STRATEGY FOR LEACHING OF ZINC FROM ARTIFICIALLY CONTAMINATED SOIL

Extractability of zinc by sulphuric acid was studied using three diffe rent, artificially contaminated soil types at a pH range of 1.5-6. A s imple linear desorption was modified with respect to pH, resulting in high correlation indices. Aluminum solubilization was studied as an in dicator of damage of the soil matrix by the extraction. Zinc solubiliz ation increased monotonously with lowering pH within the whole pH-inte rval, however, only negligible aluminum solubilization was observed at pH above 3. Below this pH, Al-concentrations increased exponentially, whereas zinc extractability was not substantially improved. Therefore , the extraction process for removal of zinc from soil using mineral a cids should be optimised in respect to the maximum metal removal at mi nimum soil damage. The estimated amount of process water needed to cle an 1 kg of soil for Dutch standards was 2-10 litres, with concentratio ns varying from 10 to 50 mmoles of H2SO4 per litre of extractant.