Figure 7

SEM–EDS morphology of pellets with different roasting times under roasting temperature of 1250 °C. (a): The roasting time is 15 min; (b): The roasting time is 20min; (c): The roasting time is 25 min; (d): The roasting time is 30 min.
SEM–EDS morphology of pellets with different roasting times under roasting temperature of 1250 °C. (a): The roasting time is 15 min; (b): The roasting time is 20min; (c): The roasting time is 25 min; (d): The roasting time is 30 min.