A systematic approach to sulphidic waste rock and tailings management to minimise acid rock drainage formation

Abstract

One of the major environmental issues in the mining industry is that of Acid Rock Drainage (ARD), caused by the disposal of sulphide-bearing wastes. Re-examination of the manner in which waste materials are disposed from the mineral processing and extraction stages of metal recovery is required to relieve the environmental burden created and reduce the time frame of risk. In this study, the approaches to the removal of risk through removal of sulphur species were considered through a review of key work and a set of case studies addressing specific mineral wastes. Aspects of disposal of dump rock and tailings from mining operations processing mineral sulphides (especially pyrite) have been addressed, with the focus of reducing capacity to form ARD through removal of the sulphidic component of the waste. The understanding of the factors governing ARD generation from dump rock and tailings (similar to those governing mineral bioleaching) has been used to improve categorisation, separation and planned disposal of its components to mitigate ARD generation. While flotation and accelerated bioleaching have been used in the case studies to demonstrate sulphide removal by separation and reaction, a review of suitable unit operations is provided. Further, use of acid base accounting and net acid generation methods as static chemical methods for evaluating ARD potential is supported by the development of a biokinetic test for assessing ARD potential under an environment more cognisant with the ARD generating environment, as well as providing kinetic data over a shortened time frame to conventional kinetic tests. The biokinetic test also delivers solutions through which to analyse metal deportment through ARD. A case study using flotation for the physical separation of sulphide from tailings allowed the demonstration of the concept of risk removal.