Sorption and precipitation of iron on kaolinite. III. The solubility of iron(III) hydroxides precipated in the presence of kaolinite

Soil Research ◽  
1970 ◽  
Vol 8 (1) ◽  
pp. 107 ◽  
Author(s):  
AW Fordham
Keyword(s):  
Electron Microscope ◽  
Solubility Product ◽  
Reaction Times ◽  
Ionic Species ◽  
Total Iron ◽  
X Ray ◽  
Acidic Solutions ◽  
Ph Values ◽  
Solubility Products ◽  
Ph Range

Iron(111) hydroxides were precipitated upon kaolinite suspended in acidic solutions of either 0.15M NaCl or 0.15M NaClO4. The progress of the reaction was followed for up to 15 weeks by periodic measurements of pH values and total iron(111) concentrations in solution. Total iron(m) concentrations varied from 1 0 - 3 ~ to 2 x 10-7 and pH values from 2.2 to 4.4. In NaCl media, steady state conditions were reached within 4-5 weeks. Allowing for the various iron(III) ionic species present in the solution phase, the solubility product *K++S2 (= [Fe(OH)+2]/aH+) was found to be 4.9 x 10-3 (S.D. = 0.7 x 10-3 log*K++S2 = - 2.31; log Kso = - 38.9). Although the initial precipitates were amorphous, the presence of �-FeOOH in aged suspensions was detected by X-ray analysis, in agreement with electron microscope observations. In NaClO4 media, the solubility of precipitates decreased rapidly during the first 3 weeks and relatively slowly thereafter. Although equilibrium was obviously not established within 5 weeks and possibly not within 15 weeks, values of solubility products, constant over the whole pH range, were derived from results at both reaction times. For suspensions aged for 5 weeks, *K++S2 was 4.85 x 10-3 (S.D. = 0.75 x 10-3 ; logKso = -38.9), whilst for those at 15 weeks, *K++S2 was 2.45 x 10-3 (S.D. = 0.3 x 10-3; log Kso = -39.2). X-ray and infra-red analyses and electron microscope examination indicated the presence of lepidocrocite in the aged products. There was no evidence that either the type or the solubility of products formed on aging was influenced by the presence of kaolinite, although the clay accelerated the rate of crystal growth.

Characterisation of Metal Binding Sites for 8-Azaguanine and 8-Azahypoxanthine Derivatives Synthesis and X-Ray Structural Analysis of Methylmercury(II) and Zinc(II) Complexes

1986 ◽  
Vol 41 (9) ◽  
pp. 1117-1122 ◽  
Author(s):  
W. S. Sheldrick ◽  
P. Bell
Keyword(s):  
Structural Analysis ◽  
Binding Site ◽  
Metal Binding ◽  
Binding Sites ◽  
Antineoplastic Agent ◽  
X Ray ◽  
Metal Binding Sites ◽  
Ph Values ◽  
Ph Range

Abstract The complexes [(CH3Hg)AGuaH ] (1) and [(CH3Hg)2AGua] • H2O (2) have been isolated from aqueous 1:1 and 2:1 solutions of CH3HgOH and 8 -azaguanine (AGuaH2) at respective pH values of 5 and 9. Only one CH3Hg+ complex of 8 -azahypoxanthine (AHxH2), namely [(CH3Hg)2AHx] (3), could be isolated under analogous conditions. X-ray structural analyses established N1 and N9 as metal binding sites in 3 and N9 as the coordination position in [Zn(H2O)4(AHxH)2] (4). With 8-aza-9-benzylhypoxanthine (9-BzAHxH) only one CH3Hg+ complex [(CH3Hg)9-BzAHx] (5) could be isolated in the pH range 2-10. N1 was established by X-ray structural analysis as the binding site. The relevance o f these findings to an understanding of ligand behaviour of the antineoplastic agent 8 -azaguanine is discussed.

