Co-pyrolysis route of chlorella sp. and bauxite tailings to fabricate metal-biochar as persulfate activator

Abstract

This study explored the feasibility of simultaneously producing synthetic gases and metal-biochar catalyst from co-pyrolysis of microalgae (chlorella vulgaris, CV) and industrial waste (bauxite tailings, BT). Co-pyrolysis was conducted in two different atmospheric conditions of N2 and CO2. Real-time syngas monitoring revealed the use of CO2 substantially enhanced CO production by expediting CO2-medicated thermal cracking of CV and its impact was further pronounced when BT was incorporated in the pyrolytic process. Characterization of produced metal-biochar revealed that metal-biochar have porous structure, Fe3O4 phase, and graphitic carbon layers with defective sites. The metal-biochar removed > 72% of 5 mg L−1 methyl orange within 60 min in the presence of 2 mM peroxydisulfate at 0.1 g L−1 biochar dose. Quenching test revealed the removal of methyl orange was mainly driven by singlet oxygen (1O2) generated by persulfate activation by metal-biochar. The reusability test indicated metal-biochar maintained>80% of its catalytic capability up to five repetitive reaction cycles of methyl orange removal. Collectively, co-pyrolysis of microalgae and industrial waste containing transition metals in CO2 condition can be a viable option to harvest energy resources from biomass wastes and to produce catalytic medium applicable to remove a wide range of redox active contaminants.