AbstractKraft black liquor/green liquor was continuously recirculated in a column (diameter 100 mm, height 450 mm) packed with 16‐mm polypropylene Pall rings countercurrent to a gas stream containing N2 and O2 (O2–3.7%). The concentration of sulphide in the green liquor was not affected by oxygen in the gas; the latter, however, completely oxidised the sulphide in kraft black liquor over an 8 h recirculation period.