Turning mine-tailing streams into sources of water and mineral salts in a membrane-sustained circular scenario

Abstract

The discharge of wastewater from the mining industry has a critical ecological impact, potentially endangering both soil and marine ecosystems. Alternatively, recovering pure water and valuable materials from these hypersaline streams through a technologically efficient process, would help reduce the ecological impact of the waste, while providing a viable supply chain for raw materials such as magnesium, potassium and others, considered critical to the economy. In this context, this work aimed to simultaneously recover pure water and mineral salts from mine wastewater by membrane-assisted crystallization (MAC). A prior theoretical study based on thermodynamic parameters attempted to predict salts precipitation at different temperatures. MAC tests were then performed at specific thermal gradients and feed pretreatment conditions, achieving preferential precipitation of solids products of different composition containing large quantities of Ca or Mg/K minerals from the real mine tailing wastewater. The experiments also demonstrated the central impact of heterogeneous nucleation effects.