Sulfuric Liquor Research Articles

Development of a conceptual direct solvent extraction (DSX) route and a flowsheet to produce purified concentrated cobalt and nickel solutions representing sulfuric acid leach liquor of laterite

Direct solvent extraction (DSX) was applied to produce purified concentrated Ni and Co solutions from a synthetic sulfuric liquor containing Ca, Cu, Mg, Mn, and Zn as impurities, which simulates the solution obtained by the sulfation-roasting-leaching process after precipitation of Fe, Al, and Cr. The commercial extractants Versatic 10, Cyanex 272, D2EHPA, TBP were used in 3 solvent extraction circuits. In the first circuit, operated at 40 °C, Versatic 10 (0.5 M) fully extracted Cu, Zn, Ni, and Co in 3 stages at O/A = 2:1, and pH 6.5, leaving remaining Mn (54% was extracted) and most of the Ca and Mg in the raffinate. The co-extracted Ca and Mg were fully scrubbed off the loaded Versatic 10 in 2 stages at O/A = 5:1, and pH 6.5. The other metals were stripped out of the Versatic 10 extract using a synthetic Ni spent electrolyte (60 g/L Ni, 2 M H2SO4) in 2 stages at O/A = 9:1. This loaded strip liquor was subjected to a second circuit with Cyanex 272 (0.64 M) operated at 50 °C. Three stages were required to fully extract Co, Cu, Mn, and Zn (O/A = 2:1, pH 4), whereas the raffinate containing 82 g/L Ni was deemed suitable for electrowinning. The co-extracted Ni(II) was fully scrubbed off the loaded Cyanex 272 in only 1 stage at O/A = 5:1, and pH 4. All Co, Cu, Mn, and Zn were stripped out from the scrubbed loaded Cyanex 272 in 2 stages at O/A = 10:1 using a synthetic Co spent electrolyte (45 g/L Co, 1 M H2SO4). The raffinate containing 58.4 g/L Co was submitted to a third circuit using a D2EHPA (0.6 M) + TBP (0.73 M) synergistic system operated at 50 °C. Zinc(II) was fully extracted by the D2EHPA + TBP system in 2 stages at pH 2 and O/A = 1:3, while Mn(II) and Cu(II) were fully extracted from the Zn-depleted raffinate in 2 stages at pH 3.5 and O/A = 2:1. The raffinate containing 58.3 g/L Co was deemed suitable for electrowinning. Copper(II), Mn(II), and Zn(II) were stripped out from the loaded D2EHPA + TBP in 3 stages at O/A = 2.5:1 using 1 M H2SO4. The real number of moles of extractants involved in the extractions and apparent equilibrium constants were estimated for all circuits. A flowsheet of the purification conceptual route is presented.

Use of iron ore concentrate processing waste for treatment of copper sulphate liquors

Use of iron ore concentrate processing waste for treatment of copper sulphate liquors

Comparative Studies on Hydrometallurgy and Pyrometallurgy to the Extraction of Beryllium from Decrepitated Beryl from Wadi El Gemal Region, Eastern Desert, Egypt

Comparative Studies on hydrometallurgy and pyrometallurgy to the extraction of beryllium from decrepitated beryl from Wadi El Gemal Region, Eastern Desert, Egypt are carried out in this work in short, useful summary. Beryl is one of the important ore mineral constituents of the mineralized zones at Wadi El Gemal area, Eastern Desert, Egypt. Extraction of beryllium from beryl ore involves both (a) pyrometallurgical techniques through roasting of beryl with Na2SiF6 followed by leaching of roasting beryl with commercial (dilute) H2SO4 (b) hydrometallurgical processing techniques of beryl through direct leaching with H2SO4 to produce directly sulfate liquor. 88% of beryllium was extracted by roasted beryl with Na2SiF6 at 850°C for 1.5 hours and leaching the roasted product with 25% H2SO4 AT 85 ° C for 3/4 hour. On the other hand, 95 % of beryllium was extracted directly after 20 minutes by direct leaching at 280°c with 10 mol/liter H2SO4. Therefore, this work sheds light on the study of the factors affecting both forms of beryllium extraction.

