Effect of peroxide depolymerization of chitosan on properties of chitosan sulfate particles produced from this substance

Effect of the oxidative destruction of chitosan on the rate at which a dispersed phase is formed in its dilute solutions in the presence of sulfate ions and on the composition, size and ζ-potential of submicrometer chitosan sulfate particles being formed was studied. It was found that the particle size steadily decreases as the molecular mass of chitosan becomes smaller, and the sedimentation stability of aqueous dispersions increases in the absence of surfactants. The \(\nu _{SO_4 } :\nu _{NH_2 }\) molar ratio in chitosan sulfate particles is independent of the molecular mass of chitosan and varies within the range 0.45–0.46. A pH-dependence of the sign of the ζ-potential with isoelectric point at pH 5.0 was found for particles based on destructed chitosan.     

Electrokinetic properties of aluminum oxide nanodispersions in NaCl solutions

Using a Zetasizer Nano analyzer, electrophoretic mobility and particle sizes are studied as depending on the pH (3–11) and concentration (10^?3–10^?1 M) of NaCl background solutions for two samples of aluminum oxide, namely, γ-oxide of the Degussa brand and a sample synthesized by aluminum chloride hydrolysis. The values of the electrokinetic ζ potential are calculated through the Smoluchowski equation and with allowance for the effect of the polarization of electrical double layer on the electrophoretic mobility within the framework of the Overbeek-Boes-Wiersema model (ζ_W). It is established that, in the region of the isoelectric point (IEP), at (pH-pH_IEP) = ±1.5, the |ζ_W|-pH dependences are linear and their slopes are almost equal for both aluminum oxide samples. The difference between the positions of IEPs for γ-oxide and synthesized oxide sample may be related to different degrees of their surface hydration.     

Effect of polyelectrolytes and polyelectrolyte mixtures on the electrokinetic potential of dispersed particles. 2. Electrokinetic potential of silica particles in electrolyte, polyelectrolyte and polyelectrolyte mixtures solutions

The effect pH, ionic strength (KCl concentration), weakly and medium charged anionic and cationic polyelectrolytes (PEs) as well as their binary mixtures on the electrokinetic potential of silica particles as a function of the polyelectrolyte/mixture dose, its composition, charge density (CD) of the PE, and way of adding the polymers to the suspension has been studied. It has been shown that addition of increasing amount of anionic PEs increases the absolute value of the negative zeta-potential of particles at pH > pH isoelectric point (IEP = 2.5); this increase is stronger the charge density of the polyelectrolyte is higher. Adsorption of cationic polyelectrolytes at these pH values gives a significant decrease in the negative ζ-potential and overcharging the particles; changes in the ζ-potential are more pronounced for PE samples with higher CD. In mixtures of cationic and anionic PE at pH > pHIEP, the ζ-potential of particles is determined by the adsorbed amount of the anionic polymer independently of the CD of PEs, the mixture composition and the sequence of addition of the mixture components. Unexpectedly, the ζ-potential of silica at pH = 2.1, i.e. < pHIEP, turned out to be positive in the presence of both anionic PE and cationic + anionic PE mixtures. This is explained by formation (and adsorption onto positively charged silica surface) of pseudo-cationic PEs from anionic ones due to transfer of protons from the solution to the amino-group of the anionic polymer. Considerations about the role of coulombic and non-coulombic forces in the mechanism of PE adsorption are presented.     

Formation of silver nanoparticles in aqueous carboxymethyl cellulose solutions and the evolution of their sizes

Size dependences of silver nanoparticles synthesized in aqueous carboxymethyl cellulose solutions and dependences of their ζ-potentials on solution pH are studied by the dynamic light scattering method. Variations in nanoparticle size distributions and ζ-potential of particles with time are monitored. It is revealed that the size of silver nanoparticles decreases linearly with an increase in solution pH. The size of particles noticeably decreases in the aging process of the colloidal solution. The ζ-potential tends to one and the same value with time for all studied hydrosol samples.     

