Crust Elution-deposited Rare Earth Ore Research Articles

Development of pore structure characteristics of a weathered crust elution-deposited rare earth ore during leaching with different valence cations

To explore the evolution of characteristics of pore structure of a weathered crust elution-deposited rare earth orebody during the leaching process with different valence cations, leaching solutions with NH4+, Mg2+, Al3+ as cations were prepared to carry out simulated column leaching experiments. Nuclear magnetic resonance (NMR), scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) were used to measure the microscopic characteristics of samples, then the and mechanisms of pore structure evolution of samples during leaching with different valence cations were analyzed. The results showed that: in the main reaction stage, ion displacement reaction in three different leaching solutions resulted in the top-down migration of solid fine particles; then the continuous evolution of secondary pore structure occurred, and then the drainage characteristics of leaching solution were affected. The evolution of pore structure of rare earth orebody induced by leaching solution with different valence cations was generally similar: the pore structure of the orebody firstly evolved from large pores to small pores; whereas at the end of ion exchange, the pore structure evolved from small pores to larger pores. However, there were significant differences in the pore proportion of different sizes. The number of large pores and extra-large pores in the samples of the ammonium sulfate leaching group was the largest, followed by the magnesium sulfate leaching group, and the least were found in the aluminum sulfate leaching group. The mechanism study showed that this difference was caused by the dynamic transformation (deposition and release) of fine particles of rare earth ore on the pore surface, which was affected by the change of ionic strength, the valence cation and the pH value of leaching solution caused by ion substitution.

Effect of potassium chloride on leaching process of residual ammonium from weathered crust elution-deposited rare earth ore tailings

Ammonium sulfate has been widely applied as a leaching agent to leach rare earth from weathered crust elution-deposited rare earth ore because of its higher selectivity. However, large amount of ammonium remained on the ore body after the completion of rare earth leaching, and it was necessary to leach it from the ore body from the environmental point of view. In this work, potassium chloride was used as a leaching agent and effects of potassium chloride concentration, leaching agent pH, liquid/solid ratio and flow rate on the leaching process of ammonium were investigated in detail. It was found that potassium chloride could effectively leach the residual ammonium from rare earth tailings, and the leaching efficiency and leaching rate of residual ammonium were significantly higher than that with deionized water. Leaching agent pH almost had no effects on the leaching process of residual ammonium in the range of 2–6, and a greater impact on it at pH 8. The flow rate could effectively enhance the leaching efficiency. The optimum conditions of leaching residual ammonium were 0.06 mol/L of potassium chloride, pH 5.5–6.5 of leaching agent, 2:1 of liquid/solid ratio and 0.6 mL/min of flow rate. At these conditions, the leaching efficiency of residual ammonium was 95.78%, and the concentration of ammonium in the leachate at the final stage was 0.89 mg/L, which could meet the requirements for environment. The leaching process of ammonium in rare earth ore tailings was controlled by the inner particle diffusing according to the kinetic analysis. The reaction order was 0.117. These results suggest a promising route for the environmental remediation of weathered crust elution-deposited rare earth ore after in-situ leaching.

Adsorption and desorption performances of ammonium on the weathered crust elution-deposited rare earth ore

Release of the remaining ammonium salts from the weathered crust elution-deposited rare earth ore (WCE-DREO) would pose a serious threat to the environment. Thus, in this study, the adsorption and desorption performances of the WCE-DREO and four minerals that composed it were investigated to select an efficient eluent for the remained ammonium removal. Results showed that the ammonium ion adsorbed on the WCE-DREO and the clay minerals as a monolayer, and the calculated adsorption capacities were as follows: montmorillonite > WCE-DREO > halloysite > illite > kaolinite due to their different structure. pH experiment showed that it had great effects on ammonium adsorption on both the WCE-DREO and the investigated clays. Kinetic experiments showed that ammonium sorption and desorption process were both a fast process. Co-ions experiments showed that Mg2+ showed the highest inhibition effect on the ammonium adsorption on the WCE-DREO due to its ionic character. Based on this data, magnesium salt was chosen as the eluent, and results showed that more than 93 % of the remaining ammonium ion could be removed from the WCE-DREO in the batch and column experiments.