Solubility Products of Aluminum Hydroxide in Various Ionic Solutions

1973 ◽  
Vol 51 (21) ◽  
pp. 3528-3533 ◽  
Author(s):  
David T. Y. Chen
Keyword(s):  
Aluminum Hydroxide ◽  
Aluminum Chloride ◽  
Solubility Product ◽  
Ionic Solutions ◽  
Chloride Solutions ◽  
Ion Concentrations ◽  
Ph Values ◽  
Solubility Products ◽  
Low Solubility

Solubility products of Al(OH)3 were determined in various solutions of NH4+, Li+, Na+, K+, and Ca2+ ions. Increasing amounts of these hydroxides were added to the respective chloride solutions containing aluminum chloride. The solutions were aged for 3 months. Activities of the OH− ions were calculated from the pH values of the solutions. The total Al concentrations remaining in solutions were determined by Hsu's modified aluminon method. The Al3+ ion concentrations were computed using the hydrolysis equilibria of Aveston. The ion product, aAl3+(aOH−)3, was found to vary linearly with the [OH]/[Al] ratio. The solubility product of Al(OH)3 was obtained by extrapolating this ratio to 3. The pKsp values thus obtained were 30.55, 33.15, 30.75, 30.36, and 31.00 in NH4+, Li+, Na+, K+, and Ca2+ systems respectively. The anomalously low solubility product of Al(OH)3 in the Li+ system was attributed to the specific "lithium effect".

Single Phase Pyrite Synthesized via Hydrothermal Method

2013 ◽  
Vol 562-565 ◽  
pp. 136-140 ◽  
Author(s):  
Zhao Tang Yang ◽  
Xiao Jiang Liu ◽  
Jing Song Liu ◽  
Xiu Li Feng
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Hydrothermal Method ◽  
Single Phase ◽  
Sem Images ◽  
X Ray ◽  
Decreasing Ph ◽  
Size And Morphology ◽  
Ph Range ◽  
Scanning Electron

Single phase pyrite has been successfully prepared via the reaction of FeSO4·7H2O, S and Na2S·9H2O using hydrothermal method. The X-ray powder diffraction measurements confirm the formation of iron disulfides in the pH range of 1-12. Marcasite is formed at pH<4, the marcasite contents in the final products increasing with decreasing pH; when the pH is higher than 4, the final product is single phase pyrite. Scanning electron microscope (SEM) images reveal that both the pH and temperatures have significant effects on the size and morphology of final products. Pyrite micro-nanocubes of 200-400nm in length were synthesized at pH=9. Detailed information of the experimental results are analyzed in the results and discussion part.

Study on Stability of AgI/TiO2 Visible Light Photocatalysts in Solutions of Various pH Values

2011 ◽  
Vol 399-401 ◽  
pp. 1272-1275
Author(s):  
Lu Feng ◽  
Ke Feng He ◽  
Wan Ping Chen
Keyword(s):  
Visible Light ◽  
Absorption Edge ◽  
Ph Value ◽  
Alkaline Treatment ◽  
Alkaline Solutions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Acidic Solutions ◽  
Ph Values ◽  
Vis Spectroscopy

Nanostructured AgI/TiO2 photocatalysts exhibit highly efficient visible light photocatalytic activity. Though there have been extensive investigations on AgI/TiO2 photocatalysts, study on their stablity is still very limited. So in this paper, such a study is designed and conducted. AgI/TiO2 nanostructured photocatalysts were prepared and separately immersed in HCl solutions, DI water and NaOH solutions with pH value of 0, 4, 7, 10 and 14, respectively. X-ray diffraction and diffusive reflectance UV-vis spectroscopy analyses reveal that the immersion in acidic solutions led to the formation of AgCl and a blue shifting to 450nm for the absorption edge of AgI/TiO2, while the alkaline treatment had no significant effect on the composite structure of AgI/TiO2 or on the UV-vis absorption edge. Photocatalytic tests show that immersion in acidic solutions had more significant influence on AgI/TiO2 photocatalytic degradation of methyl orange (MO). At pH = 4, photocatalytic efficiency was dropped nearly 30%. At pH = 10, no significant change was observed. AgI/TiO2 nanostructured photocatalysts have thus been found to display a higher stability in alkaline solutions than in acidic solutions.

scholarly journals Synthesis of Novel Azo-Linked 5-Amino-Pyrazole-4-Carbonitrile Derivatives Using Tannic Acid–Functionalized Silica-Coated Fe3O4 Nanoparticles as a Novel, Green, and Magnetically Separable Catalyst

2021 ◽  
Vol 9 ◽  
Author(s):  
Farhad Sedighi Pashaki ◽  
Mohammad Nikpassand
Keyword(s):  
Electron Microscope ◽  
Tannic Acid ◽  
Reaction Times ◽  
X Ray ◽  
H Nmr ◽  
Transmission Electron ◽  
Magnetically Separable Catalyst ◽  
Elemental Analyses ◽  
Ft Ir ◽  
High Yields

