Synergy of adsorption-photocatalysis and enriched surface oxygen vacancies over lignin-biochar/Bi2MoO6 nanocomposites for organic pollutant removal and bamboo ECF bleaching effluent treatment

LC/Bi2MoO6 composites were successfully fabricated and applied to the effective degradation of methylene blue (MB) under visible light illumination. The composition, morphology and photoelectrochemical properties of prepared samples were characterized by various techniques. EPR analysis reveals that the density of surface oxygen vacancies was enhanced after lignin-biochar addition. Under optimal conditions, the degradation effi-ciency of MB over LC/Bi2MoO6 was 95.34 % at 1 h under visible light irradiation, and the reaction rate constant (k) was 18.96 folds higher than that of pristine Bi2MoO6. The enhanced photocatalytic performance of LC/ Bi2MoO6 was due to the synergistic effect between adsorption-photocatalysis and enriched surface oxygen va-cancies, which greatly promotes the separation of photogenerated charge carriers. Moreover, the MB degradation removal with LC/Bi2MoO6 decreased by 3.84 % at 1 h under visible light irradiation after four cycles, illustrating excellent stability and reusability in the photocatalytic recycling process. Notably, the bandgap of Bi2MoO6 decreased from 2.66 eV to 2.26 eV with the addition of lignin-biochar. Radical capture experiment and ESR characterization demonstrate that center dot OH radicals were the main active radical in the photocatalytic process, which increases the radical concentration during the combination of lignin-biochar. Furthermore, the LC/Bi2MoO6 composites were also applied to the degradation of bamboo ECF bleaching effluent, with a higher CODCr and AOX removal of 75.72 % and 69.64 %, respectively. Herein, this work provides a novel insight for constructing economic and efficient photocatalysts for wastewater remediation and biomass utilization.