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

To reveal the ion-exchange mechanism in the leaching process of weathered crust elution-deposited rare earth ores with different leaching agents, the effects of a variety of cations and anions at different concentrations on the leaching process were investigated, including Al3+, Fe3+, Ca2+, Mg2+, Na+, K+, and Cl−, , and . Meanwhile, the relationships between different concentrations of cations and anions and leaching efficiency were investigated, as was the relationship between different concentrations of cations and anions and zeta potential. The effect of different ions on the swelling of clay minerals during leaching process was also investigated. The results shown that was the most affected electrolyte cation in terms of rare earth leaching efficiency during the leaching process of weathered crust elution-deposited rare earth ore among three different cationic valence states, and the leaching efficiency was 86.93% at the optimal leaching concentration. The influence of the three anions on the leaching efficiency of rare earth was , and the leaching efficiency of rare earth were 83.21, 81.52, and 80.12% at the optimal leaching concentration, respectively. The had the greatest effect on the zeta potential of weathered crust elution-deposited rare earth ore, and the zeta potential was −18.1 mV at the optimal leaching concentration. Additionally, the order of the effect of three anions on zeta potential was . Combined with the effect on the rare earth leaching process, anions and cations were considered separately, and and Cl− were selected; the relationship between the rare earth leaching efficiency and zeta potential conforms to the follow equations: :Y = −0.48X2 – 13.51X – 1.58, R2 = 0.98133 and Cl−:Y= −1.22X2 – 17.64X + 23.29, R2 = 0.99010. It was also found in the swelling experiment of the weathered crust elution-deposited rare earth ore that the swelling ratio of clay minerals was the lowest when the cation and anion were and Cl− and the swelling ratios were 1.874 and 2.015%, respectively.

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

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.

Preparation of crystalline rare earth carbonates with large particle size from the lixivium of weathered crust elution-deposited rare earth ores

Crystalline rare-earth (RE) carbonates having large particle size were prepared from the lixivium of weathered crust elution-deposited rare-earth ores using the precipitation method with ammonium bicarbonate as the precipitant. Their chemical composition was studied using elemental and thermogravimetric analyses (TGA), and their structure and morphology were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results demonstrate that the crystalline rare-earth carbonate is a hydrated basic carbonate or oxycarbonate and not astable intermediate carbonate in the process of thermal decomposition. The particle size of crystalline rare-earth carbonates with large particle size is in the range of 50–200 µm. With an RE2O3 content of up to 95wt%, the quality of crystalline rare-earth carbonates is higher compared to the Chinese National Standard (GB/T 28882-2012). The quality of the product is superior to the Chinese National Standard.

Ammonia nitrogen sources and pollution along soil profiles in an in-situ leaching rare earth ore

The ammonium sulphate ((NH4)2SO4) in-situ leaching process is the most widely used extraction technology for weathered crust elution-deposited rare earth ores (WCED-REOs). Highly concentrated (NH4)2SO4, a representative leaching agent, is often used in the leaching process of WCED-REOs. However, this in-situ leaching process causes nitrogen pollution in the soil, surrounding surface and ground water due to the high concentrations of (NH4)2SO4 solutions used as a long term leaching agent. To date, the mechanism behind the variations in ammonia nitrogen (AN) in deep soil profiles is unclear. We conducted vertical and lateral soil sampling and analyzed the collected samples for soil moisture, pH, ammonia forms, and AN contents in soil profiles deeper than 500 cm in an in-situ leaching mining area of Ganzhou, Jiangxi Province, southern China. The results show that primary chemical pollutants in the soil are derived from residual leaching agents with high acidities and concentrations of AN. Twelve years after the mining process was completed, the mean pH values of the tailings in the mining area were 3.90 and 4.87 in its lower reaches. Due to the presence of chemical residues, the AN concentration was 12–40 times higher than that of the raw ore soil before it was mined. The percentages of different ammonium forms in the rare earth tailing soil were 65%, 30%, and 5% for the water-soluble, exchangeable, and fixed ammonium forms, respectively. The results of this study support effective prevention and remediation treatment of environmental problems caused by AN pollution of the soil in WCED-REOs.

