Microwave-enhanced roasting of copper sulfide concentrate in the presence of CaCO3

The microwave irradiation is used to the oxidative roasting of copper sulfide concentrate in the presence of CaCO3 with the aim of eliminating sulfur dioxide emissions and accelerating roasting process. The calcine obtained is leached with NH3–(NH4)2CO3 solution for the recovery of copper. It is shown that the copper extractions from the calcine roasted with microwave heating are as high as 90–96.6%, while those with conventional heating are only 71–77.4%. The sulfur retention is greater than 96% for both the microwave and conventional heating. The reaction rates of the roasting process increased 3.97–17.15 times when using microwaves instead of conventional heating. The phase changes and reaction mechanism of the roasting process are also investigated with X-ray diffraction and thermal analysis.