► Preliminary leaching scandium red mud using diluted sulphuric acid conducted. ► A number of solvent extraction systems studied. ► D2EHPA showed high selectivity and extraction of scandium at low ...pH. ► Scandium stripped using strong caustic solution and precipitated by dilution.
The extraction of scandium from an Australian red mud by selective acid leaching was explored and preliminary leaching tests showed that diluted sulphuric acid can be used to leach scandium from the red mud. The recovery of scandium from a synthetic leach solution of the red mud using solvent extraction was studied. A number of extractants were investigated for the extraction of scandium and its separation from the other metals in the synthetic leach solution. It was found that amongst the three acidic organophosphorus extractants studied, D2EHPA performed best. With the organic system consisting of 0.05M D2EHPA and 0.05M TBP in Shellsol D70 under an A/O ratio of 5:1 at pH 0.25 and 40°C, over 99% scandium was extracted and almost no iron and aluminium were co-extracted. The scandium extracted can be stripped from the D2EHPA/TBP system with 5M NaOH to obtain Sc(OH)3 product. A conceptual flowsheet for the recovery of scandium from red mud is proposed.
•A critical review has been provided on the separation of uranium and thorium from rare earths.•The methods used in rare earth industry during rare earth processing are extensively ...reviewed.•Potential methods for the separation of uranium and thorium from rare earths are also summarised.
Rare earths play critical roles in the applications of advanced materials. Recently, the recovery of rare earths from a variety of resources has gained much interest. Radioactive elements of uranium and thorium are usually associated with rare earth deposits. The separation of uranium and thorium from rare earths is often a big concern in rare earth industry in order to reasonably manage the radioactive nuclides. This paper reviews the technologies used for separating uranium and thorium from rare earths in rare earth production, particularly in China. Some potentially applicable methods, such as precipitation and solvent extraction for the separation of uranium and thorium from rare earths in different media were also reviewed.
The economics of membrane distillation (MD) and common seawater desalination methods including multi effect distillation (MED), multistage flash (MSF) and reverse osmosis (RO) are compared. MD also ...has the opportunity to enhance RO recovery, demonstrated experimentally on RO concentrate from groundwater. MD concentrated RO brine to 361,000mg/L total dissolved solids, an order of magnitude more saline than typical seawater, validating this potential. On a reference 30,000m3/day plant, MD has similar economics with other thermal desalination techniques, but RO is more cost effective. With the inclusion of a carbon tax of $23 per tonne carbon in Australia, RO remained the economically favourable process. However, when heat comes at a cost equivalent of 10% of the value of the steam needed for MD and MED, under a carbon tax regime, the cost of MD reduces to $0.66/m3 which is cheaper than RO and MED. The favour to MD was due to lower material cost. On low thermally, high electrically efficient installations MD can desalinate water from low temperature (<50°C) heat sources at a cost of $0.57/m3. Our assessment has found that generally, MD opportunities occur when heat is available at low cost, while extended recovery of RO brine is also viable.
•Carbon tax increases water cost by 16% to 28%, with RO being least sensitive.•With waste heat and carbon tax, MD is the most cost effective technology.•Direct contact MD was shown to concentrate RO brine up to 361,000mg/L TDS.•MD cost can be as low as $0.57 per m3 water treated.•We proposed a cost effective MD mode for harnessing low grade heat (<50°C).
Various titanium metallurgical processes have been reviewed and compared for titanium dioxide and titanium metal, mainly focusing on the future development of hydrometallurgical processes. It is ...recognised that ilmenite is becoming increasingly important due to the rapid depletion of natural rutile. Many processes are commercially used or proposed to upgrade ilmenite to synthetic rutile. Most of these processes involve a combination of pyrometallurgy and hydrometallurgy and are generally expensive.
The commercialised thermo-chemical chloride processes such as Kroll and Hunter processes are batch operations and need higher grade natural rutile or upgraded synthetic rutile and slag as the feed and the involvement of cost sensitive chlorination and thermo steps. Many improvements for the thermo-chemical processes have been made, but they hold little potential for significant cost reductions beyond current technology. The development of the electro-chemical processes for direct reduction of TiO
2 and electro-slag as feed material and
in-situ electrolysis has achieved some success. However, some challenging issues such as redox cycling, feeding, kinetics, control heat balance have to be resolved before scaling-up to commercial applications.
Direct hydrometallurgical leach processes are advantageous in processing abundant ilmenite ores, low energy consumption and produce sufficiently high quality of pigment grade TiO
2 products for a wide range of applications and major demand. Novel BHP Billiton sulphate processes have been developed to improve leaching strategies, separation of metals by solvent extraction, reduced wastes and recycling acids, and very promising for commercial applications in future. Direct chloride leaching processes have been investigated intensively, featuring purification by solvent extraction and reclaiming HCl by hydrolysis or pyrohydrolysis. Caustic leach with high selectivity and titanium dioxide nano-technology has also been developed. Further development of direct leaching ilmenite coupled with solvent extraction for titanium pigment and metal production, is recommended.
