EXTRACTABILITY OF CADMIUM, COPPER AND ZINC FROM CONTAMINATED BIOMASS USING NTA (NITRILOTRIACETIC ACID)

Activated sludges and cells of the bacterium Pseudomonas fluorescens were contaminated with metals Cd, Cu, Zn during and after growth phase. P. fluorescens contaminated after growth (cells suspended in distilled water + metals) accumulated 16.8 mg.g(-1) of cadmium, 2.2 mg.g(-1) of copper and 8.6 mg.g(-1) of zinc. P. fluorescens contaminated during growth (bacteria;grown in liquid nutritive medium + metals) accumulated 5.6 mg.g(-1) Cd, 2.7 mg.g(-1) Cu and 1.1 mg.g(-1) Zn. These contaminated materials were used to estimate comparatively the removal of the accumulated metals by 1 mM NTA, EDTA and DTPA (shaking 10 mg of biomass with the chelatant solution at pH 6.5 for 3 hours). NTA was chosen among the three as the more efficient extractant. Metals were removed with NTA in order to measure the amount of readily extracted metals from contaminated P. fluorescens cells and to evaluate the maximal fraction of metal that could be removed from activated sludges. NTA removed over 90% of accumulated metal by P. fluorescens contaminated after growth, but only 50% of that accumulated during the growth, and just 10% of the metal from activated;sludges. This suggests that activated sludge cannot be readily cleaned before application to agricultural land.