Leaching Kinetics of Weathered Crust Elution-Deposited Rare Earth Ore with Compound Ammonium Carboxylate

Due to the special properties of the ammonium salts, ammonium acetate and ammonium citrate were used to explore the best leaching conditions of rare earth with compound ammonium carboxylate. This paper explored the influence of the molar ratio, ammonium concentration, experimental temperature, and pH of the compound leaching agents on the leaching efficiency of rare earth and aluminum, and it analyzed the leaching process based on the leaching kinetics, which provides a new method for leaching rare earth from the weathered crust elution-deposited rare earth ore. The results showed that under the conditions where the molar ratio of ammonium acetate and ammonium citrate was 7:3 and the ammonium concentration was 0.15 mol/L, the leaching efficiency of rare earth was the highest when the pH of leaching agent was 4.0 and the experimental temperature was 313 K. Meanwhile, when CH3COONH4 and (NH4)3Cit were used to leach rare earth ore, the leaching reaction kinetics equation of rare earth and aluminum were obtained. In the temperature range of 283–323 K, the apparent activation energy of rare earth was 14.89 kJ/mol and that of aluminum was 19.17 kJ/mol. The reaction order of rare earth was 0.98 and that of aluminum was 0.79. The results were in accordance with the shrinking core model and indicate that the concentration of the leaching agent had a greater influence on rare earth than aluminum. This process can reduce the use of ammonium salt, and it is of great significance to extract rare earth elements from weathered crust elution-deposited rare earth ore and improve the utilization rate of resources.

Effect of particle size and grain composition on two-dimensional infiltration process of weathered crust elution-deposited rare earth ores

Abstract The two-dimensional infiltration experiment was carried out by means of digital image technology. The evolution process of the wetting body was described. The wetted front distance and the time show a very significant power function relationship. The horizontal wetted distance is larger than the vertical wetted distance in the initial stage. Then, the vertical distance of the wetted body gradually approaches to the horizontal distance. The infiltration distance decreases as the content of fine particles increases. The wetted front migration rate curve shows a three-stage change law, and it increases with the increase of coarse particle content. The directional velocity ratio is defined. The initial value of horizontal infiltration rate is larger than that of vertical one, and then the vertical infiltration rate is gradually close to the horizontal value. The empirical relationship between the characteristic particle size and the stable infiltration rate is established, which provides a theoretical basis for the prediction of the stable infiltration rate in in-situ leaching.

Swelling of clay minerals during the leaching process of weathered crust elution-deposited rare earth ores by magnesium salts

To ensure the safety of leaching process in the weathered crust elution-deposited rare earth ore, it is of great importance to decrease the swelling of clay minerals in the rare earth ore for preventing landslides and other hazards. Meanwhile, it is also necessary to ensure the leaching efficiency of rare earth ores during industrial production. In this study, the effect of the magnesium ion concentrations and acidity of magnesium salts on the swelling process was investigated. The inhibiting properties of the optimized magnesium salts were evaluated by anti-swelling experiments. The results show that the relation between the linear swelling ratio of the clay minerals and time correspond with the equation δ = A·e-B/t when the rare earth minerals were recovered from weathered crust elution-deposited rare earth ore with magnesium salts. The optimal leaching conditions were determined to be 0.2 mol/L of magnesium nitrate with a pH below 6.0, with the kinetic equation: δ = 1.5995·e-5.5170/t. According to the evaluations, magnesium nitrate shows a strong capacity to inhibit the hydration swelling and dispersion of clay minerals at room temperature; the anti-swelling rate of 0.2 mol/L magnesium nitrate was 65%, the highest among the magnesium salts. Decreasing the pH and leaching temperature of the magnesium salt solution could effectively reduce the swelling of clay minerals during leaching. The results of the experiment could lead to an improvement in the in-situ leaching technology and reduce the risk of hazards, which has a significant meaning in the safe operations of the mining process.

