Crystallization of gibbsite from synthetic chromate leaching solution in sub-molten salt process

For the clean and economical production of chromium compounds, it is crucial to remove aluminates from chromate alkali solutions and utilize aluminum-containing compounds. In this work, carbonization was used to remove aluminates from a synthetic chromate leaching solution containing a high K2O/Al2O3 mole ratio. The influence of reaction temperature, carbonization time, flow rate of carbon dioxide, and seed ratio on the precipitation of Al was investigated. The optimal output was obtained under the following experimental conditions： a reaction temperature of 50 °C, a carbonization time of 100 min, a carbon dioxide flow rate of 0.1 L/min, and a seed ratio of 1.0. Gibbsite was obtained following carbonization. The structure and morphology of the gibbsite were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and laser particle size analyzer. The particle size distribution and morphology of the gibbsite were significantly influenced by the experimental conditions. The gibbsite had a mean particle size （d50） of 16.72μm. The thermal decomposition of the gibbsite was analyzed by XRD and the decomposition path was determined. The obtained coarseα-Al2O3 precipitate, which contains 0.08% Cr2O3 and 0.10% K2O, was suitable for subsequent utilization.

Separation and Concentration of Indium from Leaching Solution Containing Indium, Antimony and Iron Ions

Processing conditions of effectively separating indium from the leaching solution of a smelting antimony slag were studied. For the leaching solution containing indium and antimony and iron ions, indium was separated by extracting with HDEHP kerosine solution, washing antimony and iron ions with oxalic acid solution and stripping indium with a dilute solution of hydrochloric acid. InCl 3 solution with purity above 90% is obtained. Indium can be enriched through a circulation of stripping with a dilute HCl solution. The concentration of InCl 3 solution is about 25～30 g/L.

Enhanced extraction of scandium and inhibiting of iron from acid leaching solution of red mud by D2EHPA and sodium chloride

D2EHPA(P204),tri-butyl-phosphate(TBP)and sodium chloride(NaCl)were attractive for selective extraction of scandium from acid leaching solution of red mud.The extraction parameters of P204 concentration(X_(P204)),NaCl concentration(C_(NaCl)),pH value,reaction time,stirring speed and O/A were investigated to extract scandium and separate iron from the acid leaching solution.The extraction mechanism was analyzed by Fourier transform infrared spectroscopy(FT-IR)and thermodynamic theory.The single-stage extraction efficiency of scandium,iron andβ(Sc/Fe)were 99.1%,9.4%and 1061.2,respectively,with C_(NaCl) of 75 g/L and XP204 of 0.75 at solution pH value of 1.2 and stirring speed of 200 r/min for 6 min,in which a good separation effect of scandium and iron was obtained.The vibration absorption peak Sc─O was contributed to the extraction of scandium with P204.The complex[FeCln]^(3−n) existed in the solution with adding NaCl into the acid leaching solution.The value of n was higher and the valence state of the complex[FeCln]^(3−n) was lower with an increase of chloride concentration,which restricts the extraction efficiency of iron with P204.The extraction of three stages in the counter-current simulation experiments was carried out according to the McCabe-Thiele diagram.Gibbs free energy change(ΔG)of−5.93 kJ/mol,enthalpy change(ΔH)of 23.45 kJ/mol and entropy change(ΔH)of 98.54 J/(mol·K)were obtained in the solvent extraction proces,which indicate that the extraction reaction is easily spontaneous and endothermic and a proper increase of temperature is conducive to the extraction of scandium.

