Results Of Precipitation Experiments Research Articles

Effective recovery of rare earth from (bio)leaching solution through precipitation of rare earth-citrate complex

Bioleaching is considered an alternative to traditional rare earth extraction technology. However, since rare earth elements exist as complexes in bioleaching lixivium, they cannot be directly precipitated by normal precipitants, which restricts their further development. This structurally stable complex is also a common challenge in various types of industrial wastewater treatment. In this work, a new method called a three-step precipitation process is first proposed to efficiently recover rare earth-citrate (RE-Cit) complexes from (bio)leaching lixivium. It consists of coordinate bond activation (carboxylation by pH adjustment), structure transformation (Ca2+ addition) and carbonate precipitation (soluble CO32- addition). The optimization conditions are determined to adjust the lixivium pH to around 2.0, then add calcium carbonate until the n(Ca2+): n(Cit3-) is more than 1.4:1 and lastly add sodium carbonate until n(CO32-): n(RE3+) is more than 4:1. The results of precipitation experiments using imitated lixivium show that the rare earth yield is more than 96% and the impurity aluminum yield is less than 20%. Subsequently, pilot tests (1000 L) using real lixivium were successfully conducted. The precipitation mechanism is briefly discussed and proposed by thermogravimetric analysis, Fourier infrared spectroscopy, Raman spectroscopy and UV spectroscopy. This technology is promising in the industrial application of rare earth (bio)hydrometallurgy and wastewater treatment due to its advantages of high efficiency, low cost, environmental friendliness and simple operation.

Hydrochemische Ergebnisse zur Aufbereitung stark belasteter Oberflächenwässer und Uferfiltrate mit Kalkhydrat. Teil 2

Continuing the first part on this subject, the results of precipitation experiments are described by the example of the removal of humic acid and lignosulphonic acid. Moreover, to increase the number of process variants and in accordance with process methods after Haberer, there is proposed a two‐stage chemical treatment, inter alia. According to the latest findings, already at the first stage a metallic salt dosing should be done, so that the purification effect can be improved. This new technique, termed “combination stage flocculation”, is based on new findings concerning the solubility behaviour of aluminium compounds at higher pH‐values in the presence of magnesium salts, when slightly soluble aluminium‐magnesium double hydroxides originate.