Tannic acid–linked silica-coated Fe3O4 nanoparticles (Fe3O4@SiO2@Tannic acid) were prepared and characterized by transmission electron microscope (TEM), field emission scanning electron microscope (FE-SEM), X-ray powder diffraction (XRD), X-ray spectroscopy (EDX), vibrating sample magnetometry (VSM), and Fourier transform infrared (FT-IR) spectroscopy. Fe3O4@SiO2@Tannic acid supplies an environmentally friendly procedure for the synthesis of some novel 5-amino-pyrazole-4-carbonitriles through the three-component mechanochemical reactions of synthetized azo-linked aldehydes, malononitrile, and phenylhydrazine or p-tolylhydrazine. These compounds were produced in high yields and at short reaction times. The catalyst could be easily recovered and reused for six cycles with almost consistent activity. The structures of the synthesized 5-amino-pyrazole-4-carbonitrile compounds were confirmed by 1H NMR, 13C NMR, and FTIR spectra, and elemental analyses.

scholarly journals Synthesis and solubility of brompyromorphite Pb5(PO4)3Br

Mineralogia ◽  
2012 ◽  
Vol 43 (1-2) ◽  
pp. 129-135 ◽  
Author(s):  
Urszula Janicka ◽  
Tomasz Bajda ◽  
Maciej Manecki
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Solubility Product ◽  
X Ray Diffraction ◽  
Ph Measurements ◽  
X Ray ◽  
Ph Values ◽  
Free Energy Of Formation ◽  
Scanning Electron ◽  
Energy Of Formation

AbstractThe bromide analogue of pyromorphite Pb5(PO4)3Br was synthesized and characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. The solubility of the brompyromorphite was measured at 25°C and pH values of 2.0, 2.6 and 3.2. For the 3 pH measurements, the average solubility product, log KSP, for the reaction Pb5(PO4)3Br ⇔ 5Pb2+ + 3PO- 3- + Br- at 25ºC is -77.38 ± 0.70. The free energy of formation, ΔG°f,298, calculated from this measured solubility product is -3724.7 ± 4.3 kJ mol−1. These results confirm that brompyromorphite is more soluble than pyromorphite.

Preparation and Structural Characterization of Methylmercury(II) Complexes of 5-Aza- and 6-Azauracil Derivatives

1987 ◽  
Vol 42 (12) ◽  
pp. 1556-1562 ◽  
Author(s):  
W. S. Sheldrick ◽  
S. Heeb
Keyword(s):  
Structural Analysis ◽  
Binding Sites ◽  
Ionic Complex ◽  
X Ray ◽  
H Nmr ◽  
Ph Values ◽  
Nmr Data ◽  
Wide Ph Range ◽  
Ph Range

Abstract1:1 Methylmercury(II) complexes of the anti-tumour agent 6-azauracil (6AUH2) and its deriva­tives 6-azathymine (6ATH2). 1-methyl-6-azauracil (6AMUH) and 1-methyl-6-azathymine (6AMTH) have been isolated from aqueous solutions of CH3HgOH and the respective base. N3-Coordination was established by X-ray structural analysis for both [(CH3Hg)6 AUH] (1) (pH 6-8) and [(CH3Hg)6 AMT] (5) (pH 4-12); in addition 1H NMR data are in accordance with an identical binding site in the complexes [(CH3Hg)6AMU] (3) and [(CH3Hg)6 ATH] (4). Using an excess of CH3HgOH. 2:1 complexes with N1, N3-coordination may be prepared for both 6 AUH: and 5 AUH2 in a wide pH range (4-12 and 6-12 respectively). At pH values of 3-4 a 3:1 complex [(CH3Hg)35 AU]NO3 (7), with N1, N3, N5-coordination may be isolated: the binding sites were confirmed by X-ray structural analysis. In no case could an ionic complex with N6- coordination be isolated for a 6-azapyrimidine derivative. The binding preferences of the bases are discussed in the light of MNDO calculations.

scholarly journals Effects of pH on the stability of cyanidin and cyanidin 3-O-β-glucopyranoside in aqueous solution

