Transport Studies of Monovalent Ions through Nafion-117 Ion Exchange Membrane in Presence of Polyacrylate

The results of equilibrium distribution and transport kinetics of monovalent (Li⁺, Na⁺, and Cs⁺) ions through Nafion-117 ion exchange membrane in presence of polyacrylate anion have been presented. For Na⁺-Li⁺ system, equilibrium distributions in the presence and absence of polyacrylate have been found to be the same indicating that the Donnan membrane equilibrium is not affected by the presence of polyacrylate. For the Na⁺-Cs⁺ system, a favored transport of Cs⁺ ion to the polyacrylate compartment has been observed, indicating the binding of Cs⁺ ion with polyacrylate is stronger than other monovalent ions. This is due to the lower hydration radius of Cs⁺ ions. The deviation from Donnan membrane equilibrium condition has been used to obtain information about the fraction of counter-ions bound to the polyacrylate. The transport profile in the presence of polyacrylate has also been calculated based on the modified Nernst Planck (NP) approach, taking into account the fraction of counter-ions bound to the polyacrylate ion. The Donnan relation has been used to obtain the concentration of ions at the solution/membrane interface. The self-diffusion coefficients of ions and membrane ion exchange capacity have been given as input parameters in the calculations. The calculated time profile has been found to agree well with the experimental time profile.     

Absence of Donnan Exclusion at High‐Concentration Ion Exchange for Macroporous Anionic Resin

Abstract

High‐concentration ion exchange has been studied for an anionic macroporous resin. The mechanism of interaction of Lewatit MP‐500 (strong base resin) with several high‐concentration inorganic salts was analyzed in order to determine the effect of the Donnan potential in the process.

The systems under study were Cl^?, SO₄ ^2? as counter‐ions and K⁺, Na⁺ as co‐ions in different combinations as single electrolytes. These salts were chosen because of their interest as raw materials in the fertilizer industry. The study focuses mainly on the behavior of high‐concentration (over 1 M) counter‐ and co‐ions in the anionic resin. The results showed that Donnan exclusion does not take place completely and that electrolyte penetration inside the resin is observed. Furthermore, a certain amount of ion exchange was observed for the co‐ions (K⁺ and Na⁺) when the resin was presaturated with sulphate and chlorides that were present in the solution. Equilibrium and kinetics data were obtained under these special experimental conditions. Equilibrium constants were obtained for counter‐ions and adsorption constants for co‐ions using a constant separation factor isotherm, while diffusion coefficients were obtained using a pore diffusion model.     

Metal ion removal by dyed cellulosic materials

Further studies on adsorption of different metal ions by the four dyed and undyed cellulosic substrates namely cotton fibers, bleached bamboo pulp, jute fibers, and sawdust were carried out. Different metal ions adsorbed were Fe²⁺, Fe³⁺, Pb²⁺, and Hg²⁺. The equilibrium metal adsorption was studied by EDTA method. The control and dyed substrates adsorbed these metal ions to a significant extent, thus providing an effective and cheap method for adsorption of costly but polluting and toxic metals like Pb²⁺ and Hg²⁺. The adsorption levels varied up to 95% for various substrate–dye–metal ion combinations.     

THERMODYNAMICS OF ALKALI AND ALKALINE EARTH METAL ION - EXCHANGE ON CERIUM(IV) HYDROGEN PHOSPHATE

ABSTRACT

Thermodynamics of alkali and alkaline earth metal ions/hydrogen ions exchange on a fibrous cerium(IV) hydrogen phosphate have been investigated. Selectivities for alkali and alkaline earth metal ions increase in the order; Na⁺<<K⁺<Rb⁺<Cs⁺ and Mg²⁺<Ca²⁺<Sr²⁺<Ba²⁺, respectively. The enthalpy changes for alkali metal and Ba2+ ions/H⁺ exchange are negative, those for the other alkaline earth metal ions/H⁺ exchange are positive, indicating that the enthalpy changes for monovalent ions are more favorable than those for divalent ions. In comparison with ions of the same valency, the enthalpy change decreases with the atomic number of the metal ion corresponding to a decrease in the entropy change of dehydration in response to enthalpy-entropy compensation.     

