Extraction of rubidium from respirable sintering dust

Respirable sintering dust was an abundant and hazardous waste arrested by electrostatic precipitators from iron and steel industry. In this study, this waste was first found to contain 0.3% Rb, existing in the form of chloride and making it a promising Rb extracting material. Meanwhile, 95.24% of Rb and 93.43% of K in it can be easily recovered by water leaching (S/L = 1:5), resulting in a solution of 740 mg/L Rb and 33.85 g/L K. Then this leachate was extracted with 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP) in sulphonated kerosene to separate Rb from K after purification. The optimized solvent extraction conditions were 1.0 mol/L t-BAMBP, phase ratio of 3:1, 1.2 mol/L alkalinity in aqueous. Moreover, the organic phase was treated with deionized water (O/A = 5:1) for scrubbing and 1.2 mol/L HCl (O/A = 5:1) for stripping. Under optimal conditions, a single Rb extraction and back-extraction efficiencies were 91.80% and 89.93%, respectively. Finally, a RbCl with 99.5% purity and a total Rb extraction rate of 58.26% were achieved by a multistage continuous countercurrent extraction. These results did not only indicate that respirable sintering dust is a new tremendous potential Rb source but also provide a promising way to utilize Rb from this dust.