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

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