"Getting these recoveries at PH1 at atmospheric pressure is very good."... no, it's very average but potentially very expensive. Nobody to my knowledge has funded development of an 'ionic' clay hosted deposit at pH=1 yet, thouigh IXR are the most developed. They claim 10-15g/L H2SO4 acid to get pH=1 and the required recoveries to potentially7 be economic (ie colloidal and non-ionic bonded REE). Must be 25-50 companies mining the market like OD6 on RE geochem anomalies, high acid input recoveries, blended with kaolin or whatever bi-product to try and make bank.
This paper from a few years ago spells out why China (and them Myanmar, Vietnam etc) came to dominate RE production with ICDs. Good recoveries with cheap as chips ammonia-salt leach at pH=4 neutral like conditions, temperature and pressure (in situ basically). No question with enough acidity REs can ve stripped from clay into solution and precipitated into a MREC filter pressed sample. With enough acidity you can do it from any number of RE minerals... it's the cost and practicality that matters...
If you're doing calcs then you must understand chemistry. pH is a log scale, meaning each pH number lower is 10 times more acidic. So pH=1 is 1000 times more acidic than ph=4, 5000 times more acidic than pH=4.5, thats a lot more acid addition before considering how much Ca needs to be sterilised before pH will fall from 4 (CaCO3 chews up acid like pacman). Please don;t conflate RE extraction from ionic clays with HPAL nickel extraction from laterites... any credibility goes out the window.
There is only one IC deposit outside Asia with comparable low cost ammonia salt leach recoveries at moderate pH and that is Meteoric's new Brazilian project (I don;t hold, never held, should have been watching closer lol). I haven't looked into acid consumption specifically, but this is the type of grades, thickness, leach conditions and recoveries that can compete financially in a global RE market.
