Towards an integrated approach for red mud valorisation: a focus on titanium

In this work red mud, a highly alkaline waste product generated during alumina production process, was valorised as a source of valuable metals and as an adsorbent material. A hydrometallurgical process was developed in order to recover titanium from red mud. By a leaching step with hydrochloric acid followed by ammonia precipitation and a further purification step by solvent extraction with Cyanex 301 using toluene as a solvent, quantitative recovery of titanium with a high purity level (> 95%) was achieved. Red mud adsorption properties were also tested for metal removal from aqueous solutions. The results showed the red mud potential in applications such as environmental remediation. The adsorption order was found to be: iron > lead > copper > manganese, zinc. Red mud can be thus potentially valorised both as a source of secondary titanium and as an adsorbent material, according to the principles of Circular Economy which promote waste reduction and the preservation of natural resources.