Characteristics and fouling propensity of polysaccharides in the presence of different monovalent ions

In this study the fouling behavior of alginate in the presence of monovalent ions (i.e., NaCl, KCl, CsCl, NaBr, and NaI) was explored. Results showed that alginate tended to be less negatively charged in the presence of monovalent ions. The cation ion identity had a more substantial impact on the zeta potentials of alginate solution than the anion ion identity, which was likely due to preferential attraction between alginate and cation ion. Nevertheless, significantly increased particle size was observed for alginate in 150 mM CsCl, possibly arising from the specific interaction between alginate and Cs⁺. Membrane fouling was more severe for alginate in monovalent solutions, particularly at 150 mM ionic strength. The unified membrane fouling index was increased by cation and anion ions in the order of Na⁺ > K⁺ > Cs⁺ and Cl^? > Br^? > I^?, respectively. Nevertheless, the addition of monovalent ions could promote the fouling reversibility. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2501–2507, 2016     

COMPARISON OF ION EXCHANGE AND DONNAN EQUILIBRIUM MODELS FOR THE PH-DEPENDENT ADSORPTION OF SODIUM AND CALCIUM IONS ONTO KRAFT WOOD PULP FIBERS

ABSTRACT

Management of nonprocess element (NPE) accumulation in pulp washing operations requires equilibrium models that predict the distribution of metals between the wash liquor and the pulp fibers. The overall goal of this study was to assess models for predicting the multi-component adsorption of hydrogen ions (H⁺), sodium ions (Na⁺), and calcium ions (Ca⁺²) onto bleached and unbleached kraft pulp fibers over a pH range of 2.7–11. As part of this study, binary equilibrium constants for hydrogen and metal ion exchange on carboxylate sites in bleached pulp (0.041 meq/g dry pulp) were measured at 25°C, with log K ^Na/Ca = ?1.604 ± 0.119, log K ^H/Ca = 0.633 ± 0.087, and intrinsic dissociation constant pK _io of 3.64 ± 0.46. Ion exchange and Donnan equilibrium models adequately predicted the multi-component equilibrium data for competitive adsorption of H⁺, Na⁺, and Ca⁺² onto bleached kraft wood pulp fibers. The ion exchange model was fully predictive, whereas the Donnan model required that the solution pH be known. At pH 2.7–6, the Donnan model predicted the adsorption of Na⁺ and Ca⁺² onto both bleached and unbleached wood pulp fibers better than the ion exchange model. The ion exchange model assumed that residual carboxylate in the pulp served as the only site for the competitive binding of hydrogen and metal ions. In contrast, the Donnan model assumed a non site-specific distribution of metal ions between charged fiber and external solution phases and a carboxylate site specific adsorption of hydrogen ions. Above pH 6, both models failed to predict that the calcium adsorption on unbleached brownstock pulp increased beyond the carboxylate site capacity, suggesting that other functional groups within the brownstock pulp with intrinsic dissociation constant values higher than carboxylate were providing additional binding sites for calcium.     

Microbial interactions with caesium—implications for biotechnology

The continuing release of caesium isotopes into the environment has highlighted the necessity for efficient removal of Cs from industrial waste effluents prior to discharge. Existing technologies, e.g. zeolite ion-exchange for Cs removal, can be expensive and microbial metal adsorption/accumulation may represent a cheap alternative. The distinct chemical properties of Cs⁺, which dictate a high degree of metabolism-dependent uptake via monovalent cation transport systems, indicate that different approaches are required for biological Cs removal to those which are generally adopted for other metals/radionuclides. The low toxicity of Cs⁺ eliminates one potential problem in the use of live cells for Cs removal. High levels of Cs⁺ accumulation have been reported in a number of microorganisms, but uptake levels vary markedly in different organisms and are strongly influenced by a number of physico-chemical and mechanical parameters, e.g. the use of batch or continuous-flow systems, biomass immobilization (which tends to increase Cs⁺ adsorption at the expense of metabolism-dependent accumulation), pH and particularly the prevalence of other monovalent cations such as K⁺ and Na⁺. Inherent differences in Cs⁺ uptake capacities of different microorganisms appear to be largely attributable to differences in the affinity of monovalent cation transport systems for Cs⁺. The application of rigorous screening procedures involving the use of autoradiography has great potential for isolation of microorganisms with particularly high affinities for Cs⁺. Alternatively, manipulation of the physiological status of microorganisms can dramatically alter the transport of Cs⁺ and other monovalent cations. Hyper- and hypo-osmotic shock, respectively, have so far proved to be the most successful treatments for stimulating Cs removal and recovery. Other manipulations, at both the cellular and molecular level, which are known to influence K⁺ fluxes but have yet to be characterized for Cs⁺, are outlined here.     

