UPTAKE OF METAL IONS BY A NEW CHELATING ION-EXCHANGE RESIN. PART 5 : THE EFFECT OF SOLUTION MATRIX ON ACTINIDES

ABSTRACT

The influence of commonly occurring matrix constituents on the uptake of representative actinides in the tri-, tetra-, and hexavalent oxidation states by a new chelating ion exchange resin, called Diphonix?, has been investigated. The effect of increasing concentrations of HF at three fixed HC1 concentrations on the retention of U(VI), Np(IV), and Am(III) was measured. All three actinides showed strong retention in HF even up to a concentration of 1 M The effect of sulfuric, oxalic and phosphoric acids at three fixed HNO₃ concentrations on the retention of Th(IV), U(VI), and Am(III) was also measured. Only when the concentration of the complexing acids was above 0.1 M was the retention of the actinides decreased significantly at 0.1 M HNO₃ The effect was much less pronounced at higher HNO₃ concentrations.

Sodium, calcium, aluminum and iron were selected to study the influence of cationic matrix constituents on the uptake of actinide ions by Diphonix. In the case of tetra- and hexavalent actinides (represented by Th and U, respectively) only the very highest concentrations of Fe(III) and Al(III) caused a significant decrease in the retention of the two higher valent actinides. On the other hand, Am(III) retention was significantly lowered by Al and Fe(III) concentrations above 10^?2 M The influence of Al and Fe(III) on the uptake of Am(III) may be minimized by use of fluoride ion to complex Al and by reducing Fe(III) to Fe(II). Macroconcentrations of sodium and calcium had only minimal influence on the uptake of actinides in all three oxidation states.     

Anion complexation by calix[4]arene-TTF conjugates

Calix[4]arenes bearing tetrathiafulvalene (TTF) moieties appended to the upper rim via the amidic functions were synthesized and used for ¹H NMR and UV/Vis complexation studies towards selected anions. It was found that the complexation affinity towards H₂PO₄⁻ dramatically depends on the substitution pattern of the calixarene moiety. As a result, the proximally disubstituted derivative has a complexation constant by two orders of magnitude higher than the distally disubstituted analogue. The differences between proximal and distal receptors were also documented by their behaviour during the oxidation of the attached TTF units.     

Corrosion Behaviour of Ti–4Al–4V Alloy in Nitric, Phosphoric and Sulfuric acid Solutions at Room Temperature

Electron beam melting of Ti-6-4 scrap has been carried out. Aluminium losses were verified for all the runs and commercial-size ingots of Ti-4-4 alloy were obtained. Tensile tests and hardness measurements have shown that the Ti-4-4 alloy has mechanical strength close to the Ti-6-4 alloy as well as higher ductility. The corrosion behaviour of the Ti-4-4 alloy was investigated in HNO₃, H₃PO₄ and H₂SO₄ solutions at room temperature. Ti-4-4 alloy is passive in all HNO₃ solutions and in 20 wt% H₃PO₄ and presents an active behaviour in 40–80 wt% H₃PO₄ and in all H₂SO₄ solutions. Ti-4-4 alloy is highly corrosion resistant in HNO₃ and 20 wt% H₃PO₄ and has a moderate resistance in 40 wt% H₃PO₄. Ti-4-4 alloy can be regarded as a potential candidate to replace CP–Ti in these media. In more concentrated H₃PO₄ solutions, and in H₂SO₄, very high corrosion rates were observed.     

Use of vivianite (Fe3(PO4)2.8H2O) to prevent iron chlorosis in calcareous soils

For various reasons, iron phosphate might be effective in correcting Fe chlorosis in calcareous soils. To test this hypothesis, several pot experiments were conducted using an Fe chlorosis-sensitive chickpea (Cicer arietinum L.) cultivar cropped in soils to which partially oxidized vivianites (Fe₃(PO₄)₂.8H₂O) and Fe(III) phosphates with different characteristics had been added. Vivianites mixed with the soil at a rate of 1 g kg^–1 were as effective in preventing chlorosis as Fe chelate (FeEDDHA). However, the effectiveness of Fe(III) phosphates was less, suggesting that the presence of Fe(II) in the phosphates used was a key factor in their Fe-supplying value to plants. The effectiveness of vivianites, however, seemed to be largely independent of their Fe(II) content.The future of vivianite as a Fe amendment will depend not only on economic considerations (production and application costs) but also on its long-term capacity to release plant-available Fe in soil environments.     