A Suggested Procedure for Recovery of Cerium from Sulfate Liquors of Egyptian Rosetta Monazite

A Suggested Procedure for Recovery of Cerium from Sulfate Liquors of Egyptian Rosetta Monazite

The transformation and enrichment of rare earth sulfate in Bayan Obo ore water leaching solution by dibenzyl phosphate based extraction-precipitation method

Chemical precipitation and solvent extraction have been widely used to transform rare earth (RE) sulfate into RE chloride in the field of hydrometallurgical process for monazite and bastnaesite, but there are some industrial challenges such as consuming a large amount of chemical reagents and producing wastewater. As for the transformation field of RE sulfate liquor, the development of sustainable and efficient transformation technology is an important industrial challenge. In this study, one step transformation and enrichment of RE sulfate into RE chloride using dibenzyl phosphate (DBP), diphenyl phosphate (DPP), triphenyl phosphate (TPP), diphenylphosphinic acid (DPPO) and 1,1′-binaphthyl-2,2′-diylhydrogenphosphate (DHGP) was studied. Unlike common solvent extraction, volatile organic solvents are not required in the extraction-precipitation processes. Different from the common chemical precipitation, the extraction-precipitants can be recycled. The investigation shows that DBP has a higher precipitation efficiency of RE than those of DPP, DPPO, TPP and DHGP. RE can be selectively separated from Mg and Ca by DBP. After stripping with concentrated hydrochloric acid, a high-concentration rare earth chloride solution of 187 g/L is obtained. This new method is easy to be implemented and has shown the potential of saving resources and protecting the environment.

Manufacturing reactive magnesia from nickel laterite waste solution via nesquehonite precipitation

Nesquehonite is an attractive magnesium precipitation product as it sequesters CO2 and exhibits good filterability. Upon calcination, high-quality reactive magnesia is produced. As part of the hydrometallurgical processing of nickel, magnesia is used as a precipitating agent to recover nickel and cobalt in the form of a Mixed Hydroxide Precipitate (MHP). However, a waste solution with elevated concentration of magnesium is formed which can be an environmental liability. Chemical thermodynamic equilibrium modeling of magnesium carbonate precipitation from magnesium sulfate liquor predicted a high reaction extent of 99% could be achieved. Magnesium carbonate precipitation experiments were carried out by gradually mixing sodium carbonate solution and synthetic industrial liquor in a batch reactor at 25 °C, while monitoring solution concentrations and pH, used to estimate the supersaturation index. Calcination of the resulting solid at temperatures ranging from 450 to 650 °C produced magnesia with acetic acid activities ranging from 14 s to 41 s. The most reactive magnesia was obtained at the lower temperature of 450 °C with an activity of 14.7 ± 0.6 s, which meets industrial product specifications. Periclase was identified as the dominant magnesia mineral phase along with thenardite as a minor component.

Selective recovery of zinc from mining sulfuric liquor employing aqueous two-phase systems

Zinc recovery is extremely important due to the chemical and physical properties of this metal. Liquid-liquid extraction technique allows the selective recovery of zinc, leading to a high purity product. For the first time, a concentrated mining sulfuric liquor as a stock solution for in situ preparation of an Aqueous Two-Phase System (ATPS) in a hydrometallurgical process. This liquor is an overly complex solution with a high content of metal ions, especially Zn2+ and Mg2+. ATPS technique has already shown good results when compared to traditional solvent extraction techniques and can be considered a greener technique. The proposed method was optimized to obtain selective Zn2+ extraction by studying the parameters: the nature of the ATPS-forming polymer and their concentration in the stock solution; the effect of the salt added to the system; the concentration of extractant agent and the mass ratio between both phases. The optimized methodology made it possible to extract (91.5 ± 0.1)% of Zn2+ and (18.2 ± 0.1)% of Mg2+ from the liquor in three extraction steps. In the stripping step which used NaOH as the precipitating agent, about 65 % of Zn2+ was selectively recovered at pH = 6.00 and at pH = 9.00 the recovery of Zn2+was close to 80 %. Furthermore, for the first time it was proven that the polymer and the extracting agent (following the stripping step) are reusable components of the ATPS. A high extraction efficiency (%EZn ∼ 45 %) was achieved in one extraction step using the recycled extraction phase without any adjustment.