Non-ammonia enrichment of rare earth elements from rare earth leaching liquor in a magnesium salt system I: Precipitation by calcium oxide

Combining the environmental advantage of magnesium salt compound leaching agent, calcium oxide was used as a precipitant to enrich rare earth elements from rare earth leaching liquor in a magnesium salt system. The use of magnesium salt compound leaching agent and calcium oxide precipitant can achieve the effective circulation of Ca and Mg, and finally solve the ammonia-nitrogen pollution problem in the whole extraction process of the weathered crust elution-deposited rare earth ore. The study suggested that alkaline rare earth sulfates and rare earth hydroxides could generate in the precipitation process, which was proved by the Hazen model calculation and the calcium oxide addition experiments. What's more, it was showed that, under the optimum precipitation conditions, the precipitation efficiency of rare earth was 99.72% and the purity of rare earth concentrate is 82.21%, and the SO3 content in the rare earth concentrate was as high as 13.44% because of the formation of alkaline rare earth sulfates during the precipitation process. In order to reduce the SO3 content, the stirring washing of the precipitation enrichment with an sulfate removal agent was proposed in this paper. The anion of the sulfate removal agent could compete with sulfate ions in the stirring washing process. As a result, sodium hydroxide could be the first choice for further detailed study. When the precipitation enrichment was washed with sodium hydroxide, the purity of the rare earth concentrate was 88.03% and the SO3 content was 7.51% respectively. Hence, a feasible operation would be provided for the non-ammonia enrichment of rare earth from leaching liquor in a magnesium salt system. The research in this paper could have great significance for environmentally-friendly extraction of the weathered crust elution-deposited rare earth ore and the improvement of resource utilization.

Research progress on leaching technology and theory of weathered crust elution-deposited rare earth ore

Rare earth (RE) with specific application value has become the relatively important strategic resource for all countries. Weathered crust elution-deposited rare earth ore (WCED-REO) are rich in middle-heavy RE, and its exploitation restrict the global supply of the middle-heavy RE. The leaching technology directly determines the leaching efficiency of RE in WCED-REO. The selection and use of the leaching agents are the most important parts of the leaching technology. The leaching mechanism is at the core of the leaching technology and also affects the effective utilization of the leaching agents. The research and development of leaching technologies, leaching agents, and leaching mechanisms of WCED-REO are discussed in this article. The development processes of exiting leaching technologies are introduced. The advantages and disadvantages of barrel leaching, pool leaching, heap leaching, in-situ leaching, and other leaching technologies are compared. And the new and practical leaching technologies are put forward. The research progresses of ammonium salt leaching agents, composite ammonium salt leaching agents, and novel non-ammonium leaching agents in recent years are reviewed. The leaching effects of different leaching agents are compared comprehensively to provide guidance for industrial application and research direction of the best leaching agent in the later period. The leaching basic theory, as well as the mass transfer process and leaching kinetics of rare earth are introduced. The mass transfer processes in leaching mechanism are explained from the macroscopic and microscopic perspectives. The further research directions of the leaching technologies, leaching agents, and leaching mechanism of WCED-REO are put forward, which provide the theoretical guidance and technical supports for the green and efficient exploitation of WCED-REO.

Seepage mechanism during in-situ leaching process of weathered crust elution-deposited rare earth ores with magnesium salt

Seepage mechanism during in-situ leaching process of weathered crust elution-deposited rare earth ores with magnesium salt

Study on Pb release by several new lixiviants in weathered crust elution-deposited rare earth ore leaching process: Behavior and mechanism.