Immobilized Phosphate Ligands with Enhanced Ionic Affinity through Supported Ligand Synergistic Interaction

Abstract

The ability of a secondary group to influence the metal ion affinities of a primary ligand immobilized on crosslinked polystyrene beads is reported. The secondary groups were glycol units, ‐(CH₂CH₂O)_1‐4‐, and their effect on phosphate ligands was studied. The affinities of Pb(II), Cd(II), Cu(II), Ni(II), Zn(II), Fe(III), Y(III), La(III), Eu(III), Lu(III), and U(VI) were quantified from HNO₃, HCl, and H₂SO₄ solutions in concentrations up to 4 N. Affinities were highest for U(VI) and the trivalent ions. The glycol units enhanced the extent of metal ion complexation by the phosphate ligands through coordination of the metal ion and not through an auxiliary group effect (where there would be a direct interaction between the glycol units and the phosphate ligand) as indicated by the similarity in the FTIR spectra of the four phosphorylated glycol resins. At least two glycol units are needed for synergistic cooperation between the glycol and phosphate in binding metal ions.     

Simulation of Fe-Al compounds developed during single superphosphate manufacture

In order to analyse iron phosphate complexes and gel-like phases encountered in the single superphosphate process, experiments were performed with a free-Al, Fe apatite crystal of Durango from Mexico phosphate rock and sulfuric acid. Reaction products were studied by X-ray diffraction and surface analysis methods namely X-ray photoelectron spectroscopy and scanning electron microscopy. Results show that in a free Al, Fe-system, part of the Ca(H₂PO₄ )₂.H₂O (MCPM) forms before precipitation of any CaSO₄(CS) and gel-like phase such H₂SO₄.yH₃PO₄.xH₂O is formed. When iron is added, the precipitation rate of (CS) and (MCPM) increases and Fe₃(H₃O)H₈(PO₄)₆.6H₂O is formed. When Fe and Al are added, a gel-like phase is quickly formed with a molar ratio that changes with time and develops into crystalline compounds. The composition of this gel may be represented as a mixture of two phases: H₂SO₄.yH₃PO₄.xH₂O and a gel containing Al-Fe-Si.     

The role of polyaniline salts in the removal of direct blue 78 from aqueous solution: A kinetic study

Three polyaniline salts (PANI–H₂SO₄, PANI–H₃PO₄, and PANI–HNO₃) have been synthesized by chemical oxidative polymerization of aniline. They have been tested as adsorbents for the removal of the textile dye direct blue 78 (DB78) from aqueous solution. The interaction followed pseudo-second-order kinetics whether the rate of interaction was measured from the depletion of dye concentration in solution or the increase in the amount of dye adsorbed on the PANI surface. The removal rate was a function of the activity of the polymer as well as the reaction parameters of the polymer/dye system. The activity of the PANI depended on the polymerization conditions. These conditions involve the concentration of aniline, ammonium peroxydisulfate as oxidant, and sodium dodecylsulfate (SDS), the type of dopant acid (H₂SO₄, H₃PO₄, HNO₃), and the polymerization time. Higher removal rate was observed at oxidant/aniline mole ratio equals 1. The rate of removal was in the order PANI–H₃PO₄ > PANI–H₂SO₄ > PANI–HNO₃. The rate decreased with increasing the concentration of DB78 and pH. It increased with increasing the load of PANI. Pseudo-second-order kinetics, external surface adsorption, and intraparticle diffusion models were concurrently operating in the removal of DB78 with PANI.     

Assessment of soil washing for Zn contaminated soils using various washing solutions

Bench-scale soil washing experiments were conducted to remove Zn from contaminated soils. Various washing solutions including hydrochloric acid (HCl), nitric acid (HNO₃), sodium hydroxide (NaOH), oxalic acid (HOOCCOOH·2H₂O), sulfuric acid (H₂SO₄), phosphoric acid (H₃PO₄), and tartaric acid (C₄H₆O₆) were used. The concentration of the washing solutions used in this study ranged from 0.1 M to 2 M with a liquid to solid ratio of 10. The soil washing results showed the following order of washing solution decreasing effectiveness for the removal of Zn: HCl > HNO₃ > H₂SO₄ > H₃PO₄ > C₄H₆O₆ > HOOCCOOH·2H₂O > NaOH.     

