Effective removal of hydrogen sulfide using Mn-based recovered oxides from recycled batteries

Abstract The use of clean and environmentally friendly renewable energy as well as the minimization of waste disposal are fundamental aspects to be considered nowadays in a circular economy approach. In this way, the development of efficient systems for sulfur removal in biomass and waste gasification is of key relevance and the use of recycled materials will provide an opportunity to combine the reduction of waste‘s production and the application of circular economy principles. Sorbents from waste powder of recycled batteries have been prepared at laboratory scale. Subsequently, their potential application to syngas cleaning is evaluated specifically for H2S removal. Lab-scale tests at 400°C, 10 bar and space velocity of 3500 h−1 were carried out using first a simplified gas mixture of 0.9% H2S in N2 and then a more complex one consisting of 20% H2, 40% CO and 0.45% H2S/N2 to investigate the effect of reducing components, CO and H2 co-existing with H2S in any syngas. Sorbent utilization values as high as 80% (w/w, %) were obtained when tested under realistic syngas composition. XRF, XRD, XPS, TEM and textural characterization results of fresh and sulfided samples showed that those materials with higher Mn contents showed higher H2S removal capacity although the Mn/Zn ratio demonstrated to play a crucial role in their selectivity to form sulfides. Additionally, plausible mechanisms for H2S removal are discussed where the influence of composition, structure and morphology of the recovered binary metal oxides on sulfur removal efficiency is analysed.