Abstract
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.
Highlights
Red mud is an industrial residue generated during the Bayer process of alumina production (Jones and Haynes 2011)
About 140 million tons of bauxite residue are generated every year, which are normally placed in huge tailing ponds in contact with the atmosphere or discharged into the sea, often in a noncontrolled manner (Evans 2016; Power et al 2011; Borra et al 2015)
Water content in the red mud sample obtained by dehydration method and by lyophilisation was 31.5 ± 0.5 wt% and 31.0 ± 0.5 wt%, respectively
Summary
Red mud is an industrial residue generated during the Bayer process of alumina production (Jones and Haynes 2011). For each ton of alumina, approximately 1–1.5 metric tons of red mud are produced (Kumar et al 2006). About 140 million tons of bauxite residue are generated every year, which are normally placed in huge tailing ponds in contact with the atmosphere or discharged into the sea, often in a noncontrolled manner (Evans 2016; Power et al 2011; Borra et al 2015). The median particle size of red mud is normally in the range of 5–10 μm; the breadth of particles.
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