Presence Of Carbonate Ions Research Articles

Formation of Uniform Lanthanum(III) Carbonate Hydroxide Particles in the Presence of 1,2-Ethanediamine and Their Conversion into Oxides

Abstract Uniform spherical particles of crystalline lanthanum(III) carbonate hydroxide were prepared by aging at 100 °C the corresponding 1,2-ethanediamine complex solution in the presence of carbonate ion under specified conditions. The latter anions were generated from a mild oxidation of the ligand with nitrate ions present. The carbonate hydroxide particles were completely converted into the oxides at 900 °C without deformation.

Effect of anions on the sorption of uranyl ions on hydrous oxides: Application of the surface hydrolysis model

The sorption of uranyl ions on hydrous titanium oxide (HTiO), thorium oxide (HThO) and magnetite (MAG) has been studied in the presence of NO 3 −, Cl −,SO 4 2− and CO 3 2− as a function of pH and anion concentration at a total ionic strength of 0.1 mol dm −3. The distribution of surface hydroxyl groups in different forms and the surface pH have been evaluated from pH-titration curves in the presence of varying anion concentrations. An enhancement in sorption and a shift of the sorption isotherm to lower pH were observed on HTiO in the presence of 0.001 mol dm −3 SO 4 2− compared to 0.1 mol dm −3 ClO 4 −. In 0.1 mol dm −3 SO 4 2− the sorption isotherm is shifted to higher pH on all oxides. Chloride and nitrate ions do not significantly affect the uranyl sorption. At low pH and low SO 4 2− concentration, the enhanced uranyl sorption on HTiO could be explained in terms of the surface hydrolysis model by taking into account the formation of (UO 2) 2(OH) 2SO 4 in solution and dimer-like structures resembling this species on the oxide surface. At higher SO 4 2− concentrations and low pH, the sorption of uranium on HTiO involves the species UO 2(SO 4) 2 2− the oxide surface acting as an anion exchanger. In the presence of carbonate ions, the oxide surfaces act as cation exchangers, and uranyl sorption involves the breaking up of anionic carbonate complexes, a process which depends upon the surface acidity and capacity.

The Influence of Iodine on the Immunological Properties of Thyroglobulin and its Immunological Complexes

Several papers described different immunological properties of thyroglobulin (Tg) after iodination. The influence of iodine-iodide solution on the immunological properties of hTg and its immunological complexes with autoantibodies (aAbs) were studied. Human Tg coated to polystyrene plates, incubated for 30 min with iodine-iodide solution at concentration from 1 to 200 microM at pH 9.0 lost its ability to bind aAbs. Preincubation with iodine (2 microM), decreased aAbs binding by 50%. Tg epitope inactivation induced by iodine depended on the buffer pH and the presence of carbonate ions. The binding of rabbit Tg-antibodies to iodine pretreated Tg was only slightly changed. Thyroglobulin preincubation with iodine solutions decreased aAbs binding from all tested sera (67) of patients with autoimmune thyroid disease (AITD). Excess of iodide (0.2 M KJ) or equimolar concentration of diiodotyrosine protects the Tg molecule from iodine induced inactivation. Immunological complexes of Tg with aAbs dissociate at low iodine concentrations. The results suggest that a product of iodine disproportionation reaction induces changes in the Tg molecule and Tg-aAb's complexes leading to complex dissociation or epitope inactivation.

Phosphorus Release in Sodium Ion Dominated Soils

AbstractCalcareous sodic soils having high sodicity and high pH often maintain high solution P concentration. The effect of high exchangeable Na, high pH, and alkali anions and carbonates on the release of inorganic P was investigated in soils representing the three major benchmark sodic soil series found in the Indo‐Gangetic plains of India. Sodium saturation of the exchange complex, high pH, carbonate ions, and low electrolyte level shifted the solid P‐solution P equilibrium in favor of maintenance of high P concentrations in aqueous solutions. In the sodic soil environment, release of P can be accounted for by the dissolution of various forms of Ca‐P compounds at high alkalinity and pH. Cultivation of alkali soils improves the organically bound P forms. Together or in combination, high sodicity, high pH, and the presence of carbonate ions at low salinity markedly increased P desorption and P availability in sodic soils.