Sorption of simple ions by nylon 6

The sorption isotherms of Na⁺ and Cl^? ions by nylon 6 from aqueous soluations at pH = 2.2, 4.0, and 6.0 are reported. Detailed analysis of the results showed that they could not be interpreted satisfactory by the classical Gilbert-Rideal or Donnan equilibrium treatments usually applied to nylon and/or wool. On a qualitative basis, the former model may be considered more successful, but, even so, the behavior of the partition coefficient of Na⁺ cannot be explained. This difficulty persists even when some important restrictions imposed by the simple Donnan equilibrium treatment are relaxed, as in the models of Glueckauf and of McGregor and Harris. A different theoretical viewpoint is put forward here, which explains the observed behavior qualitatively and shows how it fits into the general pattern of ion sorption by polyelectrolytes in general and by amphoteric polyelectrolytes in particular. The conclusions drawn also have important implications concerning previous interpretations of ion sorption by wool.     

Infrared Absorption Spectra of Cellulose Pulps of Palm Tree

Palm leaves are used for the production of different cellulose pulps; their properties are investigated, the resulting pulps were bleached by a multistage process, the effects of the addition of solvent during the pulping process on the chemical structure of the pulps are discussed. The strength properties of the paper which is produced from unbleached and bleached pulps increased with increasing cellulose percentage and decreasing lignin content in the pulp. Infrared absorption spectra were recorded for different unbleached and bleached pulp in the frequency range 200–4000 cm^-1 by using the alkali halide disk technique; the factors which affect the experimental technique were calibrated through these studies. The structural units within pulping yield (holocellulose, hemicellulose, cellulose, lignin, and ash) were interpreted within the pulp network structure by the infrared absorption spectra, where different samples of unbleached, bleached soda, and kraft pulps were also elucidated by IR spectra, after preheating at different temperatures and with using different ratios of organic solvents. The addition of organic solvents decreased or increased the crystallinity indices, depending on the type of solvent and the pulping temperature. It was also found that, at the same pulping temperature (155°C) and with the same percent of organic solvents in the pulping liquor, the asymmetry indices also the mean hydrogen bonding strength (A _OH/A_CH) of the unbleached soda pulps (organosolv or nonorganosolv pulping) were less than that of unbleached kraft pulps, except for the pulps obtained by pulping with dioxan at 155°C. The mean hydrogen bond strength of the bleached pulps decreased or increased, depending on the type solvent used and the pulping temperature.     

Lichen Substances Affect Metal Adsorption in <Emphasis Type="Italic">Hypogymnia physodes</Emphasis>

Lichen substances are known to function as chelators of cations. We tested the hypothesis that lichen substances can control the uptake of toxic metals by adsorbing metal ions at cation exchange sites on cell walls. If true, this hypothesis would help to provide a mechanistic explanation for results of a recent study showing increased production of physodalic acid by thalli of the lichen Hypogymnia physodes transplanted to sites with heavy metal pollution. We treated cellulose filters known to mimic the cation exchange abilities of lichen thalli with four lichen substances produced by H. physodes (physodic acid, physodalic acid, protocetraric acid, and atranorin). Treated filters were exposed to solutions containing seven cations (Ca²⁺, Cu²⁺, Fe²⁺, Fe³⁺, Mg²⁺, Mn²⁺, and Na⁺), and changes to the solution concentrations were measured. Physodalic acid was most effective at influencing metal adsorption, as it increased the adsorption of Fe³⁺, but reduced the adsorption of Cu²⁺, Mn²⁺, and Na⁺, and to a lesser extent, that of Ca²⁺ and Mg²⁺. Reduced Na⁺ adsorption matches with the known tolerance of this species to NaCl. The results may indicate a possible general role of lichen substances in metal homeostasis and pollution tolerance.     

Metal Ion‐Catalyzed Hydrothermal Liquefaction of Calcium Lignosulfonate in Subcritical Water

Three metal ion catalysts, namely, Na⁺, K⁺, and Ca²⁺, were tested to improve liquefaction of calcium lignosulfonate, and their effects on product distribution were specifically investigated. Results showed that metal ion catalysts favored the production of hydrogen as well as of phenolic compounds. The total contents of phenolic compounds catalyzed by metal ions were generally higher than 75 %. The catalysis abilities of Na⁺ and K⁺ were better than that of Ca²⁺. The neutral‐alkaline condition was much more beneficial to calcium lignosulfonate liquefaction. Compared to the hydrochars with Na⁺ and K⁺ catalysts, the hydrochars with Ca²⁺ catalyst had higher carbon content and a higher heating value.     

