Cow Manure Pