Synthesis of fly ash cenospheres-based hollow ABW zeolite for dye removal via the coupling of adsorption and photocatalysis

In this study, the powdery solid waste fly ash cenospheres (FACs) was used to synthesize zeolite nano-ABW, which maintained the initial hollow microsphere shape of the FACs. The synthetic nano-ABW zeolite was applied to remove direct fast bordeaux (DFB) dye. The coupling effects of adsorption and photocatalysis (adsorption/photocatalysis) were investigated in the degradation process. The removal rate was effectively increased from 1.4% of FACs to 72% of ABW, which may be due to the broad pore structure of synthesized hollow zeolite ABW, providing more active adsorption sites. Moreover, nano-Co3O4 semiconductor was supported on hollow ABW to further improve degradation efficiency. The results demonstrated that the removal of DFB over 6Co3O4/ABW zeolite was 66% under dark conditions, while enhanced to 90% under sunlight. Moreover, the removal rate of DFB only dropped by 4.5% after 5 cycles. It indicated that the Co3O4/ABW catalysts have high stability, and the photocatalysis enabled to degrade the dyes adsorbed on catalysts, thereby restoring the adsorption capacity of catalysts.