Plasma Assisted Aluminothermic Reduction of Cr and Fe Oxides from Chromium Bearing Waste
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Plasma Assisted Aluminothermic Reduction of Cr and Fe Oxides from Chromium Bearing Waste R. Saravanakumar1 · K. Ramachandran1 · P. V. A. Padmanabhan2 Received: 21 December 2019 / Accepted: 4 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract 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 r+3compound/Cr metal either generate techniques to reduce C r+6 to relatively non-toxic C 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 A lFe3 alloy. This process can be a suitable method to treat chromium bearing waste effectively without producing toxic products. Keywords Cr bearing waste · Thermal plasma · Aluminothermic reaction · Transferred arc · Metal · Recovery · TCLP
Introduction The wastes produced by chemical and leather/tanning industries contain large amount of iron and aluminium as well as significant amount of chromium and magnesium. These wastes have been generated in several thousand tons every year and land filled/discarded without effective treatment. The improper disposal and mismanagement of chromium containing wastes cause serious issues to all forms of life. The diffusion of the hexavalent chromium (Cr6+) present in the land filled waste into the soil and ground water * K. Ramachandran [email protected] 1
Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu, India
2
Power Beam Society of India, Mumbai, India
13
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Plasma Chemistry and Plasma Processing
is of major concern. Heavy environmental pollution due to Cr6+ is also associated with extraction, production and use of chromium concentrate in developing countries. Various extraction and recovery processes like bio-metallurgy, hydrometallurgy and pyrometallurgy have been developed to convert hazardous Cr6+ into either Cr3+ or Cr metal. Bio-metallurgy [1] is an adsorption-based process and biosorbents are employed in this method to treat chromium contaminated waste water. Hydrometallurgy [2] is a ch
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