Upgrading Fast Pyrolysis Oil through Decarboxylation by Using Red Mud as Neutralizing Agent for Ketones Production and Iron Recovery

In this work, Red Mud, an alkaline solid waste from alumina production, was used as neutralizing agent to convert carboxylic acids in bio-oil into ketones. The total acidity of the bio-oil decreased significantly from 152.60 to 0.63 mg KOH/g, while the high heat value boosted from 17.25 to 29.57 MJ/kg. Meanwhile, the leachable alkalinity of Red Mud declined from 65.34 to 3.02 mg HCl/g, mitigating the harmfulness and perniciousness to the environment. Furthermore, characterizations of XRD, XPS and Fe-57 Mossbauer spectroscopy indicated that the weak magnetic iron species in Red Mud was completely transformed into stronger magnetic Fe3O4. With magnetic separation the iron recovery reached up to 91.96 % with iron grade of 65.83 %, which is up to the standard of steelmaking raw material. The findings in this research not only open avenue for valorization of bio-oil but also help explore the resourceful utilization of Red Mud.