Organic complexes of iron and aluminium in natural waters

Nature ◽  
1976 ◽  
Vol 260 (5550) ◽  
pp. 418-420 ◽  
Author(s):  
EDWARD M. PERDUE ◽  
KEVIN C. BECK ◽  
J. HELMUT REUTER
Keyword(s):  
Natural Waters ◽  
Organic Complexes

scholarly journals The Solubility and Hydrolysis of Aqueous Aluminium Hydroxides in Dilute Fresh Waters at Different Temperatures

1990 ◽  
Vol 21 (3) ◽  
pp. 195-204 ◽  
Author(s):  
Espen Lydersen
Keyword(s):  
Natural Waters ◽  
Equilibrium Constants ◽  
Relative Concentration ◽  
Amorphous Solid ◽  
Effect Of Temperature ◽  
Natural Soil ◽  
Exchange Reactions ◽  
Organic Complexes ◽  
Inorganic Species ◽  
Different Temperatures

This study is mainly focusing on the effect of temperature and pH on the chemistry of Al(OH)3(s) using available thermodynamic data. The calculations show that a doubling of the [H+] or a decrease in temperature by 15°C, approximately yields the same solubility increase of the various Al(OH)3(s) presented. The relative concentration of aqueous aluminium hydrolysis complexes is also highly temperature dependent. At 25°C and pH 5, the calculated distribution of dissolved, inorganic aluminium hydroxides corresponds to about 36% of Al3+, 37 % of Al(OH)2+, 26 % of Al(OH)2+ and 1 % of Al(OH)30. At the same pH but at 0°C, about 84%, 13%, 2% and 0% are present as Al3+, Al(OH)2+, Al(OH)2+ and Al(OH)30, respectively. This temperature effect is of major importance as the hydroxide species are supposed to be the most toxic species to aquatic biota. Literature reports on the equilibrium constants Al(OH)3(s), log*Ks, vary from about 8 to 11, a variation in the product by a factor of 1000. In natural soil/water systems the solubility products of crystalline and amorphous solid aluminium sources are unknown and the solubility may also be coupled to combined weathering/ion exchange processes. In addition substantial amount of aluminium may be present as organic complexes where aluminium by cation exchange reactions may enter the solution as monomeric inorganic species. Thus, if a low value for the equilibrium constants of Al(OH)3(s) is used as reference when calculating the degree of aluminium saturation, an apparent oversaturation will often be demonstrated. To estimate the degree of aluminium saturation in natural waters whould therefore only be of theoretical interest.

Chemical Speciation of Environmentally Significant Metals: An IUPAC contribution to reliable and rigorous computer modelling

2015 ◽  
Vol 37 (1) ◽  
Author(s):  
Kipton J. Powell ◽  
Paul L. Brown ◽  
Robert H. Byrne ◽  
Tamas Gajda ◽  
Glenn Hefter ◽  
...  
Keyword(s):  
Metal Ions ◽  
Natural Waters ◽  
Chemical Speciation ◽  
Computer Modelling ◽  
Adsorbed Species ◽  
Mineral Phases ◽  
Organic Complexes ◽  
Anionic Ligands ◽  
Ligand Species ◽  
Metal Ligand

The mobility and bioavailability of metal ions in natural waters depend on their chemical speciation, which involves a distribution of the metal ions between different complex (metal-ligand) species, colloid-adsorbed species and insoluble phases, each of which may be kinetically labile or inert. For example, in fresh water the metal ions are distributed among organic complexes (e.g., humates), colloids (e.g., as surface-adsorbed species on colloidal phases such as FeOOH), solid phases (e.g., hydroxide, oxide, carbonate mineral phases), and labile complexes with the simple inorganic anionic ligands commonly present in natural waters (e.g., for Zn

Studies of metal–organic interactions in model systems pertaining to natural waters

