Natural substance-mediated synthesis for biochar-supported nanoscale zero-valent iron enhanced the performance of the catalytic process

Nanoscale zero-valent iron (nZVI) has gained increasing attention as a heterogeneous catalyst. However, problems such as aggregation, oxidation, or iron leaching limit its application. An appropriate dispersant and carrier may help solve the problems. Natural substances and their waste have been investigated as potential dispersants and carriers. Chinese herbal medicine residue is a promising raw material for this purpose. Here, black bean peel, a natural substance, was used as a dispersant and stabilizer, and biochar from chaga mushroom residue was used as a support for the first time to synthesize a zero-valent iron composite (B-nZVI-BC). X-ray diffraction (XRD) and electron spin resonance (ESR) studies confirm that the natural extracts prevented the agglomeration and oxidation of nZVI and promoted hydroxyl radical (·OH) generation. The experimental results showed that the B-nZVI-BC (2:1) + H2O2 system reduced Fe leaching to 0.66 mg/L. The synergistic effects of natural extracts, biochar (BC), and nZVI activated H2O2 for tetracycline (TC) removal and increased the removal from 67.56% to 90.07%. New insights were provided into the green synthesis and regeneration of nZVI, offering a promising solution for its practical application.