Recovery Nickel-Ferrous Compound from Nickel-Bearing Secondary Resources

The stainless steel pickling sludge contained valuable metals such as Fe, Cr, and Ni and was a second Ni-bearing resource. It was essential to explore an economical technology for recovery metals from the low grade pickling sludge. The method of carbon thermal reduction–magnetic separation process was proposed to not only recover Fe, Cr, and Ni from the stainless steel sludge, but also dispose waste environmental friendly. The weight variety and phases change were characterized with TG-DSC and XRD. The influence of reduction temperature, the ratio of C/O (carbon/oxygen), the reaction time, and addition of pickling sludge were investigated. The experimental results showed that the best reduction condition was at temperature 1350 °C, with 1.0 C/O ratio. The recovery rate of Ni and Fe was reached up to 97.86 and 96.07%, respectively, under this condition. Meanwhile, the contents of Fe, Ni, and Cr of the tailings were 4.04, 0.06, and 0.09%.