Processing of ferromanganese fumes into high-purity manganese sulphate monohydrate

ABSTRACT A novel process for recovering manganese (Mn) values from two types of ferromanganese (FeMn) fumes (wastes from smelters) was developed incorporating several stages of leaching, roasting, and precipitation. Fumes containing high K (as K2O) were first leached in water at ambient conditions to recover K, purified to remove metal impurities, and precipitated as 99.9% pure K2SO4. The residues containing Mn and remaining impurities were then leached in sulfuric acid at 80 °C using oxalic acid as reductant yielding Mn sulphate liquors. The leach liquors were then purified to remove Fe at 95°C as jarosite at pH 2.8 and Fe(III) hydroxides at pH 5.5. Base and transition metal impurities were removed as sulfides. K, Na, Ca, and Mg were separated from Mn in a novel step based on precipitation of Mn hydroxide from the Mn sulphate liquors. Subsequent redissolution of Mn hydroxide in sulfuric acid under reducing conditions using oxalic acid produced a high purity Mn sulphate liquors containing <5 ppm of these impurities. After evaporation by boiling manganese sulphate monohydrate (MSM) was crystallized, achieving purity >99.5%. Another fume containing oil contaminants having low K was subjected to sulfation roasting to produce Mn sulphate. The calcine was water leached to produce Mn sulfate liquors and treated in a similar process to make high purity MSM. Novelty aspects of the proposed process include the recovery of K as a by-product and separation of Mn2+ from other impurities by its selective precipitation to produce a high purity Mn sulphate solution for MSM recovery. Implications: Ferro-manganese smelters discharge wastes (fumes) that are collected by bag filters or electrostatic precipitators and then store them on the ground with coverage to prevent their dispersion into the surrounding atmosphere. The work presented propose a process to reprocess these wastes into high purity manganese sulphate monohydrate (MSM). Processing of wastes containing high potassium as KOH also yields high purity potassium sulfate used as fertilizers. Some smelters spray oil onto the fume dumps to prevent material being blown onto the surrounding area. The oil-contaminated fumes have to be first roasted to burn off the oil, before they can be processed. The process developed therefore converts a hazardous waste into high purity MSM and potassium sulphate used in many applications.

Purification of concentrated nickel sulfuric liquors via synergistic solvent extraction of calcium and magnesium using mixtures of D2EHPA and Cyanex 272

A synergistic solvent extraction circuit consisting of D2EHPA and Cyanex 272 was applied to purify a concentrated Ni sulfuric solution ([Ni] = 88 g L−1, [Mg] = 3.1 g L−1, [Ca] = 0.5 g L−1) similar to the MHP industrial liquors that feed the electrowinning step. The temperature was identified as a key parameter to optimize Mg extraction as well as to promote the selective recovery of co-extracted Ni in the extraction stages and make the stripping of Ca feasible using HCl as a stripping agent. Ca was crowded out by Ni from the loaded D2EHPA + Cyanex 272 solution and limited the operating pH range between 2 and 4. Under optimum conditions, 98.0% Ca and 98.4% Mg were simultaneously extracted in two and three theoretical stages by D2EHPA (0.30 M) + Cyanex 272 (0.32 M) mixture (pH 4, A/O ratio = 0.7 and 50 °C). Co-extracted Ni was selectively recovered (99.7%) from the loaded D2EHPA + Cyanex 272 using [H2SO4] = 0.063 M in three stages (O/A ratio = 1 and 50 °C). Ca and Mg can be completely stripped out from the loaded D2EHPA + Cyanex 272 at 50 °C in only 1 ([HCl] = 3 M, O/A ratio = 5) or two theoretical stages ([H2SO4] = 1 M, O/A ratio = 2). The purified liquor containing 80 g L−1 Ni (99.9% purity) can be directed for the electrowinning step to produce Ni cathodes. Extraction and stripping kinetics are rapid (equilibrium reached within 5 min). Thermodynamic analysis was done to support the synergism/antagonism trends observed experimentally.

