Recovery of Gallium from Aqueous Solution through Preconcentration by Adsorption/Desorption on Disordered Mesoporous Carbon

Abstract

This work studies gallium preconcentration by means of an adsorption/desorption process using two mesoporous activated carbons synthesized by the replica method as adsorbents. The adsorption results indicate that both carbons can remove 90% of gallium from aqueous solution. Increasing the adsorbent dose favors gallium adsorption and makes the adsorption process strongly pH dependent. However, the most outstanding conclusion is related to the gallium recovery: by using a HF solution as desorbing agent (the same as employed in the adsorbents¿ synthesis, in line with circular economy principles), it is possible to regenerate the adsorbent as well as recover 82% of the gallium previously retained. Additionally, the desorption enables sevenfold preconcentration of gallium ions, up to 250 ppm, by reducing the volume of the acidic solution eightfold. This enables further recovery by means of refning processes such as extraction.