Chemical Interactions between Mercurial Species and Surface Biomolecules
3
Biosorption and Bioaccumulation on the Surface of
Biological Structures
161
All over the world, restrictive environmental legislations, as well as the approach
given for the new scenarios on environmental questions, envisage new directions
for environmental problems. Based on this assumption, new trends in the
development of biologically based technologies for the decontamination of heavy
metals solutions are being defined.
The high cost associated with the development of technologies for treatment of
heavy metal-containing solutions, and the increasing dispersion of toxic
elements in soils and water streams, is stimulating the development of new
treatment processes, based on the natural ability of biological materials to
accumulate such elements. Such biological materials range from microbial
species to higher plants, also including biopolymeric substances.
These heavy metal accumulation processes are primarily based on the
biomolecular apparatus of different kinds of materials. These biological materials
include micro algal strains (da Costa and Leite 1993; Cordery et al. 1994; da Costa
et al. 1994; Ting et al. 1995), bacteria (Beveridge and Murray 1976, 1980; Macaskie
et al. 1995; Hu et al. 1996), fungi (Brunker and Bott 1974; Brady et al. 1994),
cyanobacteria (Garnham et al. 1993a, b), inactivated seaweeds (Volesky 1994;
Winter et al. 1994; Volesky and Holan 1994; da Costa et al. 1996; da Costa and de
Franya 1996a,c, 1997; Nestle and Kimmich 1996), as well as mixed immobilized
materials (da Costa and de Franya 1996b).
It must be emphasized that the previously mentioned metal sorbers were
tested under very particular closed systems, in which fixed operational and
experimental conditions for the uptake were adopted; it does not mean that
under different environmental conditions the biological material would act in a
similar manner.
In natural environments such as lakes, rivers, soils and oceans, several other
physico-chemical parameters must be considered, and not only the biological
incorporation of toxic metals. For instance, adsorption of the metals by bottom
sediments and particulate materials, remobilization of toxic metals, speciation of
the metal as a function of the environmental conditions, all these parameters
markedly contribute to enhance or to inhibit any specific biological metal uptake.
However, any heavy or essential metal ready to interact with any biological
material would do so through surface components, primarily. Thus, it is very
important to have an overview on these surfaces, because these act as the
primary sites for metal accumulation, and this primary interaction will dictate
further steps in the sorption process.
The complexity with which this first incorporation takes place will depend on
several factors, of biological as well as of physicochemical nature. This primary
interaction of toxic metals with surface structural biological components has
already been termed metal biosorption to describe passive metal uptake, occurring
owing solely to the chemical composition ofliving cells or those inactivated by any
3
Biosorption and Bioaccumulation on the Surface of
Biological Structures
161
All over the world, restrictive environmental legislations, as well as the approach
given for the new scenarios on environmental questions, envisage new directions
for environmental problems. Based on this assumption, new trends in the
development of biologically based technologies for the decontamination of heavy
metals solutions are being defined.
The high cost associated with the development of technologies for treatment of
heavy metal-containing solutions, and the increasing dispersion of toxic
elements in soils and water streams, is stimulating the development of new
treatment processes, based on the natural ability of biological materials to
accumulate such elements. Such biological materials range from microbial
species to higher plants, also including biopolymeric substances.
These heavy metal accumulation processes are primarily based on the
biomolecular apparatus of different kinds of materials. These biological materials
include micro algal strains (da Costa and Leite 1993; Cordery et al. 1994; da Costa
et al. 1994; Ting et al. 1995), bacteria (Beveridge and Murray 1976, 1980; Macaskie
et al. 1995; Hu et al. 1996), fungi (Brunker and Bott 1974; Brady et al. 1994),
cyanobacteria (Garnham et al. 1993a, b), inactivated seaweeds (Volesky 1994;
Winter et al. 1994; Volesky and Holan 1994; da Costa et al. 1996; da Costa and de
Franya 1996a,c, 1997; Nestle and Kimmich 1996), as well as mixed immobilized
materials (da Costa and de Franya 1996b).
It must be emphasized that the previously mentioned metal sorbers were
tested under very particular closed systems, in which fixed operational and
experimental conditions for the uptake were adopted; it does not mean that
under different environmental conditions the biological material would act in a
similar manner.
In natural environments such as lakes, rivers, soils and oceans, several other
physico-chemical parameters must be considered, and not only the biological
incorporation of toxic metals. For instance, adsorption of the metals by bottom
sediments and particulate materials, remobilization of toxic metals, speciation of
the metal as a function of the environmental conditions, all these parameters
markedly contribute to enhance or to inhibit any specific biological metal uptake.
However, any heavy or essential metal ready to interact with any biological
material would do so through surface components, primarily. Thus, it is very
important to have an overview on these surfaces, because these act as the
primary sites for metal accumulation, and this primary interaction will dictate
further steps in the sorption process.
The complexity with which this first incorporation takes place will depend on
several factors, of biological as well as of physicochemical nature. This primary
interaction of toxic metals with surface structural biological components has
already been termed metal biosorption to describe passive metal uptake, occurring
owing solely to the chemical composition ofliving cells or those inactivated by any