Irreversible sorption

Kan AT, G Fu, M Hunter, MB Tomson (1998) Irreversible sorption of nentral hydrocarbons to sediments experimental observations and model predictions. Environ Sci Technol 32 892-902. 

Arthur, S.E., Brady, P.V., Cygan, R.T., Anderson, H.L., Westrich, H.R. 1999. Irreversible sorption of contaminants during ferrihydrite transformation. WM 99 Conference, February 28-March 4. 

Despite this lack of degradation, the environmental significance of these compounds may be only minor, if preservation is accomplished by irreversible sorption to the sediments, which would render the A9PEO non-bioavailable. 

Hysteresis means that the slow state appears to fill faster than it empties. Many examples exist of apparent irreversible sorption of some fraction, or at least exceedingly long times to achieve desorption, following relatively short contact times. 

Other potential DOP isolation methods are based on sorption using anion-exchange resins or nonionic resins. Extensive research in concentrating humic material has employed these methods (55). For isolation and concentration of DOP, these techniques have several disadvantages, such as possible irreversible sorption onto the resins and the concentration of all anionic species present in the sample. Another major drawback is the need to use a strong base to remove the sorbed material from the resin. For sorption to occur with nonionic resins requires the protonation of all weak acids, thus exposing the sample to low pH. 

Solid-phase extraction could be coupled online with HPLC. This is becoming increasingly important, because it makes it possible to handle all the situations in which large series of samples have to be analyzed routinely, and therefore rapid, (semi-) automatic, and unattended analysis is an aspect of major concern. Moreover, sensitive trace level determination requires the analysis of total samples or sample extracts rather than aliquots, under conditions in which analyte losses, due to evaporation or irreversible sorption to the vessels walls, and contamination, caused by the solvent or reagents used, laboratory air, and/or sample manipulation in general, must be rigorously minimized (45,46). 

Ion exchange resin Specific ionic interaction, high capacity, large volumes possible Resin bleed, limited regeneration, irreversible sorption possible... 

Sorbent extraction Exclusion of salts Limited solubility of human matter, partly irreversible sorption... 

Alumina High sorption capacity, no organic bleed Irreversible sorption and chemical change of sorptive possible... 

Activated carbon High sorption capacity, chemical impurities Strong irreversible sorption, biofouling... 

This equation has been successfully applied to many sorption and desorption reactions of dissolved metals and organic compounds. In the case of irreversible sorption (hysteresis), sorption and desorption isotherms are not identical. However, both sorption and desorption Freundlich isotherm equations can be substituted into the transport equation(2) ... 

In most natural water, phosphine is very unstable and oxidizes even under anoxic conditions. Depending upon the redox potential of water, the oxidation products are diphosphine (P2H4), phosphorus, hypophosphorus acid, phosphorus acid, and phosphoric acid (Kumar et al. 1985). Based on soil studies (Berck and Gunther 1970 Hilton and Robison 1972), small amounts of phosphine may also be adsorbed (reversible sorption) or chemisorbed (irreversible sorption) to suspended solid and sediments in water. However, based on the estimated Henry s law constant (H) of 0.09 atm-m3/mol (see Table 3-3) and the expected volatility associated with various ranges of H, volatilization is expected to be the most important loss process for phosphine in water. 

The major drawbacks of the method are the possible loss of some elements by volatilization, contamination of the sample by airborne dust, as it must be left open to the atmosphere, and irreversible sorption of analyte into the walls of the vessel. It is important to do blanks with each batch of samples. Particles generated within the muffle furnace may be the cause of high or variable blanks. In this case the applicability of the method will depend on the level of analyte expected in the samples. A variable blank can be tolerated when the analyte level is substantially higher than the blank but not when the concentration analyte found in the blank and the sample are similar. 

Carbosieve S III Carboxenes Mainly gases 400 800 Strong or irreversible sorption of heavier molecules... 

Studies of the sorption of plutonium are complicated by the high redox reactivity of plutonium. Sorption of Pu(V) by pure aluminosilicates and oxyhydroxide phases is usually characterized by initial rapid uptake followed by slow irreversible sorption and may represent a reductive uptake mechanism catalyzed by the electrical double layer of the mineral surface (Turner et al., 1998 Runde et al., 2002a). In Yucca Mountain waters, the ranges for Pu(V) uptake by hematite, montmorillonite, and silica colloids were 4.9xl0 mLg to 1.8 X 10 mL g 5.8 X 10 mL and 8.1 X 10 mL g, respectively. These are much higher than those observed for Np(V) in the same waters as described previously. High surface redox reactivity for... 

Natural attenuation encompasses processes that lead to reduction of the mass, toxicity, mobility, or volume of contaminants without human intervention. The US EPA has recently published guidelines for the use of MNA for a variety of contaminated sites (US EPA, 1997). For inorganic constiments, the most potentially important processes include dispersion and immobilization (reversible and irreversible sorption, co-precipi-tation, and precipitation) (Brady et al, 1998). Studies of remediation options at UMTRA sites (Jove-Colon et al, 2001) and the Hanford Site (Kelley et al, 2002) have addressed the viability of adopting an MNA approach for uranium and strontium, respectively. As discussed below, different approaches are required to establish the viabihty of MNA for these radioelements. 

If the Langmuirian species are not in local equflibrium with the Henry s law species an additional retardation will result due to the kinetic limitation preventing equilibrium between Henry s law and Langmuirian molecules. Completly irreversible sorption would lead to trapping however, any reasonable non-zero rate of transfer between holes and matrix would be adiieved within some academically long time scale of desorption. These notions have been treated by Tshudy and von Frankenberg for the case of F = 0 and disarmed qualitatively by Koros and Hopfenberg for cases where 0 [Pg.116]

Nylon and 1. Efficient adsorption. 1. Irreversible sorption probable. 

Nonionic macropo- 1. Method is simple. 1. Irreversible sorption possible... 

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