An innovative slag cleaning and gypsum wastes treatment technique was presented.
The results verified the feasibility and reliability of the innovative technique.
CaSO<sub>4sub> can efficiently and preferentially sulfurize Cu<sub>2sub>O and CoO into sulphide.
92.04% Cu and 95.62% Co lost in initial slag can be selectively recovered.
Ca-rich and Fe-poor slag property was more beneficial to minimize Cu and Co losses.