Germanium(IV) Adsorption by Inorganic Oxides Modified Layer-by-Layer with Polyhexamethylene Guanidine and Tiron

The laws of germanium(IV) adsorption by adsorbents based on alumina or silica layer-by-layer modified with polyhexamethylene guanidine (PHMG) and tiron (Al 2 O 3 –PHMG–tiron and SiO 2 –PHMG–tiron) were studied. The effects of Lewis acid sites of alumina on the anchorage of modifier reagents and on germanium(IV) recovery are discussed. In contrast to silica, tiron is anchored to unmodified alumina. Germanium(IV) adsorption on the Al 2 O 3 –PHMG–tiron adsorbent is both due to interaction with tiron and due to interaction with the alumina surface, while on SiO 2 –PHMG–tiron, adsorption is solely due to complexation with the reagent followed by the formation of surface compounds of the Ge : tiron = 1 : 3 stoichiometry. Quantitative (99%) recovery of germanium(IV) by the SiO 2 –PHMG–tiron adsorbent is achieved in a pH range of 2.0–6.5, and by the Al 2 O 3 –PHMG–tiron adsorbent in the range from 0.5 M HCl to pH 8.5.