Size and Shape of Montmorillonite Particles Saturated with Na/Ca Ions (Inferred from Viscosity and Optical Measurements)

The viscosity and light transmittance of montmorillonite suspensions saturated with Na⁺, Ca⁺⁺ and known mixtures of these ions in the adsorbed phase were investigated. Introduction of a small fraction of Na⁺ (10% – 15%) into the exchange complex of Ca—clay, does not result in the breakdown of the tactoids. The breakdown of the tactoids occurred when the equivalent fraction of Na increased from 0.2 to 0.5. Montmorillonite clay saturated with 50% calcium (and less) exists as single platelets. Combining the structural data with an equilibrium equation based on the diffuse double layer theory indicates that when tactoids are formed, demixing occurred by which Na⁺ ions are concentrated on the external surfaces of the tactoids and Ca⁺⁺ ions on the internal surfaces.     

ION EXCHANGE SELECTIVITY OF A RESORCINOL-FQRMALDEHYDE POLYCONDENSATE RESIN FOR CESIUM IN RELATION TO OTHER ALKALI METAL IONS

ABSTRACT

Ion exchange isotherms for the ion-pairs Li⁺ -Cs⁺, Na⁺ -Cs⁺ and K⁺ -Cs⁺ have been measured for a cesium selective resorcinol—formaldehyde polycondensate resin synthesized in the laboratory- The equilibrium data have been used to calculate the thermodynami c equilibrium constants as well as standard free energies of ion ex change and thus arrive at a selectivity series for the above ions- The high selectivity towards cesium as compared to other alkali metal ions has been discussed in the 1ight of existing theories and models of ion ex change phenomena.     

Influence of K+ and Na+ ions on the degradation of wet‐spun alginate fibers for tissue engineering

A synthetic type of wet‐spun alginate fibers were immersed in simulated body fluid(SBF) composed of K⁺, Na⁺, and Ca²⁺ cations with various concentrations. Experimental measurements revealed that Na⁺ had a greater impact on degradability than that of K⁺ ion. The finding was further confirmed by the characterization of mass loss, ICP, XRD, and theoretical analyses. The degradation process and mechanism were demonstrated through the research on swelling behavior and mass loss. Besides, the wet‐spun alginate fibers were characterized by FT‐IR, XRD, and SEM. The results showed that the degradation mechanism could be attributed to the ion‐exchange between Ca²⁺ of the synthetic alginate fibers and Na⁺, K⁺ of the solutions under the osmotic pressure. The synthetic fibers were swelled and then degraded faster with the presence of Na⁺ ion presented greater influence on degradability compared with K⁺ ion. The degradation results of a mechanical rupture of fibers due to excessive water uptake without the occurrence of any chemical changes in the spun alginates structure. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44396.     

Influence of pulp bleaching and compatibilizer selection on performance of pulp fiber reinforced PLA biocomposites

This article focuses on the effect of pulp bleaching and emerging commercial compatibilizers on physical performance of pulp fiber reinforced poly(lactic acid) (PLA) biocomposites. Industrially bleached and unbleached hardwood kraft pulp fibers are treated with several additive types, and compounded with PLA to fiber content of 30 wt %. After injection molding, the produced biocomposites are evaluated by their mechanical performance and fiber–matrix adhesion. For selected materials, fiber surface and fiber properties are reflected to composite performance by analyzing the compositions, dimensions, and lignin coverage of original fibers, as well as fiber dispersion and dimensions after melt processing. As a conclusion, unbleached kraft pulp fibers provide significant improvement in physical properties of PLA/pulp fiber composites. Of the screened compatibilizers, epoxidated linseed oil has a clear positive effect on performance when bleached kraft pulp fibers are used. The improvements correspond to enhanced fiber–matrix adhesion and differences in remaining fiber length distributions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47955.     

Predicting the dynamics and performance of a polymer–clay based composite in a fixed bed system for the removal of lead (II) ion