Selective Water Leaching of Sulfated Rare Earth Ore and Impurity Removal from a Rare Earth Sulfuric Liquor

The objective of this work was to assess the influence of parameters such as residence time, solid content, and temperature in a process route towards purified rare earth liquor which could be adequate to produce marketable rare earth products. The steps of the process route proposed in this study comprised water leaching of a sulfated rare earth ore and removal of impurities through the purification of the rare earth sulfuric liquor, which is the product of the water leaching step. The sample used in the water leaching experiments was a sulfated rare earth ore produced by the reaction of a beneficiated rare earth ore with sulfuric acid followed by roasting at 700 °C for 2 h in a muffle furnace and cooling at 20 °C. The water leaching experiments showed that the best condition comprised a residence time of 30 min, temperature of 20 °C, and solid content of 10% w/w, resulting in a recovery of 71.3% of the rare earth elements (REE) and a lower impurity extraction, e.g., only 15.0% of Fe, representing the main impurity in the rare earth ore. Even when presenting low amounts of impurities, the rare earth sulfuric liquor still needed to be purified before it can be used in the production of marketable rare earth products. In the study, the rare earth sulfuric liquors were purified in two consecutive neutralization steps, first by dosing the limestone pulp to pH up to 3.5 and secondly by adding the lime pulp to raise the pH from 3.5 to 5.0. The application of two consecutive purification steps at 20 °C resulted in the highest overall REE recoveries (65.4%) throughout all the steps of the process, being 71.3% in the water leaching, 99.6% in the partial purification with limestone pulp, and 92.1% in the purification with lime pulp at 20 °C. Under this condition, there was a total elimination of Fe, P, and Th and a significant reduction in the Al, U, and sulfate concentrations in the purified rare earth liquor. The purified rare earth liquor attained through the experiment is expected to be amenable to be used in the production of marketable products due to the lower impurities/REO mass ratios.

Evaluation of Different Neutralization Reagents in the Selective Removal of Impurities in Rare Earth Sulfuric Liquor

The objective of this study is to assess the impact of different reagents, such as limestone, lime, magnesium oxide, and sodium hydroxide, in experiments carried out in the single purification step and in two consecutive purification steps by raising the pH of a rare earth sulfuric liquor with the aim to remove or reduce the impurity concentrations in the rare earth sulfuric liquor. The choice for the best purification condition was made based on the minimum loss of rare earth elements (REEs), reagent consumption, and residue generation. The exploratory experiments show that it takes place in the two consecutive purification steps, the first one consists in dosing the limestone pulp until it reaches a pH of 3.5 followed by an addition of a lime pulp reaching a pH of 5.0. Under this condition, the results were a total removal of Fe3+, PO43−, and Th4+ ions and a reduction of 99%, 87%, and 37% w/w in the Al3+, UO22+, and SO42− concentrations, respectively, in the purified rare earth liquor. Furthermore, the lowest REE losses (8.3% w/w) and reagent consumption (4.3 kg/m3) and also a low residue generation (7.5 kg/m3) were observed in this condition. Despite reaching similar results regarding impurity removal, the experiments done with the addition of limestone, lime, magnesium oxide pulps, and sodium hydroxide solution in the single purification step, where the pH was raised to 5.0, presented higher REE losses (64.9%, 42.5%, 44.8%, and 60.9% w/w, respectively) and a higher residue generation (43.2, 25.1, 11.1, and 13.6 kg/m3, respectively). This occurred due to the co-precipitation of salts containing rare earth elements in their composition. The experiments conducted with limestone, lime, and MgO resulted in a higher consumption of reagents, while the same result was observed when NaOH was used (4.3 kg/m3). In the experiments carried out with the addition of magnesium oxide and sodium hydroxide, the respective purified rare earth liquors presented a high concentration of magnesium, sulfate, or sodium, which could impact the quality of the marketable rare earth salts, whereas the salts obtained under the best condition observed in this study seem to be amenable for use as raw material in an attempt to obtain rare earth products with an acceptable chemical quality.

