Plasma Assisted Aluminothermic Reduction of Cr and Fe Oxides from Chromium Bearing Waste

Safe disposal and management of chromium bearing wastes are challenging tasks. Recycling of Cr and Fe metals and production of value-added products from these wastes not only reduce the environmental pollution but are also a compelling necessity. The existing techniques to reduce Cr+6 to relatively non-toxic Cr+3compound/Cr metal either generate secondary waste, involve high cost or consume huge time. In this work, an attempt is made to reduce Fe and Cr metal oxides present in the chromium bearing waste by plasma assisted aluminothermic process. Chemical composition and leachability of chromium in the waste are analyzed. Aluminothermic reaction mixture is prepared with different weight ratios of waste to aluminium powder. Thermal stability of aluminothermic mixture and ignition temperature of the aluminothermic reaction are studied by TG and DSC analyses. Plasma assisted aluminothermic process is carried out in an argon environment at an atmospheric pressure. The products obtained from the waste are metallic mixture, slag and deposited/evaporated powder. Experiments are carried out at two different plasma powers and processing times. Slag and deposited powders do not contain Cr and Fe. The metallic fraction obtained contains Fe and Cr metals and AlFe3 alloy. This process can be a suitable method to treat chromium bearing waste effectively without producing toxic products.