Beneficiation of acid mine drainage (AMD): A viable option for the synthesis of goethite, hematite, magnetite, and gypsum – Gearing towards a circular economy concept

Abstract

Pollution of water resources by acid mine drainage (AMD) has been an issue of primary concern in recent decades. This is rooted to the fact that AMD negatively affects the environment and its suitability to foster life. As such, efforts to recover, valorise and beneficiate minerals acquired from AMD treatment process have been ongoing, albeit with minimal success. With that in mind, this study unpacks novel ways of beneficiating AMD via the synthesis of valuable minerals with myriads of industrial applications. To this end, real AMD was used to synthesize goethite, hematite, magnetite, and gypsum (product minerals). Drinking water was also reclaimed as part of the treatment process, hence rendering this system a zero-liquid-discharge (ZLD) process. For the synthesis of goethite, hematite, and magnetite, Fe(III) and Fe(II) were recovered via sequential precipitation in batch reactors. Lime was added to treated water to synthesize high-grade gypsum. Furthermore, reverse osmosis (RO) was employed to reclaim drinking water as per South African drinking water standards (SANS 241) specifications. Product minerals were ascertained using advanced analytical techniques. Concisely, this study proved that AMD can be beneficiated into valuable minerals, which could be utilized in a number of industrial applications. The profits from selling the product minerals can potentially aid in offsetting the running costs of the treatment process, hence making this process self-sustainable. This will also foster the concept of circular economy and waste beneficiating, thus curtailing the impacts of AMD to different spheres of the environment.