial to improve the leaching ratio and concentration of calcium ions in solution at the same time, but also increases the relative purity of calcium in leached solution. And the produced calcium carbonate products meet the requirements of industrial precipitation of calcium carbonate.

The mechanisms of conventional pollutants adsorption by modified granular steel slag

This study was performed to investigate the removal of phosphorus, nitrogen, ammonia and dissolved organic matter (DOM) from domestic wastewater using modified granular steel slag (GSS) as adsorbent. The modification methods include acid modification, alkalinity modification and thermal modification. The GSS modified at 800°C for 1 h was easier to hydrolyze Ca<sup>2+</sup>, which could promote the precipitation of phosphates and the ion exchange process of ammonia. Therefore, the adsorptive capacity of GSS for phosphates and ammonia could be significantly improved by the thermal treatment. The acid-modified GSS promoted the adsorption capacity of nitrates by increasing surface protonation, specific surface area and pore size. The highest nitrates adsorption capacity was obtained when GSS was immersed in 1 mol/L HCl solution for 24 h. The presence of nitrates inhibited the adsorption of phosphates by GSS because the adsorption of nitrates and phosphates by GSS depended largely on electrostatic attraction and intermolecular force, and the competition between them reduced the adsorption capacity. Ammonia can promote the hydrolysis of metal ions on the surface of GSS, increase the concentration of metal ions in solution and promote the formation of phosphate precipitation, but ammonia also competed with phosphate for active sites on the surface of GSS. The effect of ammonia nitrogen on phosphate adsorption was the result of the interaction of the two mechanisms. For domestic wastewater, the thermally modified GSS showed the best adsorption rate of total phosphorus and total nitrogen, and the acid-modified GSS had better adsorption capacity for organic matter. The thermally modified GSS had a good application effect in laboratory subsurface flow constructed wetlands.

A review of acellular immersion tests on bioactive glasses––influence of medium on ion release and apatite formation

AbstractWhen evaluating new bioactive glass compositions for their suitability as a biomaterial, one of the first steps is the study of their behavior in contact with aqueous solutions. Ion release, pH changes, and apatite precipitation are investigated during immersion experiments, and a wide variety of solutions is used, including simulated body fluid, Tris buffer solution, various cell culture medium formulations or deionized water. This paper reviews the different parameters used for immersion experiments on bioactive glasses. Results show that, depending on solution composition, pH, and buffering capacity, the experimental outcome is likely to vary. In addition, bioactive glass particle size and solution volume/glass surface area ratio affect the resulting ion concentration in solution, and, thus, the rate at which apatite is formed. It is, therefore, important to consider these effects when planning experiments, interpreting results or comparing the results of experiments performed in different laboratories.

Role of Solid-State Miscibility during Anion Exchange in Cesium Lead Halide Nanocrystals Probed by Single-Particle Fluorescence.

In this Letter, we used fluorescence microscopy to image the reversible transformation of individual CsPbCl3 nanocrystals to CsPbBr3, which enables us to quantify heterogeneity in reactivity among hundreds of nanocrystals prepared within the same batch. We observed a wide distribution of waiting times for individual nanocrystals to react as has been seen previously for cation exchange and ion intercalation. However, a significant difference for this reaction is that the switching times for changes in fluorescence intensity are dependent on the concentration of substitutional halide ions in solution (i.e., Br- or Cl-). On the basis of the high solid-state miscibility between CsPbCl3 and CsPbBr3, we develop a model in which the activation energy for anion exchange depends on the density of exchanged ions in the nanocrystal. The heterogeneity in reaction kinetics observed among individual nanocrystals limits the compositional uniformity that can be achieved in luminescent CsPbCl3-xBrx nanocrystals prepared by anion exchange.

Kinetics simulation of transmembrane transport of ions and molecules through a semipermeable membrane.

We have developed a model to study the kinetics of the redistribution of ions and molecules through a semipermeable membrane in complex mixtures of substances penetrating and nonpenetrating through a membrane. It takes into account the degree of dissociation of these substances, their initial concentrations in solutions separated by a membrane, and volumes of these solutions. The model is based on the assumption that only uncharged particles (molecules or ion pairs) diffuse through a membrane (and not ions as in the Donnan model). The developed model makes it possible to calculate the temporal dependencies of concentrations for all processing ions and molecules at system transition from the initial state to equilibrium. Under equilibrium conditions, the ratio of ion concentrations in solutions separated by a membrane obeys the Donnan distribution. The Donnan effect is the result of three factors: equality of equilibrium concentrations of penetrating molecules on each side of a membrane, dissociation of molecules into ions, and Le Chatelier's principle. It is shown that the Donnan distribution (irregularity of ion distribution) and accordingly absolute value of the Donnan membrane potential increases if: (i) the nonpenetrating salt concentration (in one of the solutions) and its dissociation constant increases, (ii) the total penetrating salt concentration and its dissociation constant decreases, and (iii) the volumes ratio increases (between solutions with and without a nonpenetrating substance). It is shown also that only a slight difference between the degrees of dissociation of two substances can be used for their membrane separation.

