Uranium Extraction from Tailings by Dilute Alkali Pretreatment–Sulfuric Acid Leaching Technology

Preliminary extraction research was carried out to develop a suitable dilute alkali pretreatment–sulfuric acid leaching process for uranium recovery from tailings containing 80 ppm uranium. The effects of alkali concentration, liquid-to-solid ratio, stirring speed and leaching time on uranium content in the leaching residues were investigated. The results showed that the leaching efficiency of dilute alkali pretreatment–sulfuric acid leaching is superior to direct acid leaching. Only 13 ppm and 7.5 ppm of uranium remained in tailings by using NaOH and Na 2 CO 3 , respectively, with an alkali concentration of 10 g/L, a liquid-to-solid ratio of 20, and an agitation of 400 rpm for 2 h. In addition, uranium liberation was significantly promoted by forming pores during the leaching process. This technology has advantages of low energy consumption, high leaching efficiency and less impurity production compared to traditional direct acid leaching.