Enhanced Chlortetracycline Removal by Iron Oxide-Modified Coffee Grounds Biochar

Chlortetracycline (CTC) is widely used in the livestock industry to promote animal growth and treat diseases. Effective actions should be taken to decrease the environmental risks associated with CTC-rich waste. Biochar produced by biomass waste shows great potential for organic contaminants removal by both adsorption and catalytic degradation. In this study, iron oxide-modified coffee grounds biochar (CGF) was prepared at different temperatures for enhanced CTC removal by adsorption and degradation. The main mechanism involved was found to be electrostatic interaction. In addition, pore diffusion, hydrogen bonds and π-π bonds also contributed to CTC adsorption. Maximum CTC adsorption capacity was 223.63 mg/g for CGF800 (CGF prepared at 800 o C pyrolysis). The free radical content of CGF600 (CFG prepared at 600 o C pyrolysis) was higher than CGF800, and there were no significant advantages in using biochar prepared at a higher temperature for persulfate activation. In addition, the structure of the CTC degradation products was analyzed by UPLC-MS, where the M/z values were 444, 273, and 154. Thus, pyrolysis of coffee grounds at higher temperatures increased CTC adsorption capacity, and CGF can indirectly assist in CTC degradation by persulfate activation