Optimization of process using carboxymethyl chitosan for the removal of mixed heavy metals from aqueous streams

This paper highlights the efficacy of carboxymethyl chitosan (CMCh), a bio-degradable water-soluble derivative of chitosan for the separation of a mixture of heavy metal ions such as copper, nickel, zinc and lead from aqueous streams, as they constitute, the major industrial pollutants present in wastewater. The experimental studies are conducted using commercially available ultrafiltration module using synthetic solutions of the contaminants. The design of experiments was performed by Response Surface Methodology (RSM) with split-plot D-optimal design. Parametric studies were carried out using initial pH of the feed solution, loading ratio (P/M) and initial metal ion concentration to assess the percentage rejection and recovery of metal ions. The maximum percentage rejection of Cu(II), Ni(II), Zn(II) and Pb(II) with CMCh were found to be 100%, 100%, 95%, and 98% respectively under optimum conditions. Subsequently the metal ions were recovered collectively by reversing the pH to 2. The results show that CMCh could be an effective size enhancing species for the removal and recovery of mixture of metals by SEUF.

Using Cilantro (Coriandrum Sativum) to Remove Cadmium from Contaminated Water

Accessibility to safe drinking water poses great risks to human health since heavy metal ions can accumulate their amounts along the food chain. Methods already in use for cleaning contaminated water have resulted in generating toxic sludge and are expensive. Cilantro leaves has been used to reduce the contamination of heavy metals like lead, mercury and copper in rod shellfish as contains bioactive components of flavonoids, saponines and fibers which are capable of absorbing heavy metal ions by chelating action. However, the most effective part of cilantro and the most effective form i.e. when green or dry has not been reported. Consequently, the present study aimed at investigating adsorption of Cd2+ ions by fresh and dry cilantro leaves and stems from simulated water. Cilantro fresh leaves and fresh stems were grounded to obtain the wet adsorbents while for the dry adsorbents, fresh cilantro leaves and stems were sun dried at room temperature until their weighed dry masses remained constant and grounded to fine powder. Batch sorption studies were carried out while varying parameters of contact time, shaking speed, temperature, adsorbent dose, pH and initial concentration of metal ions in solution. Residue Cd2+ ions concentrations were determined using atomic adsorption spectroscopy (AAS). The adsorption of Cd2+ ions was described by Langmuir isotherm with Qmax values of 250.00, 51.28, 4.68 and 15.06 mg/g for fresh leaves (FL), fresh stems (FS), dry leaves (DL) and dry stems (DS) biomasses respectively. The results from this study suggest that fresh and dry cilantro leaves and stems are potential adsorbents of Cd2+ ions.

Theory of Multicomponent Phenomena in Cation-Exchange Membranes: Part II. Transport Model and Validation

Multicomponent mass-transport in cation-exchange membranes involves the movement of multiple species whose motion is coupled one to another. This phenomenon mediates the performance of numerous electrochemical and water purification technologies. This work presents and validates against experiment a mathematical model for multicomponent mass transport in phase-separated cation-exchange membranes (e.g., perfluorinated sulfonic-acid ionomers). Stefan-Maxwell-Onsager theory describes concentrated-solution transport. Hydrodynamic theory provides constitutive relations for the solute/solvent, solute/membrane, and solvent/membrane friction coefficients. Classical porous-medium theories scale membrane tortuosity. Electrostatic relaxation creates friction between ions. The model uses calculated ion and solvent partitioning between the external solution and the membrane from Part I of this series and incorporates the corresponding ion speciation into the transport coefficients. The proposed transport model compares favorably to properties (e.g., membrane conductivity, transference numbers, electroosmosis, and permeability) measured in dilute and concentrated aqueous binary and ternary electrolytes. The results reveal that the concentration and type of ions in the external solution alter the solvent volume fraction and viscosity in the hydrophilic pathways of the membrane, changing macroscale ionomer conductivity, permeability, and transference numbers. This work provides a physicochemical framework to predict ion-exchange-membrane performance in multicomponent systems exhibiting coupled transport.

Высшие грибы как сорбенты ионов кадмия

It is known that fungal chitin exhibits high sorption properties with respect to heavy metal ions, while it is practically not absorbed in the human body, which makes it a promising sorbent. The aim of this work was to evaluate the sorption abilities of the mushrooms of Agaricus bisporus and Russula atropurpurea with respect to cadmium ions. The use of the potentiometric method for measuring the potential of the ion-selective electrode, which depends on the concentration of cadmium ions in solution, made it possible to register in detail in real time the kinetic curves of sorption of cadmium ions by mushrooms. During the experiment, it was found that the kinetics of sorption of cadmium ions from a solution with initial concentrations (0.2-2.0)·10-5 M by the preparations of fruit bodies of mushrooms A. bisporus and R. atropurpurea is well described by the pseudo-second order equation, according to which the limiting stage of the process is chemical interaction of sorbent and sorbate (1:1 ratio). At relatively low initial concentrations of cadmium ions in solution ((0.2-0.6)·10–5 M), the sorption rate was 1.5-2.5 times higher for R. atropurpurea compared to A. bisporus. At higher concentrations of cadmium ions in solution ((0.8-2.0)·10-5 M) the speed and capacity of sorption were very close for different types of mushrooms. Moreover, the rate of sorption by mushrooms exceeds 5-10 times the rate of sorption of activated carbon and micromycetes of the genus Fusarium. It was revealed that the sorption isotherm of cadmium ions by mushrooms is well described by the Dubinin-Radushkevich equation, according to which R. atropurpurea is characterized by the highest sorption compared to A. bisporus. Thus, R. atropurpurea has the highest sorption activity with respect to cadmium ions.