Selective cerium removal by thermal treatment of mixed rare earth oxalates or carbonates obtained from non-purified rare earth sulphate liquor

One of the world́s most abundant of all the rare earth elements (REE) is cerium. It represents about 50 wt% of total REE content in the main rare earth minerals used industrially (monazite and bastnaesite). However, cerium is not a valuable product if compared with the other REE. In the most current pyro-hydrometallurgical processes routes, a high amount of cerium goes to the rare earth liquor, incurring in high operational and capital costs in the solvent extraction step used in the separation of each individual rare earth element. In this context, this study evaluates the use of thermal treatment for rare earth oxalates and carbonates and also hydrochloric acid leaching of calcination products for selective separation of cerium from other REE. This investigation also sheds light on the mechanisms involved in the processes proposed. For this purpose, mixed rare earth and cerium oxalates, also mixed rare earth and cerium carbonates were used as precursors. The mixed rare earth salts used in the experiments were generated from a non-purified rare earth sulphate liquor. The results indicated that the minimum required temperature to fully decompose the mixed rare earth oxalates, cerium oxalate, mixed rare earth carbonates and cerium carbonate to their respective rare earth oxides (REE2O3) or CeO2, was 1100 °C, with 1 h of residence time. In the experiments carried out with mixed rare earth oxalates, Ce3+ was not fully oxidized to Ce4+, it formed a mixture of Ce2O3 and CeO2 represented by Ce4O7, which was completely dissolved in the hydrochloric acid solution (37 wt%). Therefore, in such case, cerium was not selectively removed from the mixed rare earth oxalates by thermal treatment and hydrochloric acid leaching. On the other hand, the Ce3+ presented in the composition of the pure cerium oxalate or carbonate was fully oxidized to Ce4+ (CeO2) under the same condition of calcination. As expected, CeO2 was not dissolved by the hydrochloric acid solution (37 wt%). It was concluded that mixed rare earth carbonates generated Ce0.60Nd0.40O1.80 (Ce1-xNdxO2-x/2, x = 0.40) when calcined under the same condition. This crystalline structure was not also dissolved by hydrochloric acid solution (37 wt%). As a result, a process flowsheet was proposed to remove cerium selectively from a rare earth ore.

Selective Precipitation of High-Quality Rare Earth Oxalates or Carbonates from a Purified Sulfuric Liquor Containing Soluble Impurities

The purity of rare earth products depends on the ability of the reagents used to selectively promote the precipitation of the rare earth elements (REE) from impurities present in sulfuric liquors. The present study aims at investigating the conditions required to precipitate REE, either as rare earth oxalates or carbonates, from purified rare earth sulfuric liquor with a low Al3+ and UO22+ and a very high Ca2+, Mg2+, Mn2+, and SO42− impurity content. The rare earth sulfuric liquor was obtained in a previous study by the reaction of a rare earth ore with sulfuric acid, pyrolysis at 700 °C/2 h, cooling at 20 °C, and water leaching. The impurities such as Fe3+, Th4+, and PO43− were completely removed from the liquor in two consecutive neutralization steps. In order to recover the REE, the purified rare earth liquor was then treated with oxalic acid and sodium carbonate. Rare earth oxides (REO) precipitated with oxalic acid displayed a very high purity (99.2% w/w) and low impurity content. In contrast, the rare earth carbonates precipitated with sodium carbonate presented a comparatively lower REO content (68.5% w/w) and 94.2% of purity, but with a higher content of impurities. Better precipitating conditions were achieved at 60 °C, compared with 20 °C, and under stoichiometric reagent consumption, with REE precipitation efficiencies higher than 96%. The dosage above the stoichiometric condition caused the precipitation of calcium oxalates and co-precipitation of rare earth sulfates when oxalic acid is used, and precipitation of calcium, manganese, and uranium carbonates and also a co-precipitation of rare earth sulfate when sodium carbonate were used. An integrated flowsheet to produce a high-quality rare earth product from rare earth sulfuric liquor containing some impurities is proposed.

Selective precipitation of rare earth from non-purified and purified sulfate liquors using sodium sulfate and disodium hydrogen phosphate

