Soil minerals metal sorption

McBride M.B. Processes of heavy and transition metal sorption by soil mineral. In Interactions at the Soil Colloid-Soil Solution Interface, G.H. Bolt, M.F. De Boodt, M.H.B.Hayes, M.B. McBride, eds. NATO ASI Series (Series E Applied Sciences-Vol 190). Dordrecht, Netherlands Kluwer Academic Publishers, 1991. 

McBride, M.B. (1991) Processes of Heavy and Transition Metal Sorption by Soil Minerals. Kluwer Academic Publishers, Dordrecht. 

Thus, witli time, one can see that metal sorption on soil minerals can often result in a continuum of processes from adsorption to precipitation to solid-phase transformation (Figure 3.10), particularly in the case of metals such as Co, Ni, and Zn. The formation of metal surface precipitates could be an important mechanism... 

Neubauer, U., Furrer, G., and Schulin, R. (2002). Heavy metal sorption on soil minerals affected by the siderophore desferrioxamine b the role Fe(ni) (hydr)oxides and dissolved Fe(III). Eur. J. Soil Sci. 53, 45-55. 

In accordance with modern theories, the main mechanism of metal sorption in various soils is the heterogenic surface sorption of metals by soil particles. In the sorption process, the various metals react with different functional groups of various soil compounds, like clay minerals, organic matter, oxides of Fe, Mn, Al, Si, etc. Various mechanisms of Me sorption in soil and soil solution are connected with various forms of their existence in soil such as exchangeable, specifically sorbed, occluded by oxides and hydroxides, bounded with organic matter and included into interlayer spaces of silicon minerals. In this study Tessier et al (1979) s method has been... 

Whether solid solutions actually do form in soils is probably limited more by slow rates of soil mineral dissolution—a necessary prehminary step for co-precipitation— than by lack of thermodynamic favorability. Although the overall impact of solid solution formation on metal solubility in soils remains to be determined, certain features of metal sorption are consistent with (but do not prove) sohd solution formation. These include a sorption capacity that is ill-defined and increasing with time, decreasing reversibility of sorption with time that follows a decreasing labihty of the... 

On the other hand, a classification of a sorption process on the basis of kinetics data must be conditioned by other chemical properties of the phosphate-soil mixture. For example, if the soil solution is supersaturated initially with respect to some phosphate solid, precipitation is likely to influence the sorption reaction from the beginning. If the soil minerals have a low degree of crystallinity and/or a high degree of hydration, precipitation may be the dominant sorption mechanism even in the rapid stage.In general, low phosphate concentrations and well-crystallized, relatively unhydrated soil minerals tend to favor adsorption as the phosphate reaction mechanism. Other chemical properties, such as the pH value of the soil solution and the kinds of metals in soil clay minerals, exert a quantitative influence on the rapid stage of phosphate sorption, as do such physical properties as temperature. ... 

Sorption reactions at the mineral/water interface significantly affect the mobility, speciation, and bioavailability of trace metal ions in aquatic and soil environments. Therefore, one must precisely understand the kinetics and mechanisms of metal sorption on mineral surfaces to accurately predict the fate of such pollutants in subsurface environments and to facilitate effective environmental remediation procedures. 

Metal sorption reactions on clay minerals, (hydr)oxides, humic substances and soils is usually characterized by a rapid, followed by a slow, reaction (Figure... 

The slow metal sorption step on many minerals and soils occurs over time scales of days and longer. This slow sorption has been ascribed to several mechanisms including interparticle or intraparticle diffusion in pores and solids, sites of low energy or reactivity, and surface precipitation/nucleation (49-51). 

Diffusion Mechanisms. Since minerals and soils are porous materials containing both macropores (>2nm) and micropores (<2nm) diffusion is a mechanism that can control the slow rate of metal sorption (Figure 6). These pores can be inter-particle (between aggregates) or intra-particle (within an individual particle). 

It has been proposed that the extent to which mixed-cation hydroxide compounds actually do form in aquatic and terrestrial environments is limited more by slow rates of soil mineral dissolution, a necessary preliminary step, than by lack of thermodynamic favorability (57). Because the dissolution rates of clays and oxide minerals are fairly slow, the possibility of mixed-cation hydroxide formation as a plausible "sorption mode" in 24 hour-based sorption experiments (and also most long-term studies) containing divalent metal ions such as Mg, Ni, Co, Zn, and Mn and Al(III)-, Fe(III)-, and Cr(III)-(hydr)oxide or silicate minerals has been ignored in the literature 16,17). This study and others recently published (77), however, suggests that metal sorption onto mineral surfaces can significantly destabilize surface metal ions (A1 and Si) relative to the bulk solution, and therefore lead to an enhanced dissolution of the clay and oxide minerals. Thus, predictions on the rate and the extent of mixed-cation hydroxide formation in aquatic and terrestrial environments based on the dissolution rate of the mineral surface alone are not valid and underestimate the true values. 

The studies of Scheidegger et al. 16,17) have emphasized the importance of combining time-dependent or kinetic studies with spectroscopic and microscopic investigations to better understand sorption processes at the soil mineral/water interface. Such studies can result in a detailed mechanistic understanding (e.g., distinguishing the rate of metal adsorption versus precipitation processes in sorption systems) which would be difficult to determine using a macroscopic approach alone. 

Investigating the sorption of Pb, Cu, and Zn to samples of several horizons of forest soils (Sipos et al. 2008,2009), Cu and Pb were found to have higher and stronger sorption on the studied samples than Zn. Only the former two metals showed significant differences in their immobilized metal amounts on the studied samples and soil mineral particles. Copper and zinc sorbed mostly on soil mineral constituents, whereas lead was associated mainly to SOM. Highest metal amounts were sorbed on the swelling clay mineral particles (smectites and vermiculites). Alkaline conditions due to the carbonate... 

Sipos, R, T. Nemeth, V. K. Kis, and I. Mohai. 2009. Association of individual soil mineral constituents and heavy metals as studied by sorption experiments and analytical electron microscopy analyses. Journal of Hazardous Materials 168, no. 2-3 1512-1520. doi 10.1016/j.jhazmat.2009.03.033. 

For metal desorption from the biomass certain dilute solutions of mineral acids like hydrochloric acid, sulfuric acid, acetic acid and nitric acid were used [219, 76]. Batch system was carried out to study the desorption of the adsorbed Hg (II) from the biosorbent - immobilized and heat inactivated Trametes versicolor and Pleurotus sajur-caju [8]. Hg (II) ions adsorbed onto the biosorbents were eluted with 10 mmol dm HCl and the results showed that more than 97% of the adsorbed Hg (II) ions were desorbed from the biosorbents. In order to evaluate the feasibility of applying the prepared biosorbents in the heavy metals removal processes, the metal desorption efficiency from loaded biosorbents, and the reusability of the biosorbent in repeated adsorption-desorption operations were determined. The charged species exhibited desorption-resistance fraction whereas the desorption of the neutral form was completely reversible. The difference in sorption and desorption between the neutral and charged species is attributed to the fact that the anionic species sorbs by a more specific exothermic adsorption reaction whereas the neutral form partition by the hydrophobic binding to the soil [206]. Desorption of soil-associated metal ions and possible mechanisms have received considerable attention in literature [148],... 

---