EFFECTS OF DIFFERENT PASSIVATING MATERIAL TREATMENTS ON MORPHOLOGICAL CHANGES OF HEAVY METALS BEFORE AND AFTER COMPOSTING

摘要

This study explores the effects of different passivating materials on the immobilization of Cu, As, Zn, Cd and Pb in cocontaminated waste composting. The multimaterial composting experiment was conducted by mixing pig manure, chicken manure, garden litter and urban sludge at a ratio of 20:55:10:15 (W/W) to investigate the effects of adding superphosphate, calcium carbonate or their combination on the forms of heavy metals before and after composting. The results reveal that adding passivating materials immobilized Cu, Zn, Cd, Pb differently and activated As. Among the passivating materials, superphosphate considerably reduced the contents of the exchangeable Cu, Pb, Cd and Zn, and the relevant passivating effects were 58.61%, 46.95%, 46.20% and 19.23%, respectively. However, adding superphosphate scarcely mobilized As (0.90%) compared with other passivating treatments (8.41-19.64%). This study suggests that adding superphosphate could have many positive effects on heavy metal passivation in multimetal cocontaminated waste composting.