Novel reductive extraction process to convert the bio-oil aqueous acid fraction into fuels with the recovery of iron from wastes

Highlights

• Bio-oil aqueous acid fraction efficiently extracts iron of the red mud waste.

• Fe_extracted/aqueous fraction is converted into Fe/C composites valuable for the steel industry.

• The organics are decomposed to a potential fuel gas mixture consisting of H₂/hydrocarbon.

Abstract

In this work, bio-oil waste AAF (aqueous acid fraction) was used to recover iron from red mud (RM) waste by a reductive extraction process. In this process, extraction of iron from RM with AAF is followed by thermal treatment of AAF-Fe_extracted mixture, leading to the reduction of the Fe_extracted with the production of Fe/C composites, a valuable feedstock for the steel industry, and a gas fuel fraction. Analyses by IR, UV–vis, ESI-MS, CHN, potentiometric titration, TG, TG-MS, TOC and ¹H NMR showed AAF can efficiently extract Fe³⁺ present in RM waste. After extraction, the mixture AAF-Fe_extracted was treated at 400, 600 and 800 °C to decompose mainly into two fractions: solid (30–40 wt%) and gas (60–70 wt%). Mössbauer and XRD analyses of the solid fraction showed the presence of reduced iron phases, e.g. Fe²⁺, Fe⁰ and iron carbide, with 76% of carbon. TG-MS analyses of gas fraction showed the production of H₂ (58 mol%), C₁–C₄ (19 mol%) and CO_x (23 mol%), with potential application as a fuel.