Extraction of Heavy Metals from a Contaminated Soil by Using Chelating Agents

For the experimental study, solutions of EDTMP, NTA, and TA were selected for HM extraction. The influence of extraction time and the ratio of extractant concentrations on extraction efficiency was evaluated. The analysed soil was artificially contaminated with selected HM (Cu, Zn, Pb). Chemical extraction of HM using chelating agents resulted in a reduction of HM concentrations in the soil to the permissible limit values set by the Council Directive 86/278/EEC. The most suitable chelating agents under the conditions of this experiment were the combined chelating agents NTA and TA with an extraction time of 60 minutes. Cu and Zn concentrations were reduced to permissible limits even when using the lowest concentration of NTA and TA (0.1 M), while the 0.5 M concentration and 60-minute extraction time resulted in the lowest concentrations of Cu, Zn, and Pb in the soil - 48 mg/kg, 74 mg/kg, and 78 mg/kg, respectively - and the highest extraction efficiencies of 93.3 %, 91.1 %, and 95.2 %, respectively. The combined chelating agents NTA and TA showed higher extraction efficiencies than the synthetic organic chelating agent NTA alone at different extraction times. The variation in extraction efficiency for the different combined chelating agents is presented as follows: for NTA and TA (0.5 M:0.5 M), Pb > Cu > Zn, and for EDTMP and TA (0.5 M:0.5 M), Cu > Pb > Zn. For chelating agents of synthetic origin only, the series were: NTA - Cu > Zn > Pb, and EDTMP - Cu > Pb > Zn.