Use of phytofiltration technologies in the removal of heavy metals: A review
J. L. Gardea-Torresdey, G. de la Rosa, and J. R. Peralta-Videa
Chemistry Department and Environmental Science and Engineering
Ph.D.
Program, University of Texas at El Paso, El Paso, TX 79968, USA
Abstract: Biosorption is a relatively new process that has proven
very promising in the removal of contaminants from aqueous effluents.
Microorganisms as well as plant- and animal-derived materials have been
used as biosorbents by many researchers. Biomaterial immobi-
lization and chemical modification improves the adsorption capacity
and stability of biosorbents. Biosorption experiments over Cu(II), Cd(II),
Pb(II), Cr(III), and Ni(II) demonstrated that biomass Cu(II) adsorption
ranged from 8.09 to 45.9 mg g1, while Cd(II) and
Cr(VI) adsorption ranged from 0.4 to 10.8 mg g1 and from 1.47
to 119 mg g1, respectively.
Mechanisms involved in the biosorption process include chemisorption,
complexation, surface and pore adsorption-complexation, ion exchange,
microprecipitation, hydroxide con-
densation onto the biosurface, and surface adsorption. Chemical modification
and spectroscopic studies have shown that cellular components including
carboxyl, hydroxyl, sulfate, sulfhydryl, phosphate, amino, amide, imine,
and imidazol moieties have metal binding properties and are therefore
the functional groups in the biomass. Column studies using support matrices
for biomass immobilization such as silica, agar, polyacrilamide, polysulfone,
algi-
nates, cellulase, and different cross-linking agents have been performed
to improve the biomass adsorption capacity and reusability. In this
review, the salient features of plant-derived
materials are highlighted as potential phytofiltration sources in the
recovery of toxic heavy and precious metals.
*Plenary lectures presented at the Inaugural Conference for the Southern and Eastern Africa Network of Analytical Chemists (SEANAC), Gaborone, Botswana, 7-10 July 2003. Other presentations are published in this issue, pp. 697-888.