Studies on the use of chromium ferrocyanide gels in the treatment of radioactive wastes

The sorption and distribution of some radioisotopes on chromium ferrocyanide gels under different physical conditions has been investigated. The exchanger shows high selectivity for Tl⁺, Cs⁺, Cd²⁺ and Pb²⁺. A complete elution of Cs⁺, Tl⁺ and Rb⁺ is possible with suitable eluants whereas Pb²⁺ and Cd²⁺ cannot be desorbed. The uptake of monovalent ions is by an ion exchange process unlike the sorption of bivalent ions.     

THERMODYNAMICS OF ALKALI AND ALKALINE EARTH METAL ION-EXCHANGE ON ZIRCONIUM SULPHOPHOSPHONATES

The thermodynamics of alkali and alkaline earth metal ion exchange on a layered zirconium sulphophosphonate having the general composition Zr(O₃PC₆H₄SO₃H) _×(HPO₄) _2?× yH₂O have been investigated. Enthalpy and entropy changes accompanying the M²⁺ - H⁺ exchange (M = Na⁺, Cs⁺, Mg²⁺ and Ba²⁺)were determined by the temperature variation method. For the monovalent ions, Na⁺ and Cs⁺, the enthalpy terms favor exchange whereas the entropy terms are unfavorable. In contrast, for the divalent ions, Mg²⁺ and Ba²⁺, the exchange is due to highly favorable entropy terms.     

Isotopic ion-exchange studies in heteroionic systems

Isotopic ion-exchange studies were carried out for Mn²⁺ ions in the presence of Ba²⁺, Sr²⁺ Cs⁺ and Na⁺ ions, and for Na⁺ ions in the presence Ba²⁺ and Mn²⁺ ions, from 0.1 N chloride solutions. Single Particle Radioactive Tracer technique was employed, and the exchanger Dowex 5OW-X8 was used. The Nernst-Planck model, taking into account the diffusion processes both in the film and in the resin bead, was employed to analyse the data Resin-phase self-diffusion coefficients obtained from the isotopic exchanges in the homo-ionic systems, and liquid-phase diffusion coefficients calculated from limiting ionic conductance data, were used. The computer results agreed well with the experimental data for the following cases: (i), Na⁺ exchange in the presence of Ba²⁺ and Mn²⁺ ions; (ii), Mn²⁺ ion in the presence of Na+ ions; and (iii), Mn²⁺ exchange in the presence of Ba²⁺, Sr²⁺ and Cs⁺ ions at higher fractions of Mn²⁺ ions. However, lower values of diffusion coefficient of Mn²⁺ ions could correlate the data with smaller fractions of Mn²⁺ ions. It has been shown ibat resinphase diffusion mechanism of homovalent ions under similar environments is similar.     

Donnan Dialysis with Ion-Exchange Membranes. II. Diffusion Coefficients Using Same Valence Ions

Abstract

Donnan dialysis with ion-exchange membranes was investigated experimentally. The equation derived theoretically in the previous paper was fitted to the results of a Donnan dialytic experiment, and the diffusion coefficients of various kinds of ions and in various kinds of ion-exchange membranes were obtained. The flux of monovalent ions in Donnan dialysis was much larger than that of bivalent ions. Thus, monovalent drive ions are the best kind of drive ions to employ. It was found that the ratio of the diffusion coefficient in the ion-exchange membrane to that in the solution remained constant at 70 for monovalent feed and drive ions except for H⁺ ions, and at 175 for bivalent feed and drive ions. It became apparent that the fundamental equation derived from Fick's equation and no electric current might be used for Donnan dialysis instead of the Nernst-Planck equation.     

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.     

Rapid and phase pure synthesis of microporous copper silicate (CuSH–1Na) with 12-ring channel system

Phase pure sample of the microporous copper silicate CuSH–1Na has been obtained by simplified hydrothermal method without using additives (H₂O₂ and Na₂HPO₄). Ion exchange of Na⁺ by Cs⁺, Ca²⁺ and Sr²⁺ ions showed that the structure can suffer partial replacement of the charge compensating cations. Ion exchange with Cs⁺ resulted in distinct dehydration while the ion exchange with Sr²⁺ increased the total amount of water. Water content in the Ca-exchanged sample is comparable to the as-synthesized sodium phase. Raman spectroscopy revealed that the divalent cations as Ca²⁺ and Sr²⁺ induce stronger local structural deformations than the monovalent Cs⁺. These structural changes have been also followed by the refined lattice distortions. Magnetic analyses showed that CuSH–1Na presents a very weak ferromagnetic interaction along the Cu²⁺ chains with a nearly vanishing Curie–Weiss temperature. This magnetic coupling is associated with super-super-exchange interactions through Cu–Na–O–Na–Cu paths. Antiferromagnetic coupling, attributed to inter-chains super-super-exchange interactions, competes with the ferromagnetic one and prevails at the lowest temperature.     