Deep Purification of Zinc Ammoniacal Leaching Solution by Cementation with Zinc Dust

Deep purification of zinc ammoniacal leaching solution by cementation using zinc dust was studied.The effects of relative amount of metallic impurities,dosage of zinc dust,purification time,temperature,pH value and total ammonia concentration in the solution on the purification of the solution were investigated.The results indicate that total ammonia concentration in the solution had no effect on the purification,but relative amount of metallic impurities,dosage of zinc dust,purification time,temperature and pH value of the solution were the main factors influencing the purification.Keeping appropriate molar ratio of copper to cadmium or nickel to cadmium was beneficial to the cementation of cadmium.Nevertheless,the presence of cobalt went against the cementation of cadmium and cobalt.All metallic impurities could be decreased to acceptable levels under the optimized conditions of 2 g/L of zinc dust dosage,1 h of purification time,35℃,pH value 9.03 of zinc ammoniacal leaching solution.The deeply purified zinc ammoniacal solution obtained by one-stage purification meets the requirements of zinc electrowinning.

Effect of the in situ leaching solution of ion-absorbed rare earth on the mechanical behavior of basement rock

A clear understanding of the evolution characteristics of leaching solution’s damage to the basement rock of ion-adsorbed rare earth deposits is essential in the in situ leaching mining.In this study,some laboratory tests were carried out to investigate the deterioration behavior and failure mechanism of rock under the erosion of leaching solution.For this purpose,granite specimens were soaked in the leaching solution for different periods and then some physical and mechanical parameters were measured.The experimental results show that the strength of the rock without any soaking is the maximum.After 60 d,the rock strength,mass(dry)and P-wave velocity(dry)decrease to the minimum,while the porosity of the specimens reaches the maximum.Moreover,the failure pattern of the specimens in the uniaxial compression tests is affected as the soaking time increases.The scanning electron microscopy(SEM)image results indicate that the erosion of quartz crystals inside the rock specimens gets more intense with the increase of soaking time.Also,the internal crystal failure mode gradually changes from the trans-granular to the inter-granular.The insights gained from this study are helpful for better understanding the evolution characteristics of leaching solution’s damage to the basement rock of ionadsorbed rare earth deposits.

Effects of Traditional Chinese Medicine Leaching Solutions on Rice Yield

[Objective] The aim was to explore the effects of different leaching solu- tions on yield increasing of rice. [Method] Three rice parents were chosen from dif- ferent areas to treat with leaching solutions and rice leaves were sprayed with leaching solutions in seedling stage and tillering stage, respectively. The test data were recorded. Horizontal and vertical researches were carried out on agronomic traits of rice in different varieties in test or control groups. [Result] The horizontal test showed that hybrid rice parents, submerged with traditional Chinese medicines increased significantly in rice yield and vertical research indicated that rice in control group decreased sharply in yield and in test group improved in both yield and quality, which was also true for following generations. [Conclusion] The test provides references for hybrid rice maintaining rice traits.

Direct extraction of Mo(VI) from acidic leach solution of molybdenite ore by ion exchange resin:Batch and column adsorption studies

The adsorption behavior of ion exchange resin D301 in the extraction of hexavalent molybdenum from high acidic leach solution was investigated. SEM, EDS and Raman spectra analyses were applied to studying the adsorption capacity, reaction kinetics and possible adsorption mechanism in detail. Results showed that the adsorption capacity of D301 resin for molybdenum from high acidic leach solution was up to 463.63 mg/g. Results of the kinetic analysis indicated that the adsorption process was controlled by the particle diffusion with the activation energy 25.47 k J/mol（0.9-1.2 mm） and 20.38 k J/mol（0.6-0.9 mm）. Furthermore, the molybdenum loaded on the resin could be eluted by using 2 mol/L ammonia hydroxide solution. Besides, dynamic continuous column experiments verified direct extraction of molybdenum from acidic leach solutions by ion exchange resin D301 and the upstream flow improved dynamic continuous absorption.