New leaching agents could lead to a reduction in ammonia nitrogen pollution and the supplementation of soil nutrients during in-situ mining. They could also result in the release of even more toxic heavy metals, which has an impact on the environment as well as human health. In this study, column leaching experiments were used to simulate in-situ leaching, and the leaching behavior and fractional changes of lead in weathered crust elution-deposited rare earth ore by different leaching agents were studied. The experimental results showed that the amount of lead that was leached followed the order of CLA (60% CaCl2+25% NH4Cl+15% MgSO4)>(NH4)2SO4>MgSO4. The lead leaching process was comprised of both an acceleration and deceleration stage that followed the first order kinetic model. The amount of Pb when using compound agent was the greatest most likely because of the presence of Cl-. The soil heavy metal morphology test showed that the three leaching agents primarily leached acid extractable lead, and the compound leaching agent leached the greatest amount of acid extractable Pb, which mainly due to the presence of NH4Cl. The reducible fraction was enriched in the direction of migration of the leachate, which was due to the presence of SO42-. These results indicate that the introduction of leaching agents during the mining process pose a greater risk for the release of heavy metals and provide a theoretical basis for the prevention and remediation of heavy metal pollution in mining areas where new leaching agents were used.

Preparation of Modified Montmorillonite and Its Application to Rare Earth Adsorption

Montmorillonite, the major clay mineral in the tailings of weathered crust elution-deposited rare earth ores, was modified as an excellent adsorbent to enrich rare earth ions from solutions. It was demonstrated that 5% H2SO4 could be used as a modifier to effectively enhance the adsorption capacity of montmorillonite after modifying for 3 h with a liquid:solid ratio of 40:1 at 90 °C. A superior modified montmorillonite over montmorillonite on adsorption performance was analyzed by the XRD, FT-IR, SEM, and BET (Specific Surface Area and Pore Diameter Analysis). The adsorption behaviors of La3+ and Y3+ on modified montmorillonite were fitted well with the Langmuir isotherm model and their saturated adsorption capacities were 0.178 mmol/g to La3+ and 0.182 mmol/g to Y3+, respectively. Furthermore, (NH4)2SO4 as a common leaching agent in weathered crust elution-deposited rare earth ores, were successfully used as the eluent to recover the adsorbed rare earth ions.

Seepage process on weathered crust elution-deposited rare earth ores with ammonium carboxylate solution

Seepage process on weathered crust elution-deposited rare earth ores with ammonium carboxylate solution

Leaching Process and Mechanism of Weathered Crust Elution-Deposited Rare Earth Ore

The leaching processes and mechanisms of weathered crust elution-deposited rare earth (RE) ores with ammonium sulfate were investigated for their high efficiency and low consumption exploitation. The leaching process is a typical reversible heterogeneous ion exchange reaction in liquid–solid systems. The raw ore and leached tailings were analyzed by SEM and FTIR. Results indicated that no dissolution or structural changes of the ores occurred during the leaching process. The migrations of RE3+, Al3+, and $$ {\mathrm{NH}}_4^{+} $$ in the leaching process were studied under various liquid–solid ratios. With increasing liquid–solid ratio, the content of $$ {\mathrm{NH}}_4^{+} $$ adsorbed on clay mineral by physical effect decreased, $$ {\mathrm{NH}}_4^{+} $$ adsorbed by ion-exchange increased, and the content of exchanged RE and Al increased until reaching equilibrium. The adsorption capacity of the RE ores for $$ {\mathrm{NH}}_4^{+} $$ remained about 0.61–0.63 mg/g. It was difficult to desorb $$ {\mathrm{NH}}_4^{+} $$ from RE ores with washing water alone. The leaching mechanism of Al was the same as RE, but the leaching of Al slightly lagged behind RE. At the optimal liquid–solid ratio of 0.4:1, the leaching efficiencies of RE and Al were 95.51% and 90.99%, respectively, and 56.65% of $$ {\mathrm{NH}}_4^{+} $$ remained in the leachate. After impurity removal and RE precipitation, the leachate can be reused by replenishing fresh leaching agent. The aim of this study is to enhance the leaching process of RE, restrain the leaching of impurities, and decrease the consumption of leaching agents.

