The oxidation of waste resins catalyzed by zinc and the efficient immobilization of sulfur in KOH assisted Na2CO3-K2CO3 melt

Waste resins produced from nuclear facilities operation always contain organic sulfur and radioisotope 65 Zn, which pose a significant threat for the ecological environment. This study proposed comparative research for treating cation exchange resins doped with Zn 2+ (Zn-CERs) in Na 2 CO 3 -K 2 CO 3 and Na 2 CO 3 -K 2 CO 3 -KOH. The enhanced removal effect of sulfur and Zn 2+ by KOH addition was explored. The energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were carried out to investigate the element distribution and chemical states of C, O, S and Zn on Zn-CERs. The results of thermogravimetric analysis (TG) showed that the oxidation process of Zn-CERs was basically divided into three steps, and Zn 2+ acted as a catalyst for S-C destruction. The relatively mild reaction of Zn-CERs in Na 2 CO 3 -K 2 CO 3 -KOH largely avoids the escape of harmful gases (H 2 S and SO 2 ) caused by the overreaction. The participation of KOH could promote the sulfation of sulfides and sulfites, and the transformational SO 4 2− content reaches a maximum value (26.51 %) at 800 °C. When the temperatures above 700 °C, Zn 2+ and K + combines with SO 4 2− to form K 2 Zn 2 (SO 4 ) 3 . The proposed enhanced molten salt oxidation (MSO) system had excellent retention rates of Zn (99.56 %) and S (87.39 %) at 800 °C, which provides further technical references for the removal of organic sulfur and heavy metals.