Scandium recovery from raffinate copper leach solution as potential new source with ion exchange method

Raffinate copper leach solution of the Iran Sarcheshmeh copper complex has up to 3 mg/L scandium(Sc),which is significantly better than many existing sources,making it a possible source for the recovery of Sc using the ion exchange method.Visual Minteq software was employed to ascertain the ionic species likely to be formed under operational conditions in the mine and for selecting the suitable ion exchange resin.The cationic resin thus chosen was employed statically with ions-bearing synthesized solutions and statically/dynamically for actual copper mining raffinate solution.Room temperature and pH of 1.5 showed the highest Sc adsorption.The dynamic tests established the full saturation of the resin at 450 BV of the raffinate solution flow.Using sodium carbonate for elution,desorption of Sc,Y and Ce from the resin during static elution tests at constant duration was higher than that of Fe,Al and Cu.The results from the dynamic tests followed similar trends for the priority and the extent of the elution process.Desorption results from specimens of dynamic tests show a 60:1 concentration ratio leading to a 186 mg/L Sc-rich solution.

Soil−water characteristics of weathered crust elution-deposited rare earth ores

The permeability of the weathered crust elution-deposited rare earth ores directly affects the efficiency of in-situ leaching.The soil−water characteristic curve(SWCC)is an important constitutive relation for calculating the permeability of ore body,which is related to many factors.Soil−water characteristic tests of rare earth ore samples considering different factors were carried out by using the pressure plate instrument.Effects of dry density,particle size and solution leaching on water holding behavior and the mechanism were investigated.The experimental observations indicate that with the decrease of dry density,the pore ratio increases gradually,and the saturated water content increases.Under the same matric suction,the water content decreases gradually with the increase of particle size,thus decreasing water holding capacity of ore accordingly.In the same water content,matric suction is inversely proportional to particle size.Under the same matric suction,the water content of ore samples after leaching is less than that of the ore samples before leaching,indicating that solution leaching can decrease water holding capacity of ore.

Lattice Boltzmann model for simulation on leaching process of weathered elution-deposited rare earth ore

The lattice Boltzmann model with coupled chemical reaction was proposed to simulate the ion exchange process of rare earth leaching and verified by comparison with both empirical correlation of mass transfer coefficient and unreacted-core shrinking model. By simulation, the zonation phenomenon of leaching reagent in the leaching column was presented, and the breakthrough curve of leaching reagent was obtained. When t=50 s, there existed the saturated and exchange zones, and the leaching reagent concentration decreased gradually from 20 to 9.3 g/L. In accordance with the breakthrough curve, the breakthrough capacity of ion-type rare earth ore and the adsorbed ion concentration of leaching reagent were derived, the time of t=25 s was the breakthrough point of ammonium ion in leaching reagent and the breakthrough capacity of the rare earth ore was 125 g/L. Besides, the chemical kinetics parameters used for the solute transfer process of rare earth leaching were obtained by the simulation and then were used to determine the rate-limiting steps of rare earth leaching process.

Assessment of Potential Nutrient Release from Phosphate Rock and Dolostone for Application in Acid Soils

Finding alternative local sources of plant nutrients is a practical, low-cost, and long-term strategy. In this study, laboratory column experiments were conducted in a completely randomized design to evaluate the feasibility of using phosphate rock and dolostone as fertilizers or acid-neutralizing agents for application in tropical acid soils. The dissolution rates of different particle-size fractions(0.063–0.25, 0.25–0.5, and 0.5–2 mm) of both rocks were studied by citric acid solution at p H 4 and 2 and water, with extraction times of 1, 3, 5, 7, 12, 24, 72, 144, 240, and 360 h. The results showed that the dissolution of both rocks depended on the particle size,leaching solution, and extraction time. The dissolution rate of rock-forming minerals increased as the specific surface area increased,corresponding to a decrease in particle size. In all cases, the release kinetics was characterized by two phases: 1) a first stage of rapid release that lasted 24 h and would ensure short-term nutrient release, and 2) a second stage of slow release after 24 h, representing the long-term nutrient release efficiency. Both rocks were suitable as slow-release fertilizers in strongly acid soils and would ensure the replenishment of P, Ca, and Mg. A combination of fine and medium particle-size fractions should be used to ensure high nutrient-release efficiency. Much work could remain to determine the overall impact of considerable amounts of fresh rocks in soils.