Third Phase Formation in the Extraction of Inorganic Acids by TBP in n‐Octane

Abstract

The extraction of HNO₃, HClO₄, H₂SO₄ and H₃PO₄ by 20% (v/v) TBP (0.73 M) in n‐octane was measured under identical conditions up to and beyond the critical point of third phase formation (Limiting Organic Concentration, or LOC condition). The data, together with those obtained previously for HCl, allowed us to establish the following lyotropic series of effectiveness with respect to third phase formation in the extraction of acids by TBP: HClO₄>H₂SO₄>HCl>H₃PO₄>HNO₃. This series correlates with the amount of water present into the organic phase at the point of phase splitting. This result reinforces the validity of the reverse micellar model developed previously for the extraction of metal salts by TBP. The measurements of LOC values as a function of temperature revealed major differences among the acid‐TBP systems investigated. For HClO₄, the strong increase of the LOC value with increasing temperatures is accompanied by a large favorable entropy change. The opposite is true for HCl, while H₂SO₄ and H₃PO₄ represent intermediate cases. Measurements of the LOC values for the extraction of HClO₄ by TBP dissolved in a series of diluents confirmed that topological parameters, such as the Connectivity Index, CI, are useful for predicting the critical condition for phase splitting in different diluents. Based on the linear correlation between LOC values for HClO₄ and CI values of diluents, the effective Connectivity Index of the French nuclear reprocessing diluent, HTP, a complex mixture of highly branched alkanes, was determined.     

The mechanism for soluble phosphates to improve the water resistance of magnesium oxychloride cement

This paper discusses the reasons why the addition of some soluble phosphates to magnesium oxychloride cement (MOC) can greatly improve its water resistance. With the XRD analysis and the determination of the strength retention coefficients (a judging index for the water resistance), it has been shown that the addition of small quantity of the soluble phosphates, such as H₃PO₄, NaH₂PO₄·2H₂O, and NH₄H₂PO₄, to MOC pastes does not influence the phases formed in the MOC pastes, but can result in the great increases of the strength retention coefficients of hardened MOC pastes, i.e., the great improvement of the water resistance of MOC. It was considered that the key components being responsible for the improvement of the water resistance could be the anions H₂PO₄⁻, HPO₄²⁻, and PO₄³⁻ yielded by the ionization of these phosphates in the solution of MOC pastes. These anions can decrease the lowest concentration of Mg²⁺ ions in the solution required by the formation of 5Mg(OH)₂·MgCl₂·8H₂O (5-phase) or 3Mg(OH)₂·MgCl₂·8H₂O (3-phase) in the MOC pastes and increase the stability of these phases in water. Thus, when the hardened MOC pastes with small quantity of the soluble phosphates are immersed in water, the 5-phase or 3-phase in them will not be decomposed by water, which makes the strength of the hardened MOC pastes remain unchanged in water.     

Oxochloromolybdenum(V)tetraphenylporphyrin complex-containing polymer as a phosphate ion exchanger

Summary Oxochloro(5,10,15,20-tetraphenylporphyrinate)molybdenum (V) was physically entrapped into poly (styrene) by lyophilizing a benzene solution including both complex and polymer. The functional ability of the obtained complex-containing resin to adsorb H₂PO₄ ^– from an aqueous solution was investigated in the presence of various anions. It was found that the selectivity of the resin for H₂PO₄ ^– is superior to those of conventional anion exchangers.     

Electrical Aspects of Adsorbing Colloid Flotation. X. Pretreatments,Multiple Removals,Interferences, and Specific Adsorption

Abstract

The compatibility of the adsorbing colloid flotation of Cu(II) with Fe(OH)₃ and sodium lauryl sulfate with a variety of precipitation pretreatment techniques was studied. Procedures were developed which permitted precipitation pretreatment and effective foam flotation polishing. The interferences of glycerol, ClO₄ ^?, NO₃ ^?, C1^?, CN^?, CNS^?, F^?, SO4₄ ^2?, HPO₄ ^2?, HAsO₄ ^2?, C₂O₄ ^2?, (PO₃)₆ ^6?, and EDTA with the precipitate flotation of ferric hydroxide by sodium lauryl sulfate were studied. The simultaneous adsorbing colloid flotation of Cu(II), Pb(II), and Zn(II) with Fe(OH)₃ and sodium lauryl sulfate was found to be effective in the pH range 6 to 7 at ionic strengths below 0.1 mole/l. A model was analyzed for calculating surface potentials for floe surfaces having the charge distributed at discrete sites in the presence of electrolytes. Plots of surface potential versus adsorbable ion concentration were calculated for various values of the model parameters.     