Association of poly-(L-lysine) homologues in sodium carbonate solution

The molecular weights of isopoly(L-Iysine), poly(L-ornithine), and poly(L-α, γ-diaminobutylic acid), the homologues of poly (L-lysine), were determined by the sedimentation equilibrium method in aqueous solutions of 1.0 M NaCl or 0.1 M Na2CO3. In every sample the molecular weights in the presence of carbonate ions was twice that in NaCl solution. In a previous paper we reported that poly(L-lysine) behaved as a dimer at concentrations higher than 0.4 g/dl in the presence of carbonate ions and as a monomer in dilute solution, and these two forms were related by a monomer-dimer equilibrium. The homologues did not have a monomer-dimer equilibrium relationship under the conditions of the measurements that we carried out. The CD spectrum of isopoly(L-lysine) in water showed a uniform increase with a decrease in the wave length in the presence of carbonate ions. However, in the alkaline region in NaOH solution, the spectrum changed and a small minimum at 212 nm was found. When additional carbonate ions were added a large minimum at 205 nm was observed. This result can be explained by a change in the conformation from a random coil to a regular structure. We could not compare isopoly(L-lysine) with other polypeptides, because it does not have peptide bonds. The CD spectra of poly(L-ornithine) and poly(L-α, γ-diaminobutylic acid) in NaOH or Na2CO3 solutions showed only slightly regular structures. It was also confirmed that the dimer-structures of the poly (L-lysine) homologues do not have regular structures.

The Role of HPO 42− and CO 32− Ions in the Transformation of Synthetic Apatites to β-Ca 3(PO 4) 2

The simultaneous effect of HPO 4 2− and CO 3 2− ions on the thermal decomposition of synthetic carbonated apatites to β-tricalcium phosphate has been studied. The apatites were prepared under different pH conditions and with different carbonate concentrations and were then heated with and without CaHPO 4·2H 2O up to 1100°C. The products were studied by infrared, Fourier transform infrared, and x-ray diffraction methods. The results showed that when HPO 4 2− is present in the system (preparation at low pH or addition of CaHPO 4), β-Ca 3(PO 4) 2 formed below 700°C and that decomposition was slower or was prevented totally in the presence of carbonate ions.

Influence of salt addition on the hydrothermal conversion of rhyolitic pumice into zeolite

The influence of the presence of anions in zeolite synthesis systems starting from rhyolitic pumice has been examined. The anions may play a double role, sometimes determining the formation of certain phases (mainly feldspathoids), in other cases favouring or disfavouring the growth of a species at kinetic level (zeolite Na-P). A novel phase (denominated K), the formation of which is dependent on the presence of carbonate ions, has been obtained and described. The possibility that the valence more than the nature of the anions in the parent solution may be effective in accelerating the growth of some phases is emphasized.

Factors influencing the selective leaching of molybdenum with sodium hypochlorite from copper/molybdenum sulphide minerals

The leaching of molybdenite and copper sulphides with solutions of hypochlorite has been studied. The roles of pH and additions of carbonate ion in controlling molybdenum extraction and hypochlorite decomposition are described. The presence of carbonate ions during leaching prevents loss of molybdenum through precipitation as calcium molybdate. Carbonate ions while increasing copper extraction appear to act as stabilizers for the hypochlorite by delaying the onset of precipitation of catalytically active copper compounds. The leaching of molybdenite-containing copper sulphide rougher concentrates, it is concluded, is best performed at pH 9 with a carbonate-containing hypochlorite solution. Theoretical consideration is given to the possible influence of cadmium, zinc and lead ions on molybdenum extraction during the leach.

Nmr studies on complex formation of poly(L‐lysine HBr) with carbonate ion in aqueous solution

AbstractDiemer formation of poly(L‐lysine HBr) in carbonate buffer at pD 10.5 was reported in our previous paper [Biopolymers(1981) 20, 345–357]. The mechanism of the dimer formation was investigated employing carbon‐13 and proton nmr. pD dependence of the 13C‐nmr spectrum of poly(L‐lysine HBr) in the presence of carbonate ion clearly shows that a complex formation between the CO ion and protonated ε‐amino group is involved in the stabilization of the dimer form. The lifetime of the complex is longer than 10−2 s. A stoichiometric evaluation suggests that CO bridges two lysyl side chains. A molecular model of the dimer form designated as a single antiparallel β‐ribbon was proposed and discussed in the light of hydrodynamic and ir spectroscopic properties reported earlier. Concentration change experiments indicate that CO binds not only to the dimer formation is inferred as stabilization of the single antiparallel β‐ribbon as an intermediate structure in the conversion between the α‐helix and β‐sheet. The α‐CH proton signal of the lysine residue located in the ordered structure (α‐helix and β‐form) was observed to be separate from that in the random‐coil region.

Solubility of Hydroxyapatite

MUCH research has been devoted to the solubility of hydroxyapatite, Ca10(PO4)6(OH)2, and a large number of solubility constants have been reported. They are, however, inconsistent and, according to van Wazer1, vary over a range of 1011. A complicating factor seems to be the presence of small quantities of carbonate; thus Greenwald2 and Ericsson3 found that in the absence of carbonate the solubility of hydroxyapatite obeyed the solubility product principle, but it did not obey this principle in the presence of carbonate ions. Greenwald attributed the increase of solubility in the presence of carbonate ions at high pH to the formation of complex ions in the solution, but this reaction would not account for the decrease in solubility found by Ericsson at low pH.