Metso are one company that has addressed the problem of sodium...

Metso are one company that has addressed the problem of sodium sulphate waste by developing a process that does not use sulphuric acid.

I believe Piedmont are keen to use this process at future refining plants that they want to develop.

“Through the R&D efforts undertaken by Avalon and Metso, the proprietary lithium hydroxide process represents a far more sustainable conversion method compared to conventional acid roasting. The process operates in an alkaline state and utilizes pressure leaching, which is unique for lithium conversion, eliminating the use of sulphuric acid, and with no production of sodium sulphate as a biproduct. Instead, a substance called Analcime – an inert solid aluminium silicate – is produced, as well as calcium carbonate. Importantly, both substances have commercial uses in industrial building applications and other industries. The method also reduces overall air emissions”

https://www.mining.com/metso-expands-alliance-with-avalon-for-lithium-processing-in-ontario/