Mutual effect of the interaction of human serum albumin with cellulose in water

Adsorption of human serum albumin to microcrystalline cellulose interface has been determined as functions of protein concentration and pH of the aqueous solutions. The maximum adsorption value is reached at the protein isoelectric point. The study of adsorption at several values of pH indicates that its interaction with the MCC interface is not controlled by the electrostatic effect. The FTIR, ¹³C NMR data reveal that human serum albumin denaturates at its IEP and its macromolecules become extended. Resulting intercalates consist of microcrystalline cellulose, albumin, and solvent.     

The effects of some electrolytes on flocculation with a cationic polyacrylamide

The effects of sodium chloride, sodium sulfate, and alum (aluminum sulfate) on the performance of a cationic polyacrylamide flocculant in a papermaking suspension consisting of bleached (hardwood: softwood, 50∶50) kraft wood-pulp fibres and anatase (TiO₂) were investigated. Sodium chloride and sodium sulfate, 1×10^?5 to 1×10^?2 M, in the presence of polymer, caused negligible changes in the electrophoretic mobility of the TiO₂ and in the first-pass retention of TiO₂ (heteroflocculation of TiO₂ and fibres). Alum at concentrations from 1×10^?5 to 1×10^?4 M at pH 4.0 and 4.5 increased retention with polymer; higher alum concentrations resulted in lower retentions. At pH 4.0 the electrophoretic mobility of the TiO₂ was positive over the entire range of alum concentrations investigated (1×10^?5?3.2×10^?3 M) whereas at pH 4.5 the mobility was negative at 1×10^?5 M alum and charge reversal was observed at about 4×10^?5 M alum. The intrinsic viscosity of the cationic polyacrylamide was decreased by the addition of alum, sodium chloride or sodium sulfate. The effect of alum on the polymer conformation appeared to be that of the non-specific interaction of sulfate ions with a cationic polyelectrolyte. Retention results are discussed in terms of the colloidal stability of TiO₂, the adsorption of polyacrylamide on TiO₂ and the conformation of adsorbed polymer.     

Solvent Extraction of Vanadium with α-Benzoin Oxime

The solvent extraction of vanadium by a chloroform solution of α-benzoin oxime was investigated. The most favorable condition for the extraction has been found in the pH rang of 1.8 to 3.0 in sulfate or chloride buffer solutions, but with better extraction efficiency when sulfate was used. A solution of 2×10^?2 M α-benzoin oxime in chloroform was used, and 1×10^?4 to 2×10^?2 M vanadium(V) was extracted favorably in about 89% yield by a single extraction, and in about 97% yield by a double extraction. The effects of shaking time, concentration of α-benzoin oxime, and diverse ions have also been investigated. Vanadium(V) can be readily extracted without interference in the presence of copper(II), aluminum(III), iron(III), silver(I), zirconium(IV), and chromium(III).     

Application of Tetra Cyclohexyl Tin(IV) as an Anionic Carrier for the Construction of a New Salicylate Membrane Sensor

A new tin complex namely tetracyclohexyl tin(IV) (TCHT) was synthesized and used as the ion carrier for the construction of a highly selective salicylate sensor. This sensor shows a Nernstian response to salicylate ions over a very wide concentration (1.0 × 10^?7–1.0 × 10^?1 M) in a pH range of 5.5–10.5. The optimum selectivity and response could be obtained for a membrane incorporating 30% PVC, 61% BA, 3% of cationic additive (HTAB) and 6% of TCHT. The response time of the electrode is very short in the whole concentration range (15 s). The electrode also shows an excellent discriminating ability for salicylate ions with respect to the most common organic and inorganic anions including chloride, sulfate, nitrate, nitrite, cyanide, sulfite, iodide, thiocyanate, phosphate, acetate, oxalate, citrate, and tartarate ions. The detection limit of the proposed sensor is 8.0 × 10^?8 M. The electrode was successfully used for determining the concentration of salicylate ion in synthetic serums.     

