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June 1973
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12 Reads
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36 Citations
Geoderma
Formation constants for Cu2+ complexes with humic and fulvic acids were determined by a modification of the well-known Bjerrum potentiometric titration method. Highly stable complexes were formed with formation constants of the order of those observed for synthetic polycarboxylic acids. Overall formation constants for a two-step process (B2) ranged from 2.5 · 10−4 to 7.9 · 10−3.
November 1972
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10 Reads
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49 Citations
Soil Science Society of America Journal
Calculation methods based on Schubert's ion‐exchange equilibrium method were developed for determining stability constants of metal‐soil organic matter complexes. The methods, which were free of certain assumptions and errors inherent in the ion‐exchange technique as applied previously to soil organic matter, were verified using Mn(II)‐citrate and Mn(II)‐oxalate systems. Apparent stability constants (log K) of Zn (II)‐humic acid complexes ranged from 3.13 to 5.13 at pH 6.5.
January 1972
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76 Reads
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300 Citations
... While in practical wastewater treatments, recognizing the detailed composition by current technologies is quite difficult because the composition of wastewater is highly complicated, and the characterization of target species will be seriously affected by the many coexisted substances. In early studies, the complexation features were often characterized by physicochemical experiments such as complexometric titration, ion exchange and stripping voltammetry, which make it difficult to acquire the exact coordination circumstance of heavy metals [147][148][149][150][151]. To deal with above problems, a reasonable strategy is to fractionate the raw wastewater into several fractions whose composition is relatively simple, thereby making the analysis of each fraction easier because of the mitigated interference from background substances. ...
June 1973
Geoderma
... The affinities of HSs for copper have long been well recognised, and Stevenson's initial work in the field involved the potentiometric titration of SOM in the presence of transition metals (Khanna and Stevenson 1962), and he and colleagues later studied formation constants of Cu 2+ complexes with HAs and FAs . Various techniques were used in the complexation studies, such as potentiometric titration (Stevenson 1977;Stevenson and Chen 1991), using the response characteristics of the Cu(II) ion-selective electrode; ligand concentration effects (Fitch et al. 1986) and the application of a discrete-site/electrostatic ion-binding model (Tipping et al. 1995 (Stevenson 1966(Stevenson , 1976a, and the procedures used for the determinations involved a modified ion-exchange technique (Ardakani and Stevenson 1972), a comparison of models for determining the stability constants (Fitch and Stevenson 1984;Stevenson et al. 1993) and conditional stability constants and the nature of reactive sites for Ag + -HSs complexes . ...
November 1972
Soil Science Society of America Journal
... Available Zn concentrations decrease by 100-fold with a unit increase in soil pH (Havlin et al., 2013). Soil organic matter can maintain micronutrients in soil solution via chelation, with several micronutrients forming stable complexes with SOM (Stevenson and Ardakani, 1972). Consistently high correlations between Zn avail and soil organic matter have been reported in semi-arid agroecosystems (Follett and Lindsay, 1970;Miner et al., 2018). ...
January 1972
