Biomedical Engineering Reference
In-Depth Information
7
Comparative Metal Ion Binding to Native
and Chemically Modified
Datura innoxia
Immobilized Biomaterials
Gary D. Rayson and Patrick A. Williams
Department of Chemistry and Biochemistry
New Mexico State University, Las Cruces, NM
USA
1. Introduction
Removal of toxic heavy metal ions from contaminated water is required to provide safe
drinking water. This can be effected either within the waste stream at contaminate source or
at point of use. Incorporation of remediation technologies at either location requires the
removal of pollutants at parts per million and parts per billion concentrations from water
containing more benign metal ions (e.g., Ca
2+
, Mg
2+
, and Na
+
) at concentrations three to six
orders of magnitude higher. Materials derived from plants or microorganisms (e.g., algae
and fungi) have been shown to enable the reduction of trace concentrations of heavy metal
ions to below regulatory limits (Davis, et al., 2003).
Such nonliving biomaterials have been reported to have exhibit high capacity, rapid
binding, and selectivity towards heavy metals (Drake and Rayson, 1996). It is postulated
that functional groups native to the lipids, carbohydrates, and proteins found in the cell
walls of the biomaterial are responsible for uptake (biosorption) of metal ions (Gardea-
Torresdey, et al., 1999; 2001; Drake and Rayson, 1996; Drake, et al., 1997; Kelley, et al., 1999).
For biomaterials to become a commercially viable method of metal remediation and
recovery these functional groups must be identified and their contribution to overall metal
binding capacity quantified. Knowledge of such informaiton would allow either simple
chemical alteration to the biomaterial, allowing for targeting of specific metals, or an
enhancement of biomaterial metal binding.
Significant progress has been made to identify the chemical functionalities involved in the
biosorption of numerous metal ions by a variety of plant and algal tissues (Gardea-
Torresdey, et al., 1999; 2001; Riddle, et al., 2002; Fourest and Volesky, 1996; Drake, et al.,
1997;Jackson, et al., 1993). Several techniques have been reported to probe local chemical
environments of biosorbed metal ions. These have included X-ray absorption (Gardea-
Torresdey, et al., 1999; Riddle, et al., 2002), lanthanide luminescence (Drake, et al., 1997;
Serna, et al., 2010), and metal NMR (Xia and Rayson, 1996; 2002; Kelley, et al., 1999; Majidi,
et al., 1990) spectroscopy. Analysis of total metal ion binding isotherm data modeling
(Volesky, 2000) has also been described. Efforts to address the chemical heterogeneity of
those biosorbed materials have also employed regularized regression analysis of isotherm
data (Lin, et al., 1996). Additionally, these chemical intensities have been studied through
selective removal of binding moieties by their reactive modification (Drake, et al., 1996).
