Performance and mechanism of tea waste biochar in enhancing the removal of tetracycline by peroxodisulfate.

In this work, tea waste biochar was prepared and used to activate peroxodisulfate (PDS) for the removal of tetracycline (TC) efficiently. And SEM, XRD, Raman, and FTIR were used to characterize the biochar. The effects of reaction conditions including initial pH, biochar dosage, and PDS concentration on the removal of TC were explored, and the result showed that compared with the biochar prepared at 400 °C and 500 °C, the biochar pyrolyzed at 600 °C (TBC600) had the highest TC removal performance due to its higher sp hybrid carbon content, richer defective structure, and stronger electron deliverability. Under the optimal dosage of PDS (4 mM) and TBC600 (0.8 g L), the removal efficiency of TC (10 mg L) reached 81.65%. After four cycles of TBC600, the removal rate could still reach 75.51%, indicating that TBC600 has excellent stability. In addition, quenching experiments and electron paramagnetic resonance (EPR) verified that the active oxygen including SO·, ·OH, O·, and singlet oxygen (O) was involved, among which O and OH were the main active substance in the TC removal. Therefore, this work provided a green and efficient persulfate activator and a method for recycling tea waste.