Facile preparation of a novel modified biochar-based supramolecular self-assembled g-C3N4 for enhanced visible light photocatalytic degradation of phenanthrene

The rational design of a novel and environmentally friendly photocatalytic composite for persistent pollutant removal, energy production and catalytic applications have attracted widespread interest. In this study, the new composite composed of KOH-modified biochar and g-C3N4 with different morphologies was successfully prepared with facile supramolecular self-assembly and thermal poly-condensation method. The characterization results of the as-prepared composites suggested that KOH-modified biochar had been well combined with g-C3N4 with different morphologies. These synthesized catalysts were used to degrade phenanthrene under visible light radiation. A-BC/g-C3N4-D performed best and removed 76.72% phenanthrene. Its first-order reaction rate constant was 0.355 h-1, which was 3.7 times higher than that of g-C3N4. A-BC/g-C3N4-D still exhibited a high photocatalytic activity after four cycles. Radical quenching results showed that superoxide radical (·O2-), hydroxyl radical (·OH) and hole (h+) could be used as active species in the redox reaction with phenanthrene. Based on the exploration results of gas chromatography-mass spectrometer (GC-MS), a possible reaction pathway of phenanthrene degradation was also proposed. This study provides a novel strategy for fabricating various high-performance photocatalysts and the removal of persistent organic pollutants.