Desorption and Extraction of Selected Heavy Metals from Soils

Abstract

The need for proper disposal of industrial wastes and for remediation methods for soils contaminated with heavy metals necessitates a better understanding of the processes involved in mobilizing, transporting, and retaining elements in surface soils. The objective of this study was to investigate the desorption in water and efficacy of several traditional extraction agents in removing Tc, Np, Mo, U, Cr, Pb, Cs, and Th. Selected slices were taken with depth in acidic sand (Dystrochrept) soil cores that were spiked for 4 yr. Similarly, Tc, Np, and U were desorbed and extracted from the clay subsoil of reed/sedge peat cores following a one‐season migration study. Technetium and Mo behaved as anions, and the small amount of Tc retained was attributed to insoluble organic complexes and oxides in the sandy soil and carbonates in the clay subsoil. The retention of Mo was attributed to colloidal Fe(III) oxides and organic colloids or complexes. Neptunium sorption appears to be dependent on the variable charge of the soil, making organic matter and pH important factors. Uranium and Pb were associated with the oxides. Cesium and Cr took part in inorganic reactions that fixed them rigorously to the soil solids or formed precipitates; Th formed organic complexes. Results suggest that remediation techniques for soils contaminated with Tc, Mo, and Np could be quite successful using intense leaching with acidified water. Soils containing U, Pb, and Th may be partially reclaimed by manipulation of the organic matter or leaching with organic acids; however, soils contaminated with Cs and Cr would require extensive chemical treatment.

Biogeochemical behavior of137Cs and60Co in tropical soils

“…In any case, it can be observed that iron oxides have an important role as a sink for l37 Cs (reducible and baste phases). Such behavior corroborates the findings of [15]. These authors obtained in four Canadian soil samples, using the sequential extraction method of Tessier, more than 40% of the total Cs associated with Fe and Mn oxides.…”

Effects of the mycorrhizal fungus Glomus intraradices on uranium uptake and accumulation by Medicago truncatula L. from uranium-contaminated soil

“…Plants take up U from the readily exchangeable and soluble fractions of the soil. However, according to previous work, negligible amount of U(VI) remain in the soluble and exchangeable forms over any significant time, thereby limiting the amount available for plant uptake and subsequent phytoremediation (Bunzl et al, 1995;Sheppard and Thibault, 1992). In addition, plant-associated microorganisms, including mycorrhizal fungi, may have significant effects on U uptake (Rufyikiri et al, 2002(Rufyikiri et al, , 2003(Rufyikiri et al, , 2004b.…”

Fracionamento de metais pesados em solo contaminado antes e após cultivo de arroz

“…Os óxidos de Fe e Mn são os principais adsorvedores de Pb nos solos. 28 A retenção de Pb aos óxidos de Fe é altamente específica (quimissorção) e o processo resulta na formação de complexos de esfera interna. 26 Isto faz com que este elemento seja pouco móvel nos solos, uma vez que as reações de quimissorção são menos reversíveis que as de troca iônica.…”