Analysis of the hazardous characteristics of water-quenched slag from smelting of wasted printed circuit board in oxygen-enriched side-blown furnace

Waste printed circuit boards (WPCBs) are classified as hazardous waste in China. Oxygen-enriched side-blown furnace (OESBF) smelting is widely used for their disposal and generates large quantities of slag. However, the environmental risk and hazardous classification of this slag remain unclear, restricting its safe disposal and resource utilization. In this study, systematic hazard identification was performed on industrial OESBF water-quenched slag, covering physicochemical properties, organic residues, corrosivity, acute toxicity, reactivity, leaching toxicity, and toxic substance content. The slag is a glassy solid dominated by calcium iron silicate and calcium magnesium silicate phases, with no organic pollutants detected. It is non-corrosive, non-acutely toxic, and non-reactive. The heavy metal leaching toxicity meets standard limits, and highly toxic elements were undetected. The cumulative toxicity remained within regulatory requirements. Heavy metals are considered to be stabilized through incorporation into silicate lattice and physical encapsulation in the glassy matrix. Theses results indicate that the OESBF water-quenched slag has no hazardous characteristics and can be classified as general industrial solid waste, supporting its safe disposal and resource utilization.