The conventional hydrometallurgical process routes for the recovery of rare earth elements (REEs) from ores employs sulfuric acid. After being leached, the rare earth sulfate liquor presents impurities that need to be removed before they can be used in the production of marketable products. In this sense, a non-purified rare earth sulfate liquor obtained from a rare earth mineral processing and containing low rare earth oxides (REOs) concentration (∼4.6 g/L) and high Ca2+, Mg2+, Mn2+, Fe3+, Al3+, Th4+, UO22+, PO43− and SO42− content were used in this study. In order to remove all the Fe3+, Th4+ and PO4−3 ions and reduce Al3+, Ca2+, UO22+ and SO42− concentrations, the liquor was purified in two consecutive steps: first by addition of limestone to pH of 3.5 and then with a dosage of lime until it reached a pH of 5.0. Only about 7% of the REEs mass feed in the liquor was lost in the purification step. The REEs precipitation experiments were carried out with two liquors, non-purified and purified, using Na2SO4 and Na2HPO4 as reagents. The rare earth products with the highest purity were obtained with purified rare earth sulfate liquor. In the best condition, the consumption ratio was 0.31 ton of Na per ton of REEs and it resulted in the precipitation of 100% of the REEs feed in the liquor by addition of Na2HPO4. In the experiments in which Na2SO4 was used, the consumption was 0.82 ton of Na per ton of REEs and only 88% of the REEs feed was precipitated. The temperature to precipitate the REEs using Na2HPO4 ranged from 20 °C to 70 °C, whereas precipitation with Na2SO4, only occurred at 70 °C. The rare earth products obtained with Na2SO4 (sodium and rare earth double sulfate) and with Na2HPO4 (a mixture of rare earth phosphate and sodium and rare earth double sulfate), containing respectively 41.4% w/w and 42.9% w/w of REOs, seemed to have enough purity to be processed in downstream steps. As a result, a flowsheet for a process route to recover the rare earth elements from a non-purified rare earth liquor was proposed.

Effective Recovery of Pulp Waste in the Innovative Production of Environmentally Acceptable Wood Composites

However, as a result of efforts to improve the environment, while maintaining the required qualitative characteristics, global developments in the field of wood materials (as raw materials of the 21st century) have led to the development of new or effective modifications of existing technologies, focusing on reducing the emission of formaldehyde and other toxic components in polycondensation adhesives applied to the preparation of composite wood materials. The suggested problem means reciprocal replacement of the toxic components of currently produced polycondensation adhesives (especially phenol-formaldehyde), e.g. kraft black liquors, which can be isolated as a secondary raw material from the pulp and paper industry in the production of sulphate pulp. Sulphate liquros are characterized by a relatively low reactivity to formaldehyde, thus are requiring their incorporation into the polymeric matrix of mixed lignin-phenol-formaldehyde polycondensate. For this reason, it is necessary to modify the reactivity of the original kraft black liquors by the modification reactions. New methods of processing sulphate liquors are focused only on the use of some components of black liquors or on the production of high-price products, which can be applied economically but especially “eco-friendly” in the preparation of wood composite materials as adhesives. The article deals with the problem of effective utilization waste of kraft black liquor from pulp and paper industry, which are possible apply in various modification treatment as reciprocal replacement of polycondensative adhesives for preparation of wood based composite materials. In our research, we focused on proposal of innovative adhesives mixtures which were applied for production of eco-progressive wood based composite materials with better hygienical properties and significantly reducing the content of toxic formaldehyde in adhesive mixtures.

Solvent extraction of copper from an industrial sulfate liquor using Chemorex CP-150

The extraction behavior of Cu(II) ions from a real sulfate liquor obtained from the heap leaching stage of a copper oxide ore was investigated using a chelating reagent, Chemorex CP-150 in kerosene. A comparative study was also carried out on the extraction capability of Cu(II) ions using other solvents including D2EHPA and Cyanex 272.Chemorex CP-150 demonstrated an effective and selective extraction performance of copper with the amount of extracted Fe less than 15%. Also the results obtained indicated that more than 66.4% and 96.99% of Cu were transferred to the organic phase in a single extraction stage using 15% (v/v) Chemorex CP-150 at the A:O phase ratios of 1:1 and 1:4, respectively. In addition, the McCabe-Thiele diagram exhibited that two extraction stages were required to achieve the maximum amount of Cu at a 1:1 phase ratio under the optimal conditions (25 °C, pH 2.5, and 20 min contact time). Also, thermodynamic data proved that the extraction process was slightly endothermic (ΔH = 7.62 kJ/mol), indicating the relatively smaller heat effects on the formation of a single complex species (CuR2). Stripping of copper from the loaded organic phase was also conducted, and it was found that ~99.38% copper could be recovered using 165 g/L H2SO4 at a 2:1 A:O phase ratio after 5 minutes stripping.