Formation of the dispersed phase in mixed solutions of chitosan and magnesium sulfate

Specific features of formation and the composition and characteristics of dispersed phase particles in mixed dilute solutions of chitosan and magnesium sulfate, containing no surfactants, were studied. The component molar ratio, \(\nu _{SO_4 } :\nu _{NH_2 }\) , is the factor exerting the strongest influence on the formation rate and characteristics of chitosan sulfate particles. With an increase in the fraction of sulfate ions in the initial solution, the particle size decreases and their ζ-potential increases. The \(\nu _{SO_4 } :\nu _{NH_2 }\) molar ratio in chitosan sulfate particles only slightly depends on the composition of the initial mixed solution and varies within 0.40–0.44.     

Entwicklung einer flieβinjectionsmethode zur bestimmung von chlorid im spurenbereich durch leitfähighkeitsdiffernzenA flow-injection method for the determination of trace amounts of chloride

The indirect determination of chloride in water is based on measurement of the difference in conductivity after the sample has passed through ion-exchange columns in the hydrogen form and silver form. The linear response range is about 0.5–10 μg g^?1 chloride (with 3 μg g^?1 nitrate and 5 μg g^?1 sulfate); the detection limit is about 50 ng g^?1 chloride but depends strongly on the concentrations of other anions.     

Synthesis of manganese oxide sols by KMnO<Subscript>4</Subscript> reduction with polyvinyl alcohol in an aqueous medium

Manganese oxide sols were synthesized using the chemical condensation method by KMnO₄ reduction with polyvinyl alcohol in an aqueous medium. The resulting gels were characterized by the manganese oxide content of 0.07–0.19 wt %, pH 9.5–10.2, and ζ-potential of–(20.3–42.9) mV. Spectrophotometric, turbidimetric, and dynamic light scattering methods were employed to determine how the particle size, ζ-potential, pH, and manganese oxide content in the resulting sols were affected by the KMnO₄ concentration and the KMnO₄ : polyvinyl alcohol ratio. The most stable sols preserved stability for over180 days and remained stable up to 0.5 M KCl, CaCl₂, and AlCl₃ concentrations.     

Aggregation and sedimentation stability of microcrystalline cellulose suspensions in aqueous aluminum nitrate solutions

The aggregation and sedimentation stability of dilute suspensions of microcrystalline cellulose in aqueous solutions of Al(NO₃)₃(2 × 10⁻⁵–2 × 10⁻³ mol/l) is studied by the photometric method at pH 2–11. It is found that, in the absence of Al(NO₃)₃, microcrystalline cellulose suspensions are stable with respect to aggregation throughout the pH range in question. The addition of Al(NO₃)₃ induces the coagulation and accelerates the sedimentation of microcrystalline cellulose aggregates. At all concentrations of Al(NO₃)₃, the maximum loss in stability is observed at pH 7–9. Original Russian Text ? P.M. Mosur, A.V. Lorentsson, Yu.M. Chernoberezhskii, 2009, published in Kolloidnyi Zhurnal, 2009, Vol. 71, No. 4, pp. 566–568.     

La matrice eau de mer et le signal du cuivre en spectrometrie d'adsorption atomique sans flamme : Partie 1: Etude de l'influence des principaux composants

(Copper signals from seawater matrices in electrothermal atomic absorption spectrometry. Part 1: study of the effects of principal inorganic ions.)The effects of the main inorganic ions of seawater (Na⁺, Mg²⁺, Ca²⁺, Cl^?, SO^2?₄), and of nitrate as modifier, on the electrothermal atomic absorption spectrometric signal of copper are studied. Sodium chloride, sulfate or nitrate, magnesium chloride or nitrate, and calcium chloride can cause serious interferences. Thermal treatment at about 700°C prevents the interference of MgCl₂ by its hydrolysis. Ashing can be done without loss of copper at higher temperatures in the presence of sulfate salts (1300°C) and nitrate salts (1200°C) than in the presence of chloride salts (1100°C). This is ascribed to the stabilising effect of oxides and sulfides. A study of the influence of two-component matrices, MCl-MNO₃ or MCl-MSO₄, on the atomization signal of copper confirms this stabilizing effect which adds to the decrease in interference connected with removal of chloride in acidic medium.     

