Bauxite residue sinter leach process – phases formation, reaction pathways and kinetics

Abstract

Reactive silica in bauxite is a key challenge for the alumina industry due to the associated losses of sodium hydroxide and alumina associated with processing this impurity. The bauxite residue sinter leach process (BRSLP) is a potential method of recovering sodium hydroxide and alumina from bauxite residue. In this research, bauxite residue lime sinters were characterised using a combination of quantitative X-ray diffraction in conjunction with scanning electron microscopy as well as for leaching performance. It is shown that sintering reactions proceed at a significantly faster rate than previously reported which has a positive implication for industrial application. A new set of reactions and reaction pathways are proposed which describe bauxite residue lime sintering in greater detail than previously possible.

Extraction of Valuable Elements from Red Mud with a Focus on Using Liquid Media—A Review

“…Hodge et al [42] studied the kinetics of sodium monoaluminate formation in the process of red mud sintering with soda and calcium carbonate at 1000 • C. Peak formation of sodium monoaluminate occurred after 5 min of sintering, and then its content in the sample decreased with an increase in sintering time. Leaching of the obtained sinter by a solution containing 5 g/L NaOH and 5 g/L Na 2 CO 3 at 80 • C for 30 min dissolved 64% of sodium and 55% of aluminum.…”

Recovery of Iron and Aluminum from Bauxite Residue by Carbothermic Reduction and Slag Leaching

“…Moreover, a less leachable calcium aluminate phase may also affect the leachability of others. Al can also be immobilized in gehlenite (C2AS; Ca 2 Al 2 SiO 7 ) and the content of silica in the bauxite residue poses a great challenge for Al recovery [17]. The addition of CaO can be used for capture of SiO 2 in a calcium silicate (C2S; Ca 2 SiO 4 ) phase and may have a positive effect on the Al recovery [18,19].…”

Extração de escândio a partir de reservas não exploradas utilizando rota hidrometalúrgica com foco no desenvolvimento sustentável.

“…The authors showed that 95% of sodium was removed [154]. A similar achievement was obtained using different approaches where the sodium could be recycled to the bayer process in its alkaline form, NaOH [155].…”

“…In the Bayer Process, silica reacts forming sodium aluminum hydrosilicate and is removed from the Bayer liquor as part of red mud. Several studies and patents have discussed processes to remove reactive silica from the bauxite and to recover aluminum and sodium from red mud [155,[306][307][308].…”

“…The red mud from Greece was mixed with graphite powder and wollastonite and heated at 1500 o C. Results showed that 85% of iron was removed, and the REE content increased in slag comparing with concentration in red mud. Leaching experiments in slag showed that all scandium, 70% of titanium and most of REE were recovered using HCl and HNO3 at 90 o C[274] Hodge et al (2019). studied the recovery of aluminum and sodium by the bauxite residue sinter leach process (BRSLP).…”