# Tantalum recovery from alkaline leachates based on magnesium hexatantalate intermediate precipitate

## TL;DR

A new method for recovering tantalum from alkaline solutions is introduced, offering high efficiency and environmental benefits.

## Contribution

A novel magnesium-induced precipitation method for tantalum recovery with over 99% yield is developed.

## Key findings

- Tantalum is precipitated as Mg4Ta6O19·xH2O with x = 16.1 or 24.4 using a Mg/Ta6 ratio ≥4.
- Tantalum pentoxide (Ta2O5·nH2O) is successfully recovered after EDTA dissolution and neutralization.
- The process achieves high tantalum recovery efficiency with environmental advantages.

## Abstract

A new approach for the recovery of tantalum (Ta(v)) from alkaline solutions is presented, with the expected environmental benefits. This method is based on magnesium-induced precipitation to extract tantalum present as polyoxotantalates (POTas) from alkaline leachates. We obtained a tantalum precipitation yield of over 99% by introducing a Mg/Ta6 ratio of ≥4 into the solution. We show that Ta(v) ions, as hexatantalate species, precipitate in the presence of magnesium ions to form Mg4Ta6O19·xH2O crystalline phases with two different structures, with x = 16.1 or 24.4. The magnesium tantalate precipitate is then dissolved in ethylenediaminetetraacetic acid (EDTA) to release Mg(ii) in the form of an Mg(EDTA)2− complex. The final product, amorphous hydrated tantalum pentoxide (Ta2O5·nH2O), is obtained by neutralizing the Mg-EDTA-POTa solution to pH 7. After thorough washing with dilute acid and ultrapure water and calcination, tantalum pentoxide is obtained.

Extraction of soluble Ta(v) via precipitation with Mg(ii) and recovery as Ta2O5 solid.