A coated-platinum sulfate-selective electrode

Sulfate-selective electrodes can be fabricated from commercial platinum electrodes by coating them with a mixture of Aliquat-336 and trifluoroacetyl-p-butylbenzene in polyvinyl chloride matrix. Adding a solid, sparingly soluble sulfate such as that of strontium, lead, barium, or 2-aminoperimidine (2-AP) improves the selectivity for sulfate relative to nitrate. The 2-AP electrode shows the best physical stability and is described in detail. The order ofanion interference is ClO₄^->Cl^->NO₃^->H₂PO₄^->F^-. The useful pH range is 4–9. The response is Nernstian from 10^-5 to 10^-1 M in sodium sulfate solutions.     

Determination of traces of inorganic anions by means of high-performance liquid chromatography on zipaxsax columns

Zipax-SAX pellicular beads are used as the anion-exchanger material ; a high-pressure packing technique is described. A Zipax-SAX column (200 × 4.5 mm) is used in a separation system with eluent suppression and conductivity detection as in ion-chromatography. Good separation of chloride, nitrite, bromide, nitrate and sulfate is obtained with 1.4 × 10^-3 M succinate or adipate eluents at pH 7. A complete separation takes about 6 min at a flow rate of 3 ml min^-1. Detection limits of 2 μg l^-1 chloride, 4 μg l^-1 nitrate and 10 μg l^-1 sulfate can be reached if 2 ml of sample is preconcentrated.     

Applications of ion-exchange minicolumns in a flow-injection system for the spectrophotometric determination of anions

Displacement of thiocyanate from a strongly basic ion-exchange resin by other anions is used to determine common anions at the 10^?5–10^?4 M level by spectrophotometric detection of the iron(III)/thiocyanate complex. Chloride and sulphate can be removed by incorporating a pre-column containing a cation-exchange resin in the silver form followed by a zinc reductor, thus allowing the determination of nitrate in their presence. Binary mixtures (e.g., chloride and nitrate) can be determined simultaneously by splitting the sample in the flow system so that part goes through the chloride suppressor (giving a nitrate response only) and part by-passes it giving a response to both chloride and nitrate.     

Environmentally abundant anions influence the nucleation, growth, Ostwald ripening, and aggregation of hydrous Fe(III) oxides

The simultaneous homogeneous and heterogeneous precipitation of hydrous Fe(III) oxides was investigated in the presence of environmentally ubiquitous anions (nitrate, chloride, and sulfate). Experiments were conducted with 10(-4) M Fe(III) at acidic pH (pH = 3.7 ± 0.2), which often occurs at acid mine drainage sites or geologic CO(2) storage aquifers near injection wells. Quartz was used as a model substrate for heterogeneous precipitation. Small angle X-ray scattering (SAXS) and grazing incidence SAXS (GISAXS), atomic force microscopy (AFM), and dynamic light scattering (DLS) measurements were conducted. In situ SAXS/GISAXS quantified the size, total particle volume, number, and surface area evolutions of the primary nanoparticles formed in the nitrate and chloride systems. In both systems, the heterogeneously precipitated particles were smaller than the homogeneously precipitated particles. Compared with chloride, the volume of heterogeneously precipitated hydrous Fe(III) oxides on the quartz surface was 10 times more in the nitrate system. After initial fast heterogeneous nucleation in both nitrate and chloride systems, nucleation, growth, and aggregation occurred in the nitrate system, whereas Ostwald ripening was the dominant heterogeneous precipitation process in the chloride system. In the sulfate system, fast growth of the heterogeneously precipitated particles and fast aggregation of the homogeneously precipitated particles led to the formation of particles larger than the detection limit of GISAXS/SAXS. Thus, the sizes of the particles precipitated on quartz surface and in solution were analyzed with AFM and DLS, respectively. This study provides unique qualitative and quantitative information about the location (on quartz surfaces vs in solutions), size, volume, and number evolutions of the newly formed hydrous iron oxide particles in the presence of quartz substrate and ubiquitous anions, which can help in understanding the fate and transport of pollutants in the environment.     