A polymer–clay based composite adsorbent was prepared from locally obtained kaolinite clay and polyvinyl alcohol. The composite adsorbent was used to remove lead (II) ions from aqueous solution in a fixed bed mode. The increase in bed height and initial metal ion concentration increased the adsorption capacity of lead (II) and the volume of aqueous solution treated at 50% breakthrough. However, the adsorption capacity was reduced by almost 16.5% with the simultaneous presence of Ca²⁺/Pb²⁺ and Na⁺/Pb²⁺ in the aqueous solution. Regeneration of the adsorbent with 0.1 M of HCl also reduced its adsorption capacity to 75.1%. Adsorption of lead (II) ions onto the polymer–clay composite adsorbent in the presence of Na⁺ and Ca²⁺ electrolyte increased the rate of mass transfer, probably due to competition between cationic species in solution for adsorption sites. Regeneration further increased the rate of mass transfer as a result of reduced adsorption sites after the regeneration process. The length of the mass transfer zone was found to increase with increasing bed height but did not change with increasing the initial metal ion concentration. The models of Yoon–Nelson, Thomas, and Clark were found to give good fit to adsorption data. On the other hand, Bohart–Adams model was found to be a poor predictor for the column operation. The polymer–clay composite adsorbent has a good potential for the removal of lead (II) ions from highly polluted aqueous solutions.     

Ion Exchange in Selected Low Rank Coals. Part I: Equilibrium

ABSTRACT

The ion exchange behavior of 4 low rank coals has been investigated. Their total carboxyl group contents ranged from 1.52 meq/g for a subbituminous coal to 2.78 meq/g for a lignite. The coverage of the carboxyl groups by metal cations varied from 30% to 60% (on an equivalent basis) for the raw coals. For all raw coals, Ca²⁺was the predominant metal cation. The equilibrium ion exchange behavior of metal cations for H⁺was found to be a linear function of pH regardless of the cation concentration in solution. Thus, the extent of exchange is a function of available hydrogen ions. From equilibrium ion exchange measurements, the following cation exchange selectivity pattern for a subbituminous coal was determined:

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while that for a lignite was:

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ION EXCHANGE PROPERTIES OF THE SODIUM PHLOGOPITE AND BIOTITE

ABSTRACT

The ion exchange behavior of three sodium micas (phlogopite, Ward's Sci.; phlogopite, Suzorite Inc., biotite, Ward's Sci.) towards Li⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺. Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺ Hg²⁺, Co²⁺, Cu²⁺ Cd²⁺ and Zn²⁺ ions has been studied. The ion exchange isotherms of alkali, alkaline earth and some other divalent cations were determined and concentration equilibrium constants as a function of metal loading and temperature were analyzed. Sodium micas exhibit high affinity for heavy alkali metals with the selectivity order Rb⁺ > Cs⁺ > K⁺. By studying the cesium uptake in the presence of NaNO₃, CaCl₂, NaOH, NaOH+KOH, HNO₃ electrolytes (in the range of 0.01–6 M) it was found that sodium micas could remove cesium efficiently in neutral and alkaline media, which make them promising for certain types of nuclear waste treatment.     

Clinoptilolites for nitrogen/methane separation

Clinoptilolites, naturally occurring zeolites, currently used by nuclear industry for ion exchange and drying, were evaluated for the nitrogen/methane separation. Ion exchange of purified clinoptilolite was carried out individually with the cations Na⁺, Mg²⁺, Ca²⁺, K⁺ and H⁺, and the adsorption isotherms and diffusion rates were measured. Purified and Mg-clinoptilolite show potential for nitrogen/methane separation and high-pressure adsorption isotherms were measured in a differential absorption bed. Pressure swing adsorption simulations were performed for purified clinoptilolite, Mg-clinoptilolite and the commercial sorbent ETS-4. Purified clinoptilolite shows slightly higher recovery and lower productivity than ETS-4 for similar product purity (∼95%). Mixed ion-exchanged clinoptilolites of Mg/Ca cations, K/Na cations and Mg/Na cations were also prepared and studied for the nitrogen/methane separation. Mg/Na (50/50) mixed ion-exchanged clinoptilolite exhibits very good equilibrium and kinetic selectivity in the low-pressure range, better than purified clinoptilolite. Mixed-exchange clinoptilolites were also found to show a wide range of adsorption characteristics with varying ratios of cation exchange, thereby making them suitable for further improvements in nitrogen/methane separation.     

