Sorption/desorption metals

Pigna M, Krishnamurti GSR, Violante A (2006) Kinetics of arsenate sorption-desorption from metal oxides Effect of residence time. Soil Sci Soc Am J 70 2017-2027... 

In order to test the reversibility of metal-bacteria interactions, Fowle and Fein (2000) compared the extent of desorption estimated from surface complexation modeling with that obtained from sorption-desorption experiments. Using B. subtilis these workers found that both sorption and desorption of Cd occurred rapidly, and the desorption kinetics were independent of sorption contact time. Steady-state conditions were attained within 2 h for all sorption reactions, and within 1 h for all desorption reactions. The extent of sorption or desorption remained constant for at least 24 h and up to 80 h for Cd. The observed extent of desorption in the experimental systems was in accordance with the amount estimated from a surface complexation model based on independently conducted adsorption experiments. 

A.J. (ed.) Aqueous environmental chemistry of metals. Ann Arbor Sci., 193-217 Giammar, D.E. Hering, J.G. (2001) Time scales for sorption-desorption and surface precipitation of uranyl on goethite. Environ. Sci.Techn. 35 3332-3337 Gilkes, R.J. Suddhiprakarn, A. (1979) Biotite... 

Many of the early studies on kinetics of soil chemical processes were obviously concerned with diffusion-controlled exchange phenomena that had half-lives (r1/2) of 1 s or greater. However, we know that time scales for soil chemical processes range from days to years for some weathering processes, to milliseconds for degradation, sorption, and desorption of certain pesticides and organic pollutants, and to microseconds for surface-catalyzed like reactions. Examples of the latter include metal sorption-desorption reactions on oxides. 

Tien (1987) studied the kinetics of heavy metal sorption-desorption on sludge using the stirred-flow reactor method of Carski and Sparks (1985). Sorption-desorption reactions were rapid with an equilibrium reached in 30 min. The sorption-desorption reactions were reversible. The sorption rate coefficients were of the order Hg > Pb > Cd > Cu > Zn > Co > Ni, while the desorption rate coefficients were of the order Cd > Cu > Hg >... 

Metal hydride element is a complex physical item, which can be described by the continuum theory equations. There are three basic processes i) process of hydrogen filtration through a porous hydride matrix and heat-conducting inserting, ii) processes of heat application and heat abstraction from a space of hydrogenation and iii) chemical processes accompanying hydrogen sorption - desorption. 

Vasudevan, D., Cooper, E. M., and Van Exem, O. L. (2002). Sorption-desorption of lonogenic compounds at the mineral-water interface study of metal oxide-rich soils and pure-phase minerals. Environ. Sci. Technol. 36, 501-511. 

The variations in pH at lower depths were attributed to various factors in addition to the associations with P treatment sources at the top. This included redox conditions associated with fluctuations in the water table, lower levels of CO2 compared to those on the surface, and possibly the effects of sorption-desorption of metals during leaching. 

---