Highly Selective and Sensitive Triiodide PVC‐Membrane Electrode Based on a New Charge‐Transfer Complex of Bis(2,4‐Dimethoxybenzaldehyde)butane‐2,3‐Dihydrazone with Iodine

In this work, a highly selective membrane triiodide sensor based on a new charge‐transfer complex of bis(2,4‐dimethoxybenzaldehyde)butane‐2,3‐dihydrazone with iodine (Iodide Charge Transfer complex: ICT) as membrane carrier is introduced. The influences of five different solvent mediators on sensitivity and selectivity of the proposed sensor were considered. The best performance was obtained with the membrane composition containing 30% poly (vinyl chloride), 63% DBP, 5% ICT and 2% HTAB. The electrode shows a Nernstian behavior over a very wide triiodide ion concentration range (1.0 × 10^?7‐1.0 × 10^?2 M), and a detection limit value of 8.0 × 10^?8 M. The effect of pH on the potentiometric response of the sensor was also studied, and it was found that the response of the electrode is independent of the pH of the solution in the pH range of 4.0–10. The proposed sensor has a very fast response time (< 12 s), and good selectivities relative to a wide variety of common inorganic and organic anions, including iodide, acetate, bromide, chloride, fluoride, nitrite, nitrate, sulfite, sulfate, cyanide and thiocyanate. In fact the selectivity behavior of the proposed triiodide ion‐selective electrode shows great improvements compared to the previously reported electrodes for triiodide ion. The proposed membrane sensor can be used for at least 6 months without any divergence in the potentials. The electrode was successfully applied as an indicator electrode in the titration of triiodide with thiosulfate ion.     

Study of Cadmium Extraction with Aliquat 336 from Highly Saline Solutions

A large number of model solutions with high ionic strength were synthesised to mimic industrial conditions and were used as a first approach to study Cd extraction in the presence of chloride at high salinity, as experienced in real industrial solutions. The extractant used throughout in this work was Aliquat 336, a quaternary ammonium salt well known to the hydrometallurgical industry. The effects of some selected anions in addition to chloride (i.e., perchlorate, nitrate, and sulfate) were studied. The distribution of cadmium was measured using ¹⁰⁹Cd as a tracer. Liquid-scintillation spectroscopy quantified the concentration of ¹⁰⁹Cd in both phases. Raman and NMR spectroscopy were employed to gain further insight into the extraction chemistry. A careful analysis of all Cd extraction data showed that within specific windows of the reactant concentrations the chemical reactions could be represented by simplified equations, as discussed thoroughly in the text. Equilibrium constants for the extraction of \({\text{CdCl}}_{3}^{ - }\) from chloride and chloride/sulfate media were determined to be log₁₀K_ext?=?4.9?±?0.8 and log₁₀K_ext?=?5.7?±?0.5, respectively. For the nitrate environment, an exchange reaction involving a LiNO₃ ion pair is proposed and agrees with the experimental data, but was not proven. ¹⁴N-NMR and Raman spectroscopy confirmed that the relative affinity of Aliquat 336 for the relevant anions followed the order: perchlorate?>?nitrate?>?chloride?>?sulfate. Finally, ¹⁴N-NMR enabled the equilibrium constant of the exchange reaction between nitrate and chloride for Aliquat 336 to be determined.     

Study of the Heterocoagulation Process in Aqueous System with Three-Component Dispersed Phase Microcrystalline Cellulose‒TiO<Subscript>2</Subscript>‒TiOSO<Subscript>4</Subscript>

Coagulating effect of titanyl sulfate on a mixed aqueous dispersion of microcrystalline cellulose and TiO₂ was examined. The particle retention on a filter and the filtration rate of the microcrystalline cellulose?TiO₂?TiOSO₄ ternary system were evaluated in a wide range of pH values.