Characteristics and factors that influence heavy metal leaching from spent catalysts

With the extensive use of nonferrous metals and metal catalysts, solid wastes containing heavy metals release metal ions into soil and surface water through erosion and leaching. This is one of the major threats to the global environment and human health. Studying the characteristics and impact factors of heavy metal leaching from solid waste is a critical part of managing spent catalysts and environmental risk. In this work, the characteristics of and factors that influence leaching and seepage release from typical spent catalysts and lead-zinc smelting slag were studied. The results indicated that metal ions leached more easily in an acidic environment (pH 4.5) and an environment with DOM than in a neutral environment (pH 7.0). Metal ion leaching was favored by a liquid-to-solid ratio of 20:1. The concentrations of metal ions released from the spent catalysts in sequential leaching experiments were higher than those in column leaching experiments. Leaching of metal ions in the presence of different leaching agents and from different spent catalysts can be described by different controlling models of the shrinking core model, but changes in the liquid-to-solid ratio showed no obvious correlation with changes in the metal release mechanism. These results provide important information for spent catalyst management and risk prevention and control.