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Rainbow notes ‘highly positive’ initial metallurgical results for Phalaborwa project

24th May 2021

By: Tasneem Bulbulia

Senior Contributing Editor Online

     

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Aim-listed Rainbow Rare Earths has recorded initial results from the ongoing metallurgical test work programme at the Phalaborwa project, in South Africa.

The test work programme is being undertaken by Australian company ANSTO Minerals.

"We are excited by the initial highly positive test work results received from ANSTO, which support our view that Phalaborwa can be developed as a low capital intensity project, with operating costs near the bottom of the global rare earth cost curve,” CEO George Bennet says.

Test work has confirmed the phosphogypsum at Phalaborwa is amenable to simple, direct leaching with low-cost sulphuric or hydrochloric acid without pre-treatment.

In this regard, initial recoveries of rare earths of greater than 70% have been achieved within 24 hours, which will be improved through further optimisations.

Moreover, it is expected that the production of high-value products (mixed rare earth carbonate or separated rare earth oxides) will be possible from the leach solution.

The test work also confirmed that the phosphogypsum contains exceptionally low levels of radioactive elements – uranium and thorium – when compared with other rare earth projects.

In this regard, radioactivity controls are expected to be required for the shipment of the rare earth products and no expensive redeposition measures should be required for the leached phosphogypsum residue.

The test work results, to date, support the expectations that a simplified processing flow sheet can be developed and optimised from the original flow sheet compiled by previous owner chemicals company Sasol to recover the rare earths without the high-cost, energy- and reagent-intensive mining, crushing, milling, primary beneficiation, cracking and uranium/thorium removal costs associated with a typical rare earth project.

The next phase of testing, currently in progress at ANSTO, is focussed on the optimisation of leach recovery and acid consumption and the initial selective recovery of the rare earths from the leach solution.

“The high initial recovery of rare earths reported from the gypsum via a simple 24-hour acid leach process at ambient temperature and pressure is a major benefit as we are essentially dealing with a 'cracked chemical feed' that has occurred before the gypsum residue was deposited. 

“As we review further optimisation to increase the recovery of rare earth elements and reduce reagent consumption, we will carry out a thorough cost/benefit analysis to ensure each step increases the overall value of the project.

“These initial test work results confirm my belief that Phalaborwa, by its nature, will probably be the fastest global rare earth development project to get to the mixed rare earth carbonate producing stage. 

“We are targeting delivering production from Phalaborwa in an accelerated timeframe, which can only be achieved because of the unique nature of the project with simple processing requirements,” comments Bennet.

The test work, to date, has confirmed that the Phalaborwa tailings are expected to be benign, negating the need to manage multiple tailings facilities which adds increased costs for many global rare earth projects. 

The concurrent rehabilitation of two historical gypsum stacks reduces the environmental footprint in an ecologically sensitive area.

Further work is planned to confirm the leach characteristic variability of the stacks to support a preliminary economic assessment for the Phalaborwa project.

Further optimisation and processing development work will then be undertaken prior to the completion of a full feasibility study.

Edited by Chanel de Bruyn
Creamer Media Senior Deputy Editor Online

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