Extraction of rubidium from kaolin clay waste: Process study

• Rubidium was extracted from kaolin clay wate by direct acid leaching and cholrination roasting followed by water leaching.
• Systematic study of the factors which will affect the rubidium extraction efficiency.
• The influencing mechanisms of various factors on extraction efficiency of rubidium recovery from kaolin clay waste were illuminated.
• Have found the best extraction process of rubidium from the kaolin clay waste.

Two ways, direct acid leaching and chlorination roasting–water leaching were used to leach rubidium from the kaolin clay waste in this work. The leaching behaviors of two methods were compared and the optimal extraction conditions were obtained. For direct acid leaching, maximum Rb extraction efficiency of the hydrochloric acid direct leaching is 30.6%. The extraction efficiency of sulfuric acid direct leaching is as high as 95.5%, whereas its subsequent processing is very unwieldiness and not suitable for practical application. For chlorination roasting–water leaching, the effects of mass ratio of kaolin clay waste with agents, roasting/leaching temperature, roasting/leaching time and the solid-to-liquid ratio, on the extraction efficiency were studied. The maximum Rb extraction 93.4% was obtained with a mass ratio of kaolin clay waste/CaCl2/NaCl of 1.0:0.3:0.2 at temperature 900 °C for time 30 min. Water leaching of the roasted mixture resulted in 90.6% Rb extraction under optimum conditions, viz. a solid-to-liquid ratio of 1:2, temperature 95 °C, time 60 min. In addition, the influencing mechanisms of various factors on extraction efficiencies were illuminated.

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