► Various titanium metallurgical processes for the production of titanium dioxide and titanium metal have been reviewed and compared including: ► Processes to upgrade ilmenite to synthetic rutile. ► Thermo-chemical Kroll and Hunter processes. ► Electro-chemical processes for direct reduction of TiO
2 and electro-slag and
in-situ electrolysis. ► Direct hydrometallurgical leach processes.
The world rapidly growing demand for manganese has made it increasingly important to develop processes for economical recovery of manganese from low grade manganese ores and other secondary sources. ...Part I of this review outlines metallurgical processes for manganese production from various resources, particularly focusing on recent developments in direct hydrometallurgical leaching and recovery processes to identify potential sources of manganese and products which can be economically produced.
High grade manganese ores (>40%) are typically processed into suitable metallic alloy forms by pyrometallurgical processes. Low grade manganese ores (<40%) are conventionally processed by pyrometallurgical reductive roasting or melting followed by hydrometallurgical processing for production of chemical manganese dioxide (CMD), electrolytic manganese (EM) or electrolytic manganese dioxide (EMD).
Various direct reductive leaching processes have been studied and developed for processing low manganese ores and ocean manganese nodules, including leaching with ferrous iron, sulfur dioxide, cuprous copper, hydrogen peroxide, nitrous acid, organic reductants, and bio- and electro-reductions. Among these processes, the leaching with cheap sulfur dioxide or ferrous ion is most promising and has been operated in a pilot scale. The crucial issue is the purification of leach liquors and the selective recovery of copper, nickel and cobalt is often difficult from solutions containing soluble iron and manganese. For treatment of manganese bearing materials including waste batteries, spent electrodes, sludges, slags and spent catalysts, a leaching or reductive leaching step is generally needed followed by various purification steps, which makes the processes less economically viable.
It is concluded that the recovery of manganese from nickel laterite process effluents which contain 1–5 g/L Mn offers a growing low cost resource of manganese. Part II of this review considers the application of various solvent extraction reagents and precipitation methods for treating such manganese liquors.
An ionic liquid reagent Cyphos IL 101 (trihexyltetradecylphosphonium chloride) was studied for the recovery of cobalt and manganese from the synthetic nickel laterite leach solution containing ...chloride. It is shown that cobalt and manganese were effectively extracted from the solution containing 100g/L Cl with 0.5M Cyphos IL 101 in the pH range of 1.2–4.5, while no significant nickel, magnesium and calcium were extracted. This could lead to a simple and economical recovery of cobalt and manganese from nickel literate leach solutions. For comparison, tests with other reagents including Aliquat 336 (trioctylmethylammonium chloride) and Alamine 336 (tri-octyl (decyl) amine) which have similar molecular structures were also carried out and it was indicated that Cyphos IL 101 was advantageous for its higher extraction of cobalt and manganese. The effect of pH, chloride concentration, organic concentration and A/O ratio on the metal extraction was studied. Metal stripping tests showed that cobalt and manganese were readily stripped using water. Zinc stripping was very difficult with water and it was only achieved from a low Cyphos IL 101 concentration or using ammonia as the strip reagent. A process for the recovery of cobalt and manganese from laterite leach solutions containing chloride using Cyphos IL 101 has been proposed.
•An ionic liquid reagent Cyphos IL 101 was studied for the recovery of cobalt and manganese.•Cobalt and manganese could be efficiently extracted as chloride concentration higher than 80g/L.•Cobalt and manganese extraction with Cyphos IL 101 was much stronger than that with Aliquat 336 and Alamine 336.•Cobalt and manganese could be recovered with Cyphos IL 101 without pH adjustment.
A comprehensive study on the separation of cesium and rubidium from potassium with 4-tert-butyl-2-(α-methylbenzyl)-phenol (t-BAMBP) from a synthetic brine solution containing 20mg/L Cs, 200mg/L Rb ...and 5g/L K was conducted. The effects of alkalinity, t-BAMBP concentration, temperature, A/O ratio on extraction were investigated. It was found that the best conditions to extract cesium and rubidium were using 30% t-BAMBP concentration with 0.1M NaOH feed solution alkalinity under room temperature, for example 22°C, at an A/O ratio of 1. Under these conditions, the separation factor of cesium and rubidium over potassium were found to be 139 and 11, respectively. The kinetics of both extraction and stripping were fast with equilibrium reached within 2min. All extracted cesium and rubidium and 93% potassium were stripped with 0.1M HCl at an A/O ratio of 1:1 in a single contact. A batch continuous test with 5 extraction stages was conducted under these conditions. It was found that over 99% cesium and rubidium were extracted with 19.4% potassium co-extracted. The concentration ratios of potassium over cesium decreased from 216 in the feed solution to 42 in the loaded organic solution and that of potassium over rubidium from 22 to 4.3, resulting in a decrease in concentration ratios of potassium over cesium and rubidium by about 5 times. Further work should target to test feed solution containing sodium and to improve extraction efficiency and selectivity of the extraction system.
•The extraction of Cs and Rb can be conducted under low alkalinity at room temperature using t-BAMBP.•Stripping of both Cs and Rb was not difficult using low acidity solution with fast kinetics.•A five stage semi-continuous extraction process was conducted with complete Cs and Rb extraction.
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