Calcite Flotation in Potassium Oleate/Potassium Dihydrogen Phosphate System

Calcite flotation in acidic media is a difficult task due to the solubility of calcite and consequently the release of calcium ions in the flotation pulp. In addition, the interaction of calcium ions with the flotation reagents requires the correct selection of these reagents. In this study, potassium oleate and potassium dihydrogen phosphate (KH₂PO₄) were used as collector and depressant, respectively. Micro‐flotation experiments were conducted to probe the effect of these chemical reagents as well as their interaction on calcite flotation using H₂SO₄ as a pH regulator. In addition, to elucidate the depressing action of KH₂PO₄ on calcite, electrokinetic properties of calcite have been measured in relation to pH and in the absence and presence of KH₂PO₄. Moreover, thermodynamic calculations were used to rationalize the reasons for calcite depression as well as the adsorption mechanism of KH₂PO₄ onto the calcite surface.     

Crystallization kinetics of calcium nitrate tetrahydrate from MSMPR crystallizer

The steady-state crystal size distribution (CSD) of calcium nitrate tetrahydrate in both Ca(NO₃)₂H₂O and Ca(NO₃)₂H₃PO₄HNO₃H₂O systems were measured in a continuous mixed suspension mixed product removal (MSMPR) crystallizer at 19°C. The secondary nucleation rate (B°) and the growth rate (G) were correlated by a generalized semiempirical power law model. Freon-113 was found to be satisfactory for washing wet crystals of Ca(NO₃)₂·4H₂O separated from mother liquor. The influence of some impurities usually present in phosphate rock on B° and G were examined. The results showed that impurity ions increased generally the nucleation rate and inhibited, to some degree, growth rate. The sequence of effectiveness is: Al⁺³ > Mg⁺² > SiF₆⁻² > Fe⁺³.     

Spectroscopic,transport, and morphological studies of polyaniline doped with inorganic acids

A conducting polymer, polyaniline, was synthesized by chemical polymerization using different inorganic acids, such as HCl, H₂SO₄, HClO₄, HNO₃, and H₃PO₄, as protonic acid media. The synthesized polymers were characterized using UV‐visible and FT‐IR spectroscopy. A granular type of morphology was observed under SEM for HCl, HNO₃, and H₃PO₄ doped polyanilines. However, HClO₄ doped polyaniline shows the folded lamellar structure derived from the fibers. The thermal stability of these polymers was investigated with the help of thermogravimetric (TG/SDTA) analysis. The formation of a greater fraction of the conducting emeraldine salt phase is observed in HClO₄ as a protonic acid media. The thermal stability of H₃PO₄ doped material is found to be better as compared with other acids. An increase in conductivity with an increase in temperature was observed in all the samples except for HClO₄ doped polyaniline. Polym. Eng. Sci. 44:1676–1681, 2004. © 2004 Society of Plastics Engineers.     

Coatings of Conducting Polymers for Corrosion Protection of Mild Steel

The investigation of electrochemical behavior of different conducting polymers, polythiophene (PTh), polypyrrole (PPy) and polyterthiophene (PTTh) on a mild steel (MS) electrode were done. Moreover, the combinations of the conducting polymers PTh and PPy was investigated. The synthesis of all polymeric coatings was done by the cyclic voltammetry technique. The electrochemical impedance spectroscopy (EIS) measurements were used to evaluate the corrosion performance of coated mild steel by different polymers in 0.5 M of different acid solutions (HCl, HClO₄, H₂ C ₂ O ₄, H₃PO₄ and HNO₃). The protection of all polymeric coatings against corrosion of the substrate was promising and the bilayer coating PPy/PTh gave the best protection efficiency in all used acids. The order of efficiency for the different coatings in HCl and HNO₃ solutions was MS/PPy/PTh > MS/PPy > MS/PTTh > MS/PTh but the order in HClO₄, H₃PO₄ and H₂ C ₂ O ₄ solutions was MS/PPy/PTh > MS/PTTh > MS/PPy > MS/PTh.     

