Visible light photocatalytic degradation and pretreatment of lignin using magnetic graphitic carbon nitride for enhancing methane production in anaerobic digestion

The objective of this study was to investigate photocatalytic lignin degradation utilizing magnetically removable Fe3O4@g-C3N4 under visible light irradiation. Optimum conditions for lignin degradation by Fe3O4@g-C3N4 were determined. The results showed that Fe3O4@g-C3N4 can photocatalytically decompose lignin up to 90% at pH 7 after 3 h of visible light irradiation, and optimum catalyst loading in this study was 2.5 g/L. The synthesized photocatalyst exhibited stable photocatalytic activity after seven cycles. Anaerobic digestion of the photocatalytic degraded lignin for methane and biogas production was assessed with a novel approach for anaerobic digestion. In the proposed method, anaerobic digestion was conducted in total organic carbon vials with a 4 mL sample, without the need for gas collection. The key finding of this study was that the treated lignin sample outperformed the untreated lignin in terms of increased methane production by 30%.