EVALUATION OF THE HEAVY METAL IMMOBILIZATION POTENTIAL OF PINE BARK-BASED COMPOSTS

Composts have the potential for remediating heavy metal-contaminated soils. This sorption study investigated the potential of composted pine bark (PB) and its co-composts with goat manure (PBG) and sewage sludge (PBS) to immobilize lead [Pb (II)], copper [Cu (II)], zinc [Zn (II)] and nickel [Ni (II)]. The Langmuir maximum sorption capacity (q(max)) of the composts followed the order PBG >> PBS > PB for the tested metal ions. The q(max) values of PBG compost followed the order Cu (II) > Pb (II) > Zn (II) > Ni (II) whereas for PB and PBS composts they followed the order Pb (II) > Cu (II) > Zn (II) > Ni (II). Increasing solution pH improved the Cu and Zn retention capacities of the acidic PB and PBS composts but had no effect on the nearly neutral PBG compost. Thus, the PBG compost had better metal immobilization capacity than the PB and PBS composts, which may require liming to improve their effectiveness.