The Use of Palmitoyl Hydroxyquinoline-Functionalized Amberlite XAD-2 Copolymer Resin for the Preconcentration and Speciation Analysis of Gallium(III)

Abstract

Gallium (Ga) is a valuable element in the electronics industry for manufacturing semiconductors and lasers. The processing of bauxite ores for the recovery of Ga, as well as high-level purification of the raw Ga product as required by electronic applications, necessitate effective speciation analysis of this element. For differentiating chemically important Ga(III) species, the Amberlite XAD-2 polystyrene-divinylbenzene copolymer was chloromethylated using AlCl3 as a catalyst, and later, 5-palmitoyl-8-hydroxyquinoline was covalently bound to this chloromethylated product via Friedel-Crafts reaction, resulting in the synthesis of a Ga-specific resin (Amberlite XAD-2-P·Ox). This resin has been shown to preconcentrate Ga selectively from basic aluminate solutions. The investigation of the effect of acidity on Ga recovery revealed that Ga was quantitatively retained on the resin between pH 3 and 7. The sorbed Ga could be eluted with 1 M HCl. A 100-mL volume of 2 ppm Ga showed 100% uptake by 10 g of resin using a flow rate of 1 mL/min. Here, all simple inorganic salts of Ga (e.g., Ga(III) nitrate, chloride, perchlorate), as well as the aquated Ga3+ (hexaaqua-complex) species, exhibit quantitative retention. On the other hand, oxalate-, tartrate-, citrate-, acetylacetonate, and EDTA complexes of gallium(III) were not retained by the resin under identical conditions. Thus, the synthesized chelating cation-exchanger showed selective affinity to simple inorganic Ga(III) salts, in a way acting as an ion-selective electrode for Ga3+ while excluding coordinatively saturated stable Ga-complexes. The developed ion-exchange procedure was used to separate gallium from arsenate in a commercial gallium arsenide sample, followed by Ga determination without interference.