Diffusion and Selective Transport of Alkali Cations on Cation-Exchange Membrane

Abstract

The diffusion coefficients and selective transport for alkali metal cations through a charged polysulfonated ICE-450 ion-exchange membrane were measured as a function of pH at 25°C. The permeability and diffusion coefficients were found to increase in the sequence Cs⁺ ≥ K⁺ > Na⁺ > Li⁺. The relationship between the permeability and the diffusion coefficients, and the hydrated radii of cations in the membrane were shown. This sequence was also explained by considering the hydration of ions in the membrane. The selectivity transport of K—Na and K—Li binary systems at various pH gradients through the membrane were also investigated under various conditions. In the selective transport of metal ions, the selectivity depended on both the hydrated ionic size and the interaction between the fixed groups in the membrane and the metal ions.     

Structures,properties, and alkali metal ion transport membrane of polyelectrolyte complexes consisting of methyl glycol chitosan,glycol chitosan,and poly(vinyl sulfate)

Mixtures of methyl glycol chitosan and glycol chitosan were reacted with poly(vinyl sulfate) to form many different water-insoluble polyelectrolyte complexes (PEC) in aqueous solution at various hydrogen ion concentrations. It was revealed from elemental analyses, infrared (IR) spectroscopy, and solubilities of PEC that molecular structures of each PEC are dependent on [H⁺]. PEC membranes were made from casting solutions of all kinds of PEC, and transport phenomena through the membrane of PEC prepared in a pH 13.0 solution were investigated under various conditions. The transport ratio of Na⁺ and the electric potential difference between the left- and right-hand sides of the membrane were measured, and it is suggested that the driving force for active transport depends on the membrane potential, Donnan potential and diffusion potential. Moreover, permeability of K⁺ was higher than that of Na⁺ in selective transport.     

Kinetics of ring opening of propylene sulphide: 1. Alkali metal and cryptated alkali metal carbazyl salts

The reactivities of free ions and ion pairs have been determined for the ring opening of propylene sulphide with carbazyl salts, in THF at ?30°C. A large increase of the ion pair reactivity is observed on increasing the size of the counterion (Na⁺ < Cs⁺ < Na⁺ + |222|). Moreover, cryptated carbazyl ion pairs are three times more reactive than free ions in the same manner as thiolate species for the propagation of propylene sulphide in similar conditions.     

+ alumina—A novel Li+ solid electrolyte

Li⁺ is one of several monovalent cations known to completely replace Na⁺ in Na⁺ beta alumina. The exchange occurs readily to approximately 50% producing a physically stable Li⁺ solid electrolyte having a conductivity of approximately 10^?3 (Ωcm)^?1 at 25°C. The Li⁺ transport number through Li⁺-Ni⁺ beta alumina is nearly 1 for compositions having Li⁺/Na⁺ greater than 1. Li⁺ ions migrate through the solid electrolyte lattice without significantly altering its Na⁺ content. This paper discusses our work examining ionic equilibrium, Li⁺ transport, ionic conductivity, and stability of Li⁺-Na⁺ beta alumina. The extraordinary preferential Na⁺ occupation of the beta alumina structure even in the presence of high Li⁺ activity is discussed and similar behavior predicted for another beta alumina composition.     

Interactions of Some Hofmeister Cations with Sodium Dodecyl Sulfate in Aqueous Solution