Recovery of uranium, thorium and rare earth from industrial residues

This paper addresses the development of a process to recovery uranium, thorium and rare earth elements from an industrial residue, with a subsequent removal of U and Th from the liquor generated. Sulfuric acid digestion followed by water leaching was found to be the best method to solubilise the metals. The acid digestion was carried out with an acid sample ratio of 700 kg t−1 and a reaction time of 2 h, without temperature control. The water leaching step was performed at room temperature (25 ± 2 °C), with 1 h of mechanical stirring and 20% of solids. Under these conditions, a metal dissolution of 94%, 81% and 97% was reached for the REE, Th and U, respectively. After the metal solubilisation, a sulfuric liquor containing 0.08 g L−1 Th, 0.35 g L−1 U, 9.1 g L−1 REE, 16 g L−1 Al, 7.8 g L−1 Fe, 0.47 g L−1 Ca, 0.75 g L−1 Zn and 0.1 g L−1 Si was formed. This liquor was used in the solvent extraction stage in order to separate Th and U from the REE, as well as from other metals. The effect of the type and extractant concentration, acidity of the liquor and type and concentration of the stripping solution were investigated. The results showed that 97% of the uranium and 94% of the thorium were extracted by a mixture of 0.05 mol L−1 of Primene JM-T and 0.1 mol L−1 of Alamine 336, in a single stage. The stripping from the loaded organic phase for the simultaneous removal of U and Th can be effectively done by using 1.7 mol L−1 NaCl solution at pH 1.2.

Experimental study on hold-up, characteristic and slip velocities in a horizontal pulsed sieve-plate column and uranium reactive extraction condition in aqueous phase

The uranium extraction efficiency from sulfate leach liquor and the hydrodynamic behavior of the reactive extraction system was studied in the horizontal pulsed sieve-plated column. The effects of operating parameters and reactive condition were investigated. The obtained results showed that an increase in pulse intensity caused the decrease of dispersed phase hold-up and increase slip velocity. The slip velocity in the reactive uranium extraction situation was greater than that of the system without the reactive extraction due to the faster upward movement and more buoyancy of drops. The uranium extraction efficiency has a direct relationship with increasing pulse intensity and the dispersed phase flow rate, whereas has an indirect relationship with increasing continuous phase flow rate. Also, with comparison between experimental results and several empirical correlations for characteristic velocity, the Pratt model was chosen for prognostication of this parameter. The experimental results compared with the proposed correlations obtained from the previous studies demonstrated that the previous correlations have any reasonable accuracy to prognosticate the hold-up as well as the characteristic and slip velocities in this column. Therefore, the semi-empirical correlations were determined for prediction of hydrodynamic parameters as functions of the physical properties of systems and operating conditions. It can also be concluded that the horizontal pulsed sieve column is suitable for extraction of uranium from the sulfate liquor by Alamine 336 with extraction efficiency of approximately 99%. Therefore, it is a good alternative in radioactive processes, especially in places with height limitation.

Application of Commercial Adsorbent for Rare earth elements - Uranium Mutual Separation and Purification

The treatment of rare earths sulfate liquor contaminated with traces of uranium as radioactive contaminates utilizing lewatit mono plus M500 was studied. Adsorption behavior was studied by batch experiments to determine the optimum conditions for uranium removal. The obtained equilibrium data were found to be satisfactory fitted with Langmuir isotherm and the second order rate equation. Also, elution process was achieved by 2M NaCl/1M HCl solution and the reuse of sorbent remains appreciable. A marketable pure product of rare earth oxide was prepared in addition to pure sodium diuranate containing total uranium content of the starting REEs cake.

A novel procedure for processing of the xenotime mineral concentrate of southwestern Sinai

A novel procedure for processing the xenotime mineral concentrate of southwestern Sinai (55.4% RE2O3 and 0.9% U3O8) has been studied. This procedure is based on leaching of uranium and rare earths from the xenotime concentrate using ferric sulfate solution by hydrolytic leaching with ferric ion, wherein ferric iron is precipitated to generate acid for the leaching step. The obtained slurry is washed by water and sulfuric acid. The relevant conditions of the ferric ion leaching of the concentrate and the washing step have been optimized. From the obtained sulfate liquor, rare earths are directly precipitated as oxalates. Uranium is extracted from the REE-free sulfate solution using ion exchange resin Amberlite IRA-400. Highly pure oxide products of the two interesting metal values, REEs and U, have properly been prepared.