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"Ca sulphate can be sold as a dried dessicant. Calcium phosphate can be sold as a vegetable extract or anti-caking agent and calcium flouride can be sold in the optical lense and optical window market"

It would be nice, only this mixture that cannot be separated!!!

If you make a calculation based on this tables 7.14 and 7.18, then the content of elements in 1 kilogram of filtered precipitations will be approximately As -4 mg, Co - 22 mg, Ni - 17 mg. The bulk of filtered precipitations will most likely consist of a mixture of CaSO4, CaF2, Ca3(PO4)2. But this one is hard to say because there is no data.

Doesn't it seem strange to you that in these tables 7.14 and 7.18 phosphorus and fluorine and many other elements that are found in large quantities in the gypsum stack are not indicated. Upon neutralization, all these elements will end up in filtered precipitations. "The decrease in multi-elements at each stage is shown in Table 7.18. Approximately 56% of all the listed elements precipitated out of solution by a magnitude of at least 85%."There is no table indicating the chemical composition of filtered precipitations, but only "The total mass of the filtered precipitations was 399 grams generated from a starting solution of 4 liters of stack water." It is in this filtered precipitation that all toxic elements will be concentrated.
How many such filtered precipitations will be formed during the production process and how toxic and applicable they are.

Environmental problems associated with the extraction and processing of rare earth elements are known to all. A good example is China.
I consider the gypsum stack recycling project to be promising, as there is a large amount of stock.
However, the recent situation with the Lynas factory in Malaysian makes one think.

https://electrek.co/2023/03/01/tesla-is-going-back-to-ev-motors-with-no-rare-earth-elements/

SmartPunter

What can you say about phosphorus and fluorine?

Aluminum and iron, as well as silicon in acid, are in the form of cations. Silicon in this case is not sand, but silicic acid.
And if heavy metals and their concentrations are not indicated in "Table 7.9: Typical PLS Stream Composition", this does not mean that they do not exist.

"You could literally eat that." - No thanks. It won't add health.

SmartPunter
>>No they don't because they are not present in the gypsum stack.
The precise chemical makeup is listed in the PFS, you might want to read it rather than inventing a problem that doesn't exist.>>

Take a close look at "Table 7.9: Typical PLS Stream Composition"
Element Primary Filtrate (mg/l)
Al 805
Fe 292
P 1.572
Si 1.082
F 4.510
The periodic table has 118 elements!!!!

Tornadotony
SmartPunter
Indeed, acid treatment of a gypsum stack makes it safe and suitable for use in construction work. However, at the same time, harmful and toxic impurities, such as phosphorus, fluorine, heavy metals, pass into the leaching solution. In CIX technology, NdPr is removed from the solution, the rest of the elements remain in the acid.
The situation is similar with acid-polluted lakes containing such harmful and toxic elements.
I have only one question - how toxic will be the waste from the neutralization of process acid and acid lakes.

fulmar29 - The Rainbow presentation says that they neutralize polluted acid lakes. Do you think the resulting waste is non-toxic? As well as acid waste after REE extraction.

Research has already been carried out more than once by many specialists. But none of them gave an answer to the questions of waste toxicity.

Has anyone asked the question - why is phosphogypsum not recycled to this day? Although it has been accumulated in Europe (Spain, Belgium, Poland, Finland and Sweden), in South America (Brazil), in North Africa (Morroco, Egypt, Tunisia) and in many other countries. Its processing is difficult for a number of reasons:
- low content of REE in phosphogypsum, not more than 0.5%;
- low extraction of REE, no more than 70%;
- high operating costs;
- the most important reason - environmental friendliness.
Since the unrecovered, remaining REE and other heavy metals in the gypsum do not allow it to be used further.
During leaching and subsequent extraction of REE, heavy metals accumulate in acid, after neutralization of which a toxic sludge is formed. For China in particular, this is a very big problem.
I hope that all these issues will be resolved by the Rainbow team.

So does anyone know how dangerous they will be:
- precipitation of acid solution neutralization;
- waste CIC/CIC technology.

Does anyone know what the productivity of the pilot plant is?