The Occurrence of Metals in Composted Municipal Wastes and Their Removal

The organic fraction of municipal wastes has been composted on the laboratory scale. In the obtained compost the content of cadmium, cobalt, copper, manganese, nickel, lead and zinc were determined, as well as the speciation i.e, the form of their occurrence, making use of Rudd's method of sequential extraction. The investigations also concerned the way of removing these metals from the compost by means of leaching with solutions of sulphuric and nitric acid, as well as by electrochemically separating the metals from the solution after the compost had been leached with sulphuric acid. It has been found that the application of the electrochemical method with varying pH values of the leaching solution within the range of 6.8–2.8 allows for the separation of 83.5% Cd, 55.0% Co, 65.4% Cu, 59.4% Mn, 70.3% Ni, 90.5% Pb and 56.2% Zn.