Management of mineral processing tailings and metallurgical slags of the Congolese copperbelt: Environmental stakes and perspectives

Abstract

Abstract Mining activities lead to substantial quantities of tailings and slags containing metallic trace elements (MTE), leave persistent pollutants in the environment and are toxic even in low concentrations. Concerning the Congolese copperbelt, more than 416 million tons of mineral tailings and metallurgical slags were inventoried, most of which are not environmentally friendly. These are regarded as a critical environmental hazard for the surrounding population as they are stored in dams built between valleys of rivers, without protection. In order to gain insight into the nature of wastes from copper ores processed in DR Congo, and to suggest adequate waste management strategies, samples from selected sites were chemically analysed and subjected to various leaching tests. Results obtained in this study revealed that, though potentially recoverable, the investigated mine wastes are leachable and can be hazardous for the environment. In a normal leaching scenario using neutral water, these wastes exhibited leached amounts (also known as release) as high as 0.5%, 3% and even 30% for pyrometallurgical slags, flotation and hydrometallurgical wastes, respectively. The Toxicity Characteristic Leaching Procedure (TCLP) demonstrated that pyrometallurgical slags are as leachable as flotation and hydrometallurgical wastes, with more than 30% release. This confirms serious risk to the environment. As Congolese legislation considers these wastes as artificial ore bodies that can be subjected to a separate exploitation permit, processing plant owners neglect to get rid of them. To process the Congolese copperbelt ore bodies in a sustainable development context, the production unit operators should, through appropriate studies, classify their wastes and institute a management plan which takes into account the need for environmental protection. One such plan considers the use of geomembranes to prevent infiltration. In the perspective of mining regulation revision, the responsibility of processing plant owners will be linked to damage of the environment in accordance with the principle of ‘the polluter pays’.