1976 ◽  
Vol 54 (16) ◽  
pp. 2600-2611 ◽  
Author(s):  
Robert D. Guy ◽  
C. L. Chakrabarti
Keyword(s):  
Humic Acid ◽  
Organic Acids ◽  
Stability Constants ◽  
Tannic Acid ◽  
Natural Waters ◽  
Model Systems ◽  
Organic Complexes ◽  
Metal Organic ◽  
Acid Release ◽  
The Stability

The interactions of Cu(II), Pb(II), Cd(II), and Zn(II) with humic and tannic acids were studied to evaluate the possibility of metal speciation using a combination of dialysis/atomic absorption spectroscopy, and the pH characteristics of the metal–organic species. The stability constants of metal–organic complexes were found to decrease in the order Pb(II) > Cu(II) > Cd(II) > Zn(II) and EDTA > humic acid > tannic acid. Scatchard plots for the metal–humic acid systems indicated two types of binding sites with a difference in stability constants of about 10. Ultrafiltration of metal–humic acid solutions indicated that the metal ions were concentrated in the large molecular size fractions (> 3.1 nm). Separation by dialysis was used to investigate the release of metal from model sediment components by the organic acids (the metal–organic complexes were non-dialyzable). For release of copper from bentonite, it was found that the amount of copper released depended on both the concentration of ligand and the stability constant of metal complex, with the ratio of metal release to complexing sites decreasing in the order EDTA > humic acid > tannic acid. Release of metal from the solids decreased in the order: bentonite > MnO2 > humic acid. Release of metal from the hydrous oxides via a redox decomposition of the oxide by natural organics was investigated using pyrogallol, gallic, and tannic acids. At natural water pH levels (6–8), 20 μg/ml solutions of the organic acids released 20 μmol manganese per 100 ml solutions whereas at pH 2, 60 μmol manganese were released. The pH behaviour of the organic acids has been explained in terms of formation of oxalic acid at pH &([a-z]+); 5, which then reduces the hydrous oxide.

The Application of a Simple Chemical Model of Natural Waters to Metal Fixation in Particulate Matter

1975 ◽  
Vol 53 (5) ◽  
pp. 661-669 ◽  
Author(s):  
Robert D. Guy ◽  
C. L. Chakrabarti ◽  
Laurier L. Schramm
Keyword(s):  
Humic Acid ◽  
Natural Waters ◽  
Anodic Stripping Voltammetry ◽  
Copper Ion ◽  
Freundlich Isotherm ◽  
Stripping Voltammetry ◽  
Differential Pulse ◽  
Chemical Model ◽  
Organic Complexes ◽  
Simple Chemical

A simple chemical model was used to investigate the mechanisms controlling the distribution of metals between soluble and particulate fractions in natural waters. The model particulates used were potassium bentonite, hydrous MnO2, and solid humic acid. The soluble species in natural waters were modelled by soluble humic acid, tannic acid, and bicarbonate. The sorption curves for Cu(II), Cd(II), and Zn(II) onto humic acid and MnO2 obeyed Langmuir adsorption isotherms whereas the sorption of the above ions onto bentonite followed a Freundlich isotherm. Chemical analysis of the total model using atomic absorption spectroscopy and differential pulse anodic stripping voltammetry indicated that copper distribution depends on the pH of the suspension: above pH 6.0, 50 % of the copper is sorbed onto the particulates whereas the copper in solution is in a complexed form; between pH 6 and 3.8 the soluble copper is distributed between organic complexes and "free" copper ion; between pH 4.2 to 2.5 copper is being desorbed from the particulates; and below pH 2.5 all the copper is present in solution as "free" copper ion.

THE MECHANISM OF NITRATES TRANSFORMATION IN THE PROCESSES OF ELECTROCHEMICAL TREATMENT OF NATURAL WATERS

2002 ◽  
Vol 1 (3) ◽  
pp. 341-346
Author(s):  
Viorica Iambartev ◽  
Gheorghe Duca ◽  
Maria Gonta ◽  
Vera Matveevici
Keyword(s):  
Natural Waters ◽  
Electrochemical Treatment
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