Biosynthesis of stalk Biochar-nZVI and its catalytic reactivity in degradation of dyes by persulfate

Stalk Biochar (SBC) and Nanoscale zero-valent iron (nZVI) was coupled using biosynthesis method to form SBC-nZVI composite material. The couple of SBC and nZVI exhibits synergistic effect on improving catalytic activity for PS to get rid of dyes. The groups such as –OH and –COOH on the SBC can activate PS and nZVI has a better catalytic activity than SBC. SBC can enhance the dispersibility of nZV and protect it from oxidation to improve catalytic activity for PS and enhance electron conduct and transfer efficiency. Several important influencing factors on removal rate such as C: Fe mass ratio and inorganic anions were discussed in detail. Free radical quenching and electron spin resonance (ESR) analysis experiment confirm that superoxide radicals (O 2 ·− ) and hydroxyl radicals (·OH) played a role in the removal of contaminants but they were not the main radicals. Instead, sulfate radicals (SO 4 ·− ) was the main radical species in removal of contaminants. The SBC-nZVI composite material shows a good reusability, stability for store, and applicability for different type of dyes.