Metal uptake properties

EXUDATES FROM ROOTS OF WILLOW CLONES WITH DIFFERENT METAL UPTAKE PROPERTIES... 

Mahmoud M.E. Comparison of metal uptake properties of silica gel-bound ion exchangers and some amine derivatives. Analytical Letters 1996 29 1791-1804. 

A batch equilibrium method, as a function of pH and shaking time, was performed to characterize the metal uptake properties of silica gel-immobiUzed-aminophenol and aminobenzoic acid. Studies were made and evaluated on the basis of column application of immobilized chelating sorbents for the removal of various metal ions from sugar cane molasses. These revealed that they have higher preference toward Mn(II), Fe(III), Co(II), Cu(II), and Zn(n) rather than alkali and alkaline earth metals.The structures of the modified silica gel phases are shown in Scheme 10. 

Soliman, E.M. Mahmoud, M.E. Metal uptake properties of sihca gel-immobilized aminophenol and aminobenzoic acid and their application for heavy metal removal from sugar cane molasses. Analusis 1997,25 (5), 148. 

The kinetics of metal sorption by sludges is rapid (Neufeld and Heiman, 1975 Nelson et al., 1981). Neufeld and Heiman (1975) concluded initially that metal sorption on sludges is not a biological phenomenon but is related to the physical and chemical properties of the sludge. Furthermore, they found that metal uptake was not affected by heavy metal concentration and organism viability. 

Kv is not a constant and may vary by several orders of magnitude. It is affected by element properties and both solid phase and pore water characteristics. Knowledge of the relationship between soil characteristics and Kp values enables the calculation of the distribution of heavy metals over the solid phase and pore water for different soils. When coupled to an uptake model for metals by biota that are directly or indirectly exposed via the pore water, the relationships for predicting Kp values may be used to predict metal uptake for these organisms on the basis of the metal concentration in the solid phase and some selected soil properties. The latter should, like the total concentrations, be easily determinable. 

Since colloidal material has both hydrophilic and lipophilic properties, making it permeable across membrane surfaces, lipid permeation may be an important mechanism for metal uptake. Lipophilic metals, such as organic Hg, have been shown to be taken up by... 

On the other hand, reactivity, bioavailability, and toxicity of Pt are not necessarily correlated with its total content, but depend also upon factors other than the soil properties and the metal-uptake kinetics of plants. Proteins are known to play... 

Inner-sphere complexes are relatively stable in comparison to outer-sphere complexes under equivalent solution conditions (i.e. pH, ionic strength), and in a competitive situation will tend to displace less stable adsorbates. This is a fundamental property of coordination reactions, and explains the observed trends in metal uptake preference observed in lichen studies (Puckett et al., 1973). Metal sorption results previously attributed to ion exchange reactions are more precisely described as resulting from competitive surface complexation reactions involving multiple cation types. Strictly speaking, each metal adsorption reaction can be described using a discrete mass law relation, such as... 

The general principles of metal uptake by biota from soil systems are treated in chapters 7 to 10 of the book. The same rules govern radionuclide uptake by biological systems. Uptake and assimilation depend on the chemical and biological properties of the element. The rate-limiting step for the uptake of many radionuclides, those strongly immobilized by soil constituents, is the movement to the interface between the soil solution and the biological membrane. If absorption is more rapid than the movement of the solute to the interface, uptake becomes diffusion limited. The adsorption properties of the soil are therefore determinant. 

The water moss F. antipyretica aceumulates metals in aquatie systems. This property ean be used to assess metal pollution of natural aquatie eeosystems. The biological variability of the plant material may have a significant influence on the accumulation capacity. Phenotype and age of the plants influence the metal uptake. Therefore active biomonitoring by exposing homogenous plant material has. 

Variations in the composition of root exudates may be one cause of difference in metal uptake between plant species and genotypes (Mench and Martin, 1991). It is important to investigate if the differences in accumulation capacities for metals by willow clones can be related to differences in rhizosphere processes. It is necessary to ask, therefore, how soil chemistry is influenced by the presence of willow roots, if soil chemistry varies between willow clones with properties of low and high metal accumulation and if the mechanisms are metal - or concentration - specific. 

Von Vugt et al., have studied the oxygen uptake properties of [RhCl(PRi3)3] in benzene solution as well as the catalytic oxidation of excess phosphine [121]. The rate of oxygenation of the metal complex, v, was expressed as shown in equation (75), in which Pq is the partial pressure of oxygen. 

The synthesized materials are usually characterized by a variety of chemical and physical properties. Chemical properties of the materials include pH dependency of metal uptake, maximum metal uptake capacity, acid-base characteristics, metal selectivity, and stability. Physical properties of the materials include mechanical strength and pore-network characteristics. A number of techniques discussed in the following section are employed to determine these properties. 

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