Leaching Process of Weathered Crust Elution-Deposited Rare Earth Ore With Formate Salts

Abstract

To strengthen the rare earth leaching process and weaken the hydration of clay minerals for preventing landslides, it is of great importance to adopt a green and sustainable leaching agent in the industry. In this work, the leaching process of weathered crust elution-deposited rare earth ores with formate salts (ammonium formate, potassium formate, and sodium formate) was investigated. The effects of formate salts on the linear swelling ratio and zeta potential of the clay minerals were studied. The experimental results showed that ammonium formate could effectively recover the rare earth elements from weathered crust elution-deposited rare earth as well as inhibit the leaching of impurity aluminum. At room temperature, when the ammonium formate concentration was 1% wt, the leaching efficiencies of rare earth and aluminum were 87 and 37%, respectively. Compared with traditional inorganic ammonium salts, the inhibition effect of impurity aluminum was obvious. In addition, the results of the linear swelling ratio in the clay minerals showed that the inhibit ability of formate salts on the hydration of clay minerals enhanced with the increase of the formate concentration, and the order of the inhabitation on the clay minerals followed: 1% ammonium formate > 1.5% potassium formate > 2.5% sodium formate > distilled water. Based on the double layer theory, ammonium formate and potassium formate could effectively compress clay mineral particles to avoid water intake, which could increase the interaction between clay mineral particles and greatly reduce the electronegative property of the clay minerals, so as to effectively reduce the surface hydration of clay minerals to decrease the swelling of rare earth ore. The results of this experiment have important and practical significance in guiding the prevention of landslides, promoting the in-situ leaching technology, and effectively protecting the ecological environment in mining areas.

Effects of Ion Characteristics on the Leaching of Weathered Crust Elution-Deposited Rare Earth Ore

“…The leaching agent was added at the ratio of 2:1 for liquid/solid. The leaching agent was added into the glass column under the control of precision pump at a speed of 0.5 mL/min (Chen et al, 2018b). The self-made leaching device was shown in Figure 2.…”

“…Zhang et al (2013) and He et al (2016) found that the order of the leaching efficiency of rare earth by inorganic ammonium salt was (NH 4 ) 2 SO 4 < NH 4 Cl < NH 4 NO 3 , which was related to the complexation capacity between rare earth ions and anions. Chen et al (2018a) and found that the order of mass transfer efficiency of rare earth under three magnesium salts was Mg(NO 3 ) 2 > Mg(Cl) 2 > MgSO 4 in the study of mass transfer process of weathered crust elutiondeposited rare earth ores by magnesium salts. The inhibiting swelling effect was highest with magnesium nitrate as the leaching agent, and the mass transfer efficiency of rare earth was related to the type of anion.…”

Application of chromatographic plate theory on the weathered crust elution-deposited rare earth ore with carboxylate

“…The thermal motion of ion speed would be raised because of the leaching temperature increasing. In addition, the solution diffusivity and ions exchangeability would be improved (Aydogan, 2006).Elevating leaching temperature was conducive to the exchange reaction between ammonium ions and rare earth ions when ammonium tartrate and ammonium citrate were used as lixiviant (Chen, 2018). In order to analyze the effects of the leaching temperature on the mass transfer of the rare earth and aluminum, the HETPs of rare earth and aluminum at different temperature were calculated and shown in Fig.…”

“…Moreover, Chen et al found the optimum condition for rare earth and aluminium were 0.4 mL/min of flow rate and 0.2 mol/L of magnesium ion concentration. Under this condition, the mass transfer efficiency of rare earth and aluminium with three kinds of magnesium salts follow the order of Mg(NO3)2 > MgCl2 > MgSO4 (Chen, 2018). Li et al found that the 3 g/L ammonium citrate could promote the exchange of rare earth ion, improve the rare earth recovery, reduce the amount of ammonium salt, and reduce the pollution of ammonia nitrogen pollution .…”

Chelation-Assisted Ion-Exchange Leaching of Rare Earths from Clay Minerals

“…Wang et al [43] investigated various carboxylic acids as additives to 0.3 mol/L NH 4 Cl for the leaching of REEs from ion-adsorption ores, while Zhang et al [44] explored the leaching of rare earth from ion-adsorption ores by ammonium acetate. More recent studies involving the use of chelating/complexing reagents during ion-exchange leaching of rare earths were conducted by Chai et al [45], who explored ammonium carboxylate-ammonium citrate mixture as lixiviant, and Chen et al [46], who evaluated formate salts. Similarly, studies conducted by Cristiani et al made use of the good complex-forming capacity of polyamines to evaluate the efficiency of functionalized clays as sorbents capable of the uptake/removal of heavy metals from polluted aqueous effluents [47] and lanthanides from leachates of electronic wastes [48].…”