A new strategy for germanium adsorption on activated carbon by complex formation

Abstract

Considering that germanium species in solution are scarcely adsorbed on activated carbon, the objective of this research was to develop a method for its recovery from diluted aqueous solution by activated carbons. This process is based on the use of an organic compound as a ligand in order to form an adsorbable germanium complex; afterwards activated carbon is used as sorbent. Two different commercial activated carbons, showing similar textural properties but different surface chemistry, were used as sorbents. From the obtained results, it can be said that the use of activated carbon for the adsorption of the Ge complex is a simple, rapid and efficient method, allowing its concentration on the carbon surface and its subsequent desorption – and hence recovery of the Ge. The results also show that: (i) carbon surface functionalities have a notable effect on the adsorption of the Ge complex; (ii) initial pH and the ionic strength have a noticeable importance on the adsorption process. The recovery of germanium and the reuse of the spent activated carbon have been studied. Thus, after adsorption, activated carbons were submitted to a desorption process, based on the modification of the pH for the destruction of the Ge complex at acid pH. It has been demonstrated that after the desorption process the activated carbon can be reused in several adsorption–desorption cycles although with a slight decrease in its adsorption capacity after each cycle. Based on the suitability of the activated carbons to remove germanium and on its easy desorbing process, this is also a promising method to concentrate Ge from dilute solutions. Preliminary studies for aqueous metal ions mixtures have demonstrated that this method is selective for Ge recovery when other elements are present in the initial solution.