Determination of the promoting effect of nano SiO2 and H3PO4@nano SiO2 in the thiocyanation of N-containing aromatic compounds under solvent-free conditions

Silica nanoparticles/ammonium thiocyanate (nano SiO₂/NH₄SCN) and H₃PO₄ embedded on nano silica (H₃PO₄@nano SiO₂) in the presence of NH₄SCN were found to be effective systems for the thiocyanation of some arylamines and indoles to afford their corresponding thiocyanated adducts at 70°C under solvent-free conditions. The recovery and reusability of nano SiO₂ as a prompting system have been investigated. A simple procedure for the synthesis of H₃PO₄@nano SiO₂ has also been represented. In addition, a plausible mechanism of thiocyanation has also been suggested.     

Study on synthesis and electrochemical properties of novel ferrocene-based compounds and their applications in anion recognition

Two novel ferrocene-based compounds glycidyl ester of ferrocene carboxylate (GEFC) and 1,3-diferrocenecarboxylic acid diacylglycerol (DFCDG) were synthesized and characterized by ¹H NMR and mass spectrum. The influence of some factors, namely, solvent type, potential scan rate, electrolyte concentration and [Fe] unit concentration, on the electrochemical behaviors of two novel ferrocene-based compounds was investigated, and the mechanism of the electrode processes was studied. Finally, two compounds were applied to sense the H₂PO₄⁻ by cyclic voltammetry (CV) method and it was found that the DFCDG with a symmetric structure which was synthesized through ring opening reaction of ferrocene carboxylate and GEFC showed stronger interaction with the H₂PO₄⁻ than GEFC.     

The adsorption of sulphate, hydrogenchromate and dihydrogenphosphate anions on surfactant-modified clinoptilolite

The adsorption of sulphate, hydrogenchromate and dihydrogenphosphate anions on surfactant-modified clinoptilolite (SMC) was investigated. The SMCs were prepared by the adsorption of cis-1-aminoctadecen-9 (oleylamine) on both modified and unmodified natural clinoptilolite tuff. The properties of the modified clinoptilolite samples, such as cation type, structure of the zeolite framework and ECEC value, determined the mechanism of oleylamine adsorption, and consequently anion adsorption on the external clinoptilolite surface. According to the strength of the anion adsorption, two groups of SMCs could be distinguished: strong and weak anion adsorbents. Strong anion adsorbents were obtained by oleylamine adsorption on H⁺-clinoptilolites by protonation of the –NH₂ groups. This mechanism of oleylamine adsorption resulted in the surface precipitation mechanism of anion adsorption being the dominant mechanism. The oleylamine derivatives of Ca- and Na-clinoptilolite were weak anion adsorbents. Oleylamine is adsorbed on Ca- and Na-clinoptilolite by hydrogen bonding, thus yielding insufficient adsorption sites for anions. Hydrogenchromate and dihydrogenphosphate anions were nevertheless adsorbed on these SMCs by interaction with oleylamine. The experiments of anion adsorption on various oleylamine loaded SMCs confirmed the existence of two types of anion adsorption sites and showed that excess oleylamine did not significantly influence the anion adsorption in the investigated concentration range. The kinetic results showed that SO₄²⁻ and H₂PO₄⁻ adsorptions were slow processes while HCrO₄⁻ adsorption was completed in a few minutes.     

Extraction of some mineral acids by tri-n-octyl phosphine oxide

The distribution equilibria of hydrochloric, nitric, perchloric, sulphuric and phosphoric acids between aqueous solutions and a solution of tri-n-octyl phosphine oxide (TOPO) in organic solvents have been investigated. The organic phases were studied by infrared and nuclear magnetic resonance spectroscopy. As a result, it is found that the extraction of these acids is governed by the formation of HCl·TOPO, HNO₃·TOPO and HClO₄·TOPO, of H₂SO₄·2 TOPO and H₂SO₄·TOPO, and of H₃PO₄·3 TOPO, H₃PO₄·2 TOPO and H₃PO₄·TOPO, respectively.