Analisis Organico Elemental

Journal of Colloid and Interface Science 277 (2004) 1–18
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Feature article

Adsorption of heavy metal ions on soils and soils constituents
Heike B. Bradl ∗
Department of Environmental Engineering, Umwelt-Campus Birkenfeld, University of Applied Sciences Trier,
P.O. Box 301380, 55761 Birkenfeld, Germany
Received 16 December 2003; accepted 1 April 2004Available online 24 April 2004

Abstract
The article focuses on adsorption of heavy metal ions on soils and soils constituents such as clay minerals, metal (hydr)oxides, and soil organic matter. Empirical and mechanistic model approaches for heavy metal adsorption and parameter determination in such models have been
reviewed. Sorption mechanisms in soils, the influence of surface functional groups andsurface complexation as well as parameters influencing adsorption are discussed. The individual adsorption behavior of Cd, Cr, Pb, Cu, Mn, Zn and Co on soils and soil constituents is reviewed.
 2004 Elsevier Inc. All rights reserved.
Keywords: Adsorption; Soil; Heavy metals; Clay minerals; Metal (hydr)oxides; Soil organic matter; Cd; Cr; Pb; Cu; Mn; Zn; Co

1. Introduction
Soil is one of thekey elements for all terrestric ecosystems. It provides the nutrient-bearing environment for plant
life and is of essential importance for degradation and
transfer of biomass. Soil is a very complex heterogeneous
medium, which consists of solid phases (the soil matrix)
containing minerals and organic matter and fluid phases (the
soil water and the soil air), which interact with each other
andions entering the soil system [1]. The ability of soils to
adsorb metal ions from aqueous solution is of special interest and has consequences for both agricultural issues such as
soil fertility and environmental questions such as remediation of polluted soils and waste deposition.
Heavy metal ions are the most toxic inorganic pollutants
which occur in soils and can be of natural or ofanthropogenic origin [2]. Some of them are toxic even if their concentration is very low and their toxicity increases with accumulation in water and soils. Adsorption is a major process
responsible for accumulation of heavy metals. Therefore the
study of adsorption processes is of utmost importance for
the understanding of how heavy metals are transferred from
a liquid mobile phase to the surface ofa solid phase.
The most important interfaces involved in heavy metal
adsorption in soils are predominantly inorganic colloids such
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E-mail address: h.bradl@umwelt-campus.de.
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doi:10.1016/j.jcis.2004.04.005

as clays [3], metal oxides and hydroxides [4], metal carbonates and phosphates. Alsoorganic colloidal matter of detrital
origin and living organisms such as algae and bacteria provide interfaces for heavy metal adsorption [5–8]. Adsorption
of heavy metals onto these surfaces regulates their solution
concentration, which is also influenced by inorganic and organic ligands. Those ligands can be of biological origin such
as humic and fulvic acids [9–11] and of anthropogenic originsuch as NTA, EDTA, polyphosphates, and others [12–15],
which can be found frequently in contaminated soils and
wastewater.
The most important parameters controlling heavy metal
adsorption and their distribution between soil and water are
soil type, metal speciation, metal concentration, soil pH,
solid: solution mass ratio, and contact time [16–20]. In general, greater metal retention andlower solubility occurs at
high soil pH [21–25].
To predict fate and transport of heavy metals in soils both
conceptual and quantitative model approaches have been developed. These models include the determination of the nature of the binding forces, the description of the chemical
and physical mechanisms involved in heavy metal–surface
reactions and the study of the influence on variations of...