Recovery of metal values from copper slag and reuse of residual secondary slag.

Resource and environmental factors have become major forces in mining and metallurgy sectors driving research for sustainability purposes. The concept of zero-waste processing has been gaining ground readily. The scant availability of high quality raw materials has forced the researchers to shift their focus to recycling while the exceedingly stringent environmental regulations have forced researchers to explore new frontiers of minimizing/eliminating waste generation. The present work is aimed at addressing both aspects by employing recycling to generate wealth from copper slag and producing utilizable materials at the same time thus restoring the ecosystem. Copper slag was characterized and processed. The pyro-metallurgical processing prospects to generate utilizable materials were arrived at through rigorous thermodynamic analysis. Carbothermal reduction at elevated temperature (near 1440°C) helped recover a majority of the metal values (e.g., Fe, Cu and Mo) into the iron-rich alloy product which can be a feed material for steel making. On the other hand, the non-metallic residue, the secondary slag, can be used in the glass and ceramic industries. Reduction time and temperature and carbon content were shown to be the most important process variables for the reaction which were optimized to identify the most favored operating regime that maximizes the metal recovery and simultaneously maximizes the hardness of the secondary slag and minimizes its density, the two major criteria for the secondary slag product to be utilizable. The flux addition level was shown to have relatively less impact on the process performance if these are maintained at an adequate level. The work established that the copper slag, a waste material, can be successfully processed to generate reusable products through pyrometallurgical processing.