Measurements were made of the adsorption of lead, cadmium, zinc, nickel and uranium per unit surface area of microorganisms, two clays (reference smectite, kaolinite), and two soils (untreated Vertisol and treated Vertisol) to quantify the selective affinity. The adsorption of heavy metals and uranium by the samples was influenced by soil constituents, and increased with increasing Pb, Ni, Zn, Cd and U concentrations. Microorganisms were also compared with these abiotic soil constituents for their ability to adsorb these metals. Dead cells adsorbed the largest quantity of all heavy metals than live cells and other soil components. At pH 6.0, the uptake percentage of U(VI) by dead cells was higher than that of any of the other metal ions. On the basis of amounts of adsorption on adsorbents, the selectivity sequences were varied. The most common sequences were U>>Pb>Cd≈Zn>Ni. The results verified the importance of geochemical parameters of soils such as type of clay mineral, oxide mineral content, and organic content, for controlling metal uptake. The results also suggest that bacterial membrane cells can be successfully used in the treatment of mixed metal-contaminated wastes.
- Heavy metal