Inward Migration of Glass‐Modifier Cations During Heat Treatment Under an N2 Atmosphere

An Na⁺/Ca²⁺‐deficient layer is observed to form on the glass surface region up to a depth of hundreds of nanometers when a soda‐lime‐silicate glass is heat treated under an N₂ atmosphere near its glass‐transition temperature. The measurements were performed using X‐ray photoelectron spectroscopy with C₆₀‐ion sputtering (C₆₀‐XPS) and dynamic secondary‐ion mass spectrometry (D‐SIMS) with consideration of the mass and charge balances. The increase in the amount of hydrogen is substantially less than the decrease in the total charge due to the loss of modifier cations in the Na⁺/Ca²⁺‐deficient layer; furthermore, the oxygen concentration in this layer is lower than the bulk value, suggesting that the silanol groups in the surface layer of the glass are dehydrated. A high‐concentration layer of Ca²⁺ is also confirmed in the dehydration layer of the glass heat treated under an N₂ atmosphere, suggesting that Na⁺ and Ca²⁺ ions migrate inward into the glass via an ion‐exchange reaction with protons, which migrate toward the surface from the bulk. We also confirmed that a thicker Na⁺/Ca²⁺‐deficient layer is formed on glass surfaces with higher water content. Our results suggest that the dehydration of the silanol groups is the driving force of the inward migration of Na⁺ and Ca²⁺ ions.     

Adsorption of β-carotene: II. On cation exchanged bleaching clays

X-ray diffraction patterns of a number of commercial bleaching earths indicate that they consist mainly of montmorillonite mixed with smaller amount of kaolinites as well as mica, quartz and cristobalite. The active sites in these earths for the adsorption of β-carotene are identified through ion exchange and found to be the protonic sites and some metallic ions. The efficiencies of the various cations in imparting activities to the earths are found to be in the order Mg²⁺ > Fe³⁺ > H⁺ > Ca²⁺ > Na⁺. For Fe³⁺ and H⁺ exchanged clays, the activity was found to be linear function of the concentration of these ions. The high activities of Mg²⁺ and Ca²⁺ exchanged clays are discussed. Presented in part as paper T12 in the International Conference on Palm Oil Product Technologies in the Eighties, Kuala Lumpur, May 1981.     

Application of jojoba wax bound to polyethylene membranes and hollow fibers in ion‐exchange and pervaporation processes

Chlorosulfonated polyethylene membranes and hollow fibers were reacted with allylic amino jojoba to bind the wax chemically to the polymer. The modified membranes and hollow fibers were then tested in the ion‐exchange and pervaporation processes, respectively. The jojoba‐bound polyethylene membranes were selective in preventing transfer of divalent ions such as Ca²⁺ and Mg²⁺, while monovalent ion such as K⁺ and Na⁺ could penetrate the membranes. The flux of the monovalent ions depended on the amount of jojoba bound to the polymer, which acted as a barrier to the ions (the monovalent ions could be eluted by acid washing). The concentration of ions (in the range of 0.05–1.0 N) in the feed solution had little effect on the flux. Preliminary results of pervaporation of a dioxane/water mixture through hollow fibers made of jojoba‐bound chlorosulfonated polyethylene show separation of the dioxane from the water with a separation factor of 6. This technique can be applied to remove residual organic solvents in the purification of industrial waste water. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 763–768, 2001     

Characterization of Adsorptive Capacity and Investigation of Mechanism of Cu2+, Ni2+ and Zn2+ Adsorption on Mango Peel Waste from Constituted Metal Solution and Genuine Electroplating Effluent

Abstract

The present study reports the potential of mango peel waste (MPW) as an adsorbent material to remove Cu²⁺, Ni²⁺, and Zn²⁺ from constituted metal solutions and genuine electroplating industry wastewater. Heavy metal ions were noted to be efficiently removed from the constituted solution with the selectivity order of Cu²⁺ > Ni²⁺ > Zn²⁺. The adsorption process was pH-dependent, while the maximum adsorption was observed to occur at pH 5 to 6. Adsorption was fast as the equilibrium was established within 60 min. Maximum adsorption of the heavy metal ions at equilibrium was 46.09, 39.75, and 28.21 mg g for Cu²⁺, Ni²⁺, and Zn²⁺, respectively. Adsorption data of all the three metals fit well the Langmuir adsorption isotherm model with 0.99 regression coefficient. Release of alkali and alkaline earth metal cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) and protons H⁺ from MPW, during the uptake of Cu²⁺, Ni²⁺, and Zn²⁺, and EDX analysis of MPW, before and after the metal sorption process, revealed that ion exchange was the main mechanism of sorption. FTIR analysis showed that carboxyl and hydroxyl functional groups were involved in the sorption of Cu²⁺, Ni²⁺, and Zn²⁺. MPW was also shown to be highly effective in removing metal ions from the genuine electroplating industry effluent samples as it removed all the three metal ions to the permissible levels of discharge legislated by environment protection agencies. This study indicates that MPW has the potential to effectively remove metal ions from industrial effluents.