2015 ◽  
Vol 69 (5) ◽  
pp. 511-522 ◽  
Author(s):  
Violeta Rakic ◽  
Mihaela Skrt ◽  
Milena Miljkovic ◽  
Danijela Kostic ◽  
Dusan Sokolovic ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Visible Range ◽  
Colour Intensity ◽  
Colour Variation ◽  
Acidic Solutions ◽  
Absorbance Maximum ◽  
Ph Values ◽  
Effects Of Ph ◽  
The Stability ◽  
Ph Range

The colour variation, colour intensity and stability at various pH values (2.0, 4.0, 7.0 and 9.0) of cyanidin 3-O-?-glucopyranoside (Cy3Glc) and its aglycone cyanidin was investigated during a period of 8 hours storage at 25?C. Our data showed that pH of aqueous solution had impact on spectroscopic profile of cyanidin and Cy3Glc. Beginning with the most acidic solutions, increasing the pH induce bathochromic shifts of absorbance maximum in the visible range for all examined pH values (with the exception pH 4.0 for cyanidin), while the presence of the 3-glucosidic substitution induce hypsochromic shift. Compared to cyanidin, Cy3Glc has higher colour intensity and higher stability in the whole pH range, except at pH 7.0. The 3-glucosidic substitution influences on the colour intensity of Cy3Glc in the alkaline region. After 8-hour incubation of Cy3Glc and cyanidin at pH 2.0 and 25 ?C, 99% of Cy3Glc and only 27% of cyanidin remained unchanged.

Sorption and precipitation of iron of Kaolinite. II. Sorption isotherms and their interpretation in terms of Iron(III) ionic equilibria

Soil Research ◽  
1969 ◽  
Vol 7 (3) ◽  
pp. 199 ◽  
Author(s):  
AW Fordham
Keyword(s):  
Iron Concentration ◽  
Ferric Hydroxide ◽  
Sorption Isotherms ◽  
Ionic Species ◽  
Total Iron ◽  
Polymerization Process ◽  
Quasi Equilibrium ◽  
Clay Surface ◽  
Ionic Equilibria ◽  
Ph Range

The sorption of iron(III) by kaolinite was studied in different media as a function of iron concentration, pH, and time, with such low concentrations of total iron that precipitation was excluded over most of the pH range examined. The reaction continued at a measurable rate for several weeks but a state of quasi-equilibrium, independent of the medium and of clay : solution ratio, was achieved in about 1 week. The amount of iron sorbed from the most acidic solutions was relatively low but increased markedly with increasing pH. Total iron concentrations measured in equilibrium with the clay were resolved by computer into concentrations of the component ionic species, which were then plotted against the total amount of iron sorbed. Unique relationships were found within specified pH ranges. From pH2O to 2.7, the amount of iron sorbed was correlated with the concentration of the species FeOH2+ and, from about pH 2.7 to 3.6, with the concentration of Fe(OH)2+. Specific sorption of these species by the clay is discussed. At higher pH values and prior to the precipitation of iron, other factors contributed to the sorption of iron. A reaction of monomeric iron species from solution with iron already sorbed by the clay is proposed, leading to the formation of polymers on the clay surface. Under suitable conditions of iron concentration and pH, precipitation of ferric hydroxide, probably a later stage of the polymerization process, occurred on the clay surface, in accordance with a well-defined solubility product relationship.

The ageing of sesquioxide gels. II. Alumina gels

1962 ◽  
Vol 33 (257) ◽  
pp. 145-157 ◽  
Author(s):  
R. C. Mackenzie ◽  
R. Meldau ◽  
J. A. Gard
Keyword(s):  
Electron Microscope ◽  
Room Temperature ◽  
Aluminium Chloride ◽  
X Ray ◽  
High Ph ◽  
Ph Values ◽  
Gel Particles ◽  
Infra Red ◽  
Alumina Gels ◽  
Temperature Ageing

SummaryAluminium oxides occur widely in soils and are of considerable pedological significance. The ageing of alumina gels, prepared from aluminium chloride and ammonia, into crystalline hydroxides has been investigated using thermal, X-ray, infra-red, and electron-microscope techniques. At room temperature ageing is more rapid at high pH values. The structure of the original gel particles appears to resemble boehmite and ageing causes the formation of bayerite with small amounts of gibbsite. The morphology of the various mineral types is considered and a mechanism of ageing suggested.

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