Simulation of one-dimensional column leaching of weathered crust elution-deposited rare earth ore

The ion exchange model of the leaching process was determined via batch leaching experiments using the Kerr model, with the selectivity coefficient experimentally determined to be 12.59×10−10 L2/g2. Solute transport laws of ammonium ions (NH4+) and rare earth ions (RE3+) in column leaching were described by the convection−dispersion equation (CDE). The source and sink in the CDE were determined by the Kerr model. The CDE with strong nonlinearity was solved using the sequential non-iterative method. Compared with the breakthrough curve of RE3+, the correlation coefficient between the simulated and experimental curves reached 0.8724. Therefore, this method can simulate the one-dimensional column leaching of weathered crust elution-deposited rare earth ore. Moreover, the effects of different concentrations of ammonium sulfate ((NH4)2SO4) solution on the leaching rate of rare earth were analyzed. The optimal concentration of the (NH4)2SO4 solution had a linear relationship with the rare earth grade.

Lanthanum （Ⅲ） and Yttrium （Ⅲ） Adsorption on Montmorillonite: The Role of Aluminum Ion in Solution and Minerals

ABSTRACT Weathered crust elution-deposited rare earth ores (WREO) are the most important mineral sources of the middle and heavy rare earth in the world, which are rare earth ions (RE3+) adsorbed on clay minerals, such as montmorillonite, kaolinite, etc. In this work, the adsorption mechanism of Lanthanum ion (La3+) and Yttrium ion (Y3+) on montmorillonite was studied to clarify the interaction between RE3+ and clay minerals. The effect of aluminum ion (Al3+) on the adsorption behavior of La3+ and Y3+ was discussed, for the first time, to probe the role of Al3+ in aqueous solution and released from clay minerals. With the addition of Al3+ in solution, the adsorption capacity of RE3+ becomes much lower than that in the single RE3+ adsorption system, which indicates the inhibiting effect of Al3+ on the RE3+ adsorption. No distinct variation on the adsorption capacity of RE3+, and hence the more adsorbing sites occupied by Al3+ than RE3+ were observed at different molar concentration ratio of RE3+:Al3+ in rare earth (RE)–aluminum (Al) system. Nevertheless, there is a convert of Al3+ from adsorption to release at the molar concentration ratio from 1:5 to 1:2 of RE3+:Al3+ in RE–Al system due to the increasing initial concentration of Al3+. Kinetic studies display that the pseudo second-order kinetic model can best describe the RE3+adsorption and the Al3+release, and the two processes are controlled by chemical reaction.

Role of initial moisture content on the leaching process of weathered crust elution-deposited rare earth ores

Role of initial moisture content of ore was discussed to improve the leaching process of weathered crust elution-deposited rare earth ores, especially the difficult-to-permeate rare earth ores. Effects of the initial moisture content, the ammonium sulfate concentration and the liquid/solid ratio on the leaching efficiencies of rare earth and aluminum were investigated, and the leaching process under different initial moisture contents were further analyzed by the shrinking-core model and the chromatographic plate theory. The results showed that the ammonium sulfate concentration needs to be increased to 0.12 mol/L when the initial moisture content of ore is 20%, and a weak improvement on the leaching efficiency of rare earth can be investigated, where the leaching efficiency of rare earth is 95.35% and the aluminum is 94.75%, respectively. However, the leaching equilibrium time of rare earth and aluminum are significantly shorten from 853 min to 265 min for rare earth, and from 905 min to 350 min for aluminum, suggesting a great promotion of initial moisture content on the leaching rate of weathered crust elution-deposited rare earth ores. The leaching processes of weathered crust elution-deposited rare earth ores under different initial moisture contents are controlled by the inner particle diffusing according to the kinetic analysis. The reaction orders are 2.203 for rare earth and 1.980 for aluminum, respectively. The mass transfer discussion showed a smaller height equivalent to theoretical plate (HETP) corresponding to a higher initial moisture content indicating a better mass transfer of rare earth than aluminum. Therefore, the positive impact of initial moisture content of ore on the leaching process of weathered crust elution-deposited rare earth ores is confirmed by both the kinetic and the mass transfer discussions.