The role of compost properties in sorption of heavy metals

The feasibility of various composts to operate as sorbents for heavy metals (Cu and Zn) removal from wastewater has been evaluated. Three commercial composts obtained from municipal solid wastes (MWS), sludge sewage (SS) and poultry manure (PM) were selected as potential sorbents. Kinetic and equilibrium tests were conducted in order to assess the equilibrium conditions to remove metals from aqueous samples. For all composts, the maximum time necessary to reach the equilibrium was 240 min. The Freundlich and Langmuir isotherm models were found to fit the sorption data. The SS compost proved to be the one with highest removal capability for both assessed metals, while MWS compost showed to be the less suitable for this purpose. These results can be explained in terms of the compost surface properties, namely, with the cation exchange capacity.