Ammonium persulfate activated by ultrasound for sulfur-containing ion purification

Ammonium persulfate has been proven to be effective in purifying thiosulfate (S 2 O 3 2− ) and sulfite (SO 3 2− ) impurities in desulfurization solutions. However, the sole use of ammonium persulfate as an oxidant faces the challenge of high oxidant consumption. In this study, a novel approach was proposed to enhance the oxidation efficiency of ammonium persulfate on sulfur-containing ions through ultrasonic activation. The results indicate that this technology has the advantages of high purification efficiency and low usage of ammonium persulfate. Specifically, the concentrations of S 2 O 3 2− and SO 3 2− decreased from 16.26 g/L and 38.30 g/L to 1.09 g/L and 8.89 g/L, respectively, meeting the actual production requirements; and the usage of ammonium persulfate could be reduced by 10–30 g per liter of solution compared with the case of ammonium persulfate alone. The introduction of ultrasound increased the generation of free radicals (SO 4 · − and ·OH), enhancing their oxidative capacity. The contribution of free radicals to the oxidation of S₂O₃ 2− and SO₃ 2− increased from 11.1 % and 9.8 % to 50.0 % and 25.8 %, respectively. This study reveals that the ultrasonic activated ammonium persulfate is expected to achieve efficient purification of the desulfurization mother liquor and reduce the addition of ammonium persulfate.