The RapidSX™ Process
IMC has developed the RapidSX™ process, a dramatically improved solvent-extraction (SX) process for the separation and purification of rare-earth elements (REEs), nickel (Ni) and cobalt (Co), and other important metals. The patent-pending process significantly reduces the number of process steps required for SX as well as the physical footprint of operations. The time to reach process equilibrium is also significantly reduced, from weeks in conventional SX systems, to a few days using the RapidSX approach. The process also reduces the quantities of organic reagents required and the power requirements for equipment operation, as well as the amount of inventory required to be loaded into the system at any one time.
The result is a process that can produce commercial-grade end products, at a fraction of the capital and operating costs of conventional systems, and in a fraction of the time normally required for such processing.
SX is a liquid-liquid process, and the standard method used for separation and purification of elements and compounds in a wide range of industries. It is most notably used as a processing step in the extraction of various metals from ores and concentrates.
A typical SX chemical circuit starts with a feed solution, a concentrate containing target metals of interest, which have been dissolved in an aqueous solution, such as nitric or hydrochloric acid. The feed is then mixed or contacted with an organic solution, that contains one or more extractants that are used to target one or more of the metals in the aqueous solution.
In the initial extract stage, the target metal ions react with the extractant in the organic phase, leaving the other metals behind in the aqueous phase, known as the raffinate. The aqueous and organic phases are immiscible, and after allowing the process to go to completion, the two phases are allowed to settle out.
The loaded organic phase is then processed in the scrub stage, to remove any non-target metal ions that were co-extracted with the target metals in the first unit process. This is accomplished by contacting the organic phase with additional aqueous solution, into which the non-target ions are extracted and returned back to the extract stage. This eventually results in a high-purity organic solution.
The scrubbed organic solution is then passed to the strip stage, where fresh aqueous solution is used to strip or remove the target metal ions out of the organic phase, and back into the aqueous phase. The result is referred to as the strip solution.
The raffinate and strip solutions from the SX circuit may either be finished products of the SX process, or may need to transferred to additional SX circuits, for further separation of metals to occur.
In addition to the above unit operations, a saponification or pre-neutralization stage may be used prior to extract, to pre-load the organic phase with metal ions, and a wash or regeneration stage may be used after strip, to clean the organic phase of any residual metal ions, prior to recycling back to the beginning of the SX circuit.
Some metals are much more difficult to separate from each other than others – the REEs are a case in point. In such cases, the extract, scrub and strip unit operations will contain multiple individual processing steps – typically mixer-settlers units in conventional SX circuit. The associated low separation factors (the ability to separate elements with high yields and purities) in such systems, means that the process has to be repeated over and over again within each unit operation.
Such systems are therefore highly complex, expensive and the process is time consuming. A conventional SX circuit for the separation of the light REEs La-Ce-Pr-Nd into La-Ce and Pr-Nd, for example, may contain as many as 90 mixer-settler units. More than a dozen SX circuits would be required to produce a suite of individual, high-purity REE products – over 1,000 mixer-settler units in total.
The RapidSX process combines the proven chemistry of SX with a new approach to allowing the organic and aqueous phases to interact during processing, using proprietary column reactors. The columns are designed to increase the process kinetics within each unit operation, while minimizing the settling times required after each process step occurs.
The RapidSX process reduces the number of process steps required in each SX circuit by up to 85-90%, significantly reducing the physical footprint of operations. The time to reach process equilibrium is also significantly reduced, from weeks in some conventional SX circuits, to a few days using the RapidSX approach. The process also reduces the quantities of organic reagents required and the power requirements for equipment operation, as well as the amount of inventory required to be loaded into the system at any one time.
The result is a process that can produce commercial-grade end products, at a fraction of the capital and operating costs of conventional SX systems, and in a fraction of the time normally required for such processing.
IMC currently operates a pilot-scale RapidSX test facility in Mississauga, Ontario, capable of separating up to 2 tonnes of metals per month. Recent milestones include the separation of commercial-grade REEs, Ni and Co. the company is actively working to build commercial-scale demonstration facilities for the production of REEs and Ni and Co.