Organic matter adsorption mechanisms

Arnarson,T. S., and Keil, R. G (2000). Mechanisms of pore water organic matter adsorption to montmorillonite. Mar. Chem. 71, 309-320. 

Adsorption-desorption Partly Mechanisms for adsorption on similar materials will be similar. Soil adsorption data generally do not reflect the saturated conditions of the deep-well environment. Organic-matter content is a major factor affecting adsorption in the near-surface its significance in the deep-well environment is less clear. Fate studies involving artificial recharge are probably useful, but differences between fresh waters and deep brines may reduce relevance. 

In summary, the removal of organic matter and Fe oxides significantly changes the physicochemical and surface chemical properties of soils. Thus, this pretreatment affects the overall reactivity of heavy metals in soils. The removal of organic matter and Fe oxides may either increase or decrease heavy metal adsorption. The mechanisms responsible for the changes in metal adsorption in soils with the removal of organic matter and Fe oxides include increases in pH, surface area, CEC and electrostatic attraction, decreases in the ZPC, shifts of positive zeta potentials toward... 

Keywords. Sorption, Interaction mechanisms, Organic pollutants, Solid phases, Adsorption, Partitioning, Humic substances, Humus, Organic matter... 

Retention of organic contaminants on subsurface solid phase constituents in general is not completely reversible, so that release isotherms differ from retention isotherms. As a consequence, the extent of sorption depends on the nature of the sorbent. Subsurface constituents as well as the types of bonding mechanisms between contaminants and the sohd phase are factors that control the release of adsorbed organic contaminants. Saltzman et al. (1972) demonstrated the influence of soil organic matter on the extent of hysteresis. Adsorption isotherms of parathion showed hysteresis (or apparent hysteresis) in its adsorption and desorption in a water solution. In contrast, smaller differences between the two processes were observed when the soils were pretreated with hydrogen peroxide (oxidized subsamples) to reduce initial organic matter content. The parathion content of the natural... 

A hydrophobic bonding mechanism is the result of an overall entropy gain of the system due to the displacement of water molecules from the clay surface by sorbed organic compounds. The contributions of this mechanism will be more pronounced in the adsorption of high-molecular-weight organic matter (Parfitt and Greenland, 1970 Mortland, 1970). 

Gu, B., Schmitt, J., Chen, Z., Liang, L., and McCarthy, F. (1994). Adsorption and desorption of natural organic matter on iron oxide Mechanisms and models. Environ. Sci. Technol. 28,38—46. 

The mechanism and extent of adsorption are ascertained to depend on several factors, which include (a) the physical and chemical nature and properties of both HS and organic xenobiotic and (b) the conditions of the medium. Organic matter in organic amendments is relatively fresh or little humified, has composition and properties that differ substantially from native soil HS, and affects the composition and structure of native soil HS. Therefore, organic xenobiotics added to soils interact with a complex mixture of applied and native HS, which is expected to affect both quantitative and mechanistic aspects of adsorption phenomena. 

It may be best to consider this bacterial-mechanical hypothesis for the formation of laminated aragonitic odids as a precursor to more recent models, where adsorption of organic matter on odid surfaces influences the precipitation of CaC03. 

Indicates the pore space available for water and roots influenced by soil composition (mineral content, mineral type, and organic matter) and soil texture Affects adsorption of the chemical Affects the surface area where adsorption can take place Influences partitioning and availability of chemicals Affects ability of a soil to transmit water or air Dictates the porosity of the soil Affects the form, reactivity, solubility, availability, and toxicity of some contaminants Affects the toxicity of some substances (mainly heavy metals) with binding or antagonistic mechanisms, for example, by alkaline-earth metals and aluminum Organic matter content, type, and % carbon Influences soil sorption properties for heavy metals and... 

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