Deactivation diagnosis and in situ regeneration strategies for waste amidoxime chelating resins

The extraction of gallium using amidoxime chelating resin has demonstrated extensive industrial applications. However, repeated desorption cycles lead to resin deactivation, and untreated waste resins may pose environmental risks. This study conducted deactivation diagnosis on waste resin, characterizing its surface morphology and functional group distribution through FSEM, XPS, and FTIR analyses. The deactivated resin exhibited three key characteristics: Surface contamination by impurities, oxidation of amidoxime groups into carboxylic acids and hydroxamic acids, and occupation of Ga(III) adsorption sites by competing ions. To address these issues, a regeneration strategy combining ultrasonic cavitation for impurity removal with amidoximation of residual nitrile groups was proposed. Under the conditions of Ga(III) concentration 200 mg/L, pH 12, and liquid-solid ratio 100 mL/g, the regenerated resin demonstrated an adsorption capacity of 12.21 mg/g, which was 2.71 times that of new resin. The adsorption process of the regenerated resin conforms to the Langmuir isotherm. The theoretical maximum adsorption capacity of Ga(III) was calculated to be 34.78 mg/g under alkaline conditions. XPS analysis confirmed the critical role of oxygen-containing functional groups in Ga(III) adsorption. This research provides novel insights into resource utilization of the waste resin and demonstrates significant potential for Ga(III) extraction applications.