Advanced membrane-based operations for recovery of minerals from desalination brines and exhaust batteries leachate

Abstract

The need to implement innovative technological approaches to secure undistorted access to raw materials and minerals is due to EU high dependance on import of several metal ores from international market and to problematic politic relationship with governance of countries where minerals extraction takes place, in conjunction with excessively high import reliance. In this scenario, the recovery of valuable metals and minerals (M&M) for commercial purposes from seawater desalination brines represents a promising potential path which has been raising interest over the past few years, considering that seawater is composed by 3.3% of dissolved salts and it is considered an invaluable source of minerals. In addition, this strategy represents an innovative approach from an environmental point of view, promoting the valorization of brines, that today are considered wastes and are rejected back to seas and oceans with an enormous impact on flora and fauna. In this thesis work, Membrane Distillation technology has been employed in combination to carbonbased photothermal nanomaterials as performance enhancers for minerals recovery from seawater brines and, moreover, in Air-gap configuration for the treatment of real groundwaters collected from former iron mines near Stockholm. On the other hand, this work is also aimed to point a steering direction for further developments in Donnan Dialysis process for the selective extraction of Magnesium from concentrated brine with the employment of commercial Cation Exchange Membranes. Moreover, a systematic investigation of ion exchange membrane selectivity towards different competing ions in brine treatment has been performed in combination to a Matlab process simulation, highlighting a thrilling match between simulation and real Dialysis process. In addition, Membrane Distillation technology has been included in an integrated system consisting in precipitation and distillation steps, aimed to solve complex separation problems connected to battery recycling and recovery of strategically important elements from battery leachate. During this last task, Lithium was successfully extracted from acid leachate with remarkable recovery percentages combined to a water recovery above 65%, obtained thanks to the concentration stage performed through Air-gap Membrane Distillation.