In this work, we have investigated the influence of some alkali metal ions on the Krafft temperature (T_K) and critical micelle concentration (CMC) of a classical ionic surfactant, sodium dodecyl sulfate (SDS), over a wide range of temperature. The alkali metal cations such as Li⁺, Na⁺, Cs⁺, and K⁺ are found to affect the solubility and hence the T_K of the surfactant. It was observed that kosmotropic Li⁺ lowers the T_K of the surfactant. Due to the common ion effect, the solubility of SDS decreases in the presence of Na⁺, resulting in an increase in the T_K. On the other hand, chaotropic K⁺ and Cs⁺, capable of forming contact ion pairs with the chaotropic dodecyl sulfate ion, lower the solubility and hence elevate the T_K. In terms of decreasing the T_K, the ions follow the trend: Li⁺ > Na⁺ > Cs⁺ > K⁺ except for 0.0025 M CsCl. The added cations screen the charge of the micelle surface and facilitate closer packing of the surfactant with a consequent decrease in the CMC. In terms of the effectiveness in lowering the CMC, the ions follow the order: Cs⁺ > K⁺ > Na⁺ > Li⁺. In the presence of added electrolytes, the γ_CMC values are found to be lower than the corresponding values in pure water. The thermodynamic parameters (Gibbs free energy, enthalpy, and entropy changes) of micellization were calculated to gain insights into the mechanism of the process.     

Liquid Membrane Separations of Metal Cations Using Macrocyclic Carriers

Abstract

The selectivity in water and methanol solvents of macrocyclic crown ether ligands toward univalent and bivalent cations is well known. Incorporation of these ligands into chloroform liquid membranes separating water and salt solution phases results in a system showing selective cation transport. The cation transport rates of single cations across these liquid membranes have been correlated with equilibrium constant values for cation-macrocycle interaction in methanol. This correlation has been extended to binary cation mixtures of Cs⁺ with Li⁺, Na⁺, K⁺, and Rb⁺. A model for cation transport from these cation mixtures has been reduced to an equation which gives good agreement between measured and predicted transport rates across our liquid membranes.     

Selective Transport of Alkali and Alkaline Earth Metallic Ions through a Supported Liquid Membrane Containing Tripentyl Phosphate as a Carrier

Abstract

A selective transport system for alkali and alkaline earth metallic ions with a perchlorate ion as a pairing ion species through a supported liquid membrane (SLM) containing tripentyl phosphate (TPP) as a carrier is described. The SLM used is a porous polypropylene membrane impregnated with TPP solution in o-nitrophenyloctylether. The effects of the pairing ion species, the initial perchlorate concentration, and the TPP concentration on metallic ion transportability are examined under various experimental conditions. The permeation velocities of the metallic ions in the transport system followed the sequence Li⁺?Na⁺>K⁺>Mg²⁺; that is, a highly selective transport for Li⁺ ion was observed. Compared with the transport rates of alkali metallic ions, those of transition metallic ions such as Cu²⁺ and Fe³⁺ ions are very low. The permeation velocities of alkali and alkaline earth metallic ions through an SLM are dependent on the concentrations of perchlorate and TPP. Equations for the permeation velocities of Li⁺, Na⁺, K⁺, and Mg²⁺ ions through an SLM, based on two concentrations of perchlorate and TPP, are proposed.     

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.     

Transport of chromium through cation-exchange membranesby Donnan dialysis in the presence of some metals of different valences

The transport of a trivalent chromium ion through charged polysulfonated cation-exchange membranes in the presence of metals of different valences under Donnan dialysis conditions was studied as a function of pH gradient at 25°C. The recovery factor (RF) values of chromium ion were obtained, and it was found that the RIF values decreased with the increasing of the metal valence. The transport of chromium ions through membranes was correlated with the flux data, which depended on the metal valences as well as the structure of the membrane. It was observed that the transport was influenced with H⁺ ion concentration in the receiver phase.     

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.     

Pervaporation separation of water–ethanol mixtures using metal‐ion‐exchanged poly(vinyl alcohol) (PVA)/sulfosuccinic acid (SSA) membranes

Poly(vinyl alcohol)/sulfosuccinic acid (PVA/SSA) membranes in the hydrogen form were converted to monovalent metal ion forms Li⁺, Na⁺, and K⁺. The effect of exchange with metal ions was investigated by measuring the swelling of water–ethanol (10/90) mixtures at 30 °C and by the pervaporative dehydration performance test for aqueous ethanol solutions with various ethanol concentrations at 30, 40, and 50 °C. In addition, electron spectroscopy for chemical analysis (ESCA) analysis was carried out to study the quantity of metal ions in membranes. From the ESCA analysis, the lithium ion quantity in the resulting membranes is greater than that of any other metal ions in question because of the easy diffusion of a smaller metal ion into the membrane matrix. The swelling ratio was in the following order: PVA/SSA‐Li⁺ > PVA/SSA‐Na⁺ > PVA/SSA‐K⁺ membranes. For pervaporation, the PVA/SSA‐Na⁺ membrane showed the lowest flux and highest separation factor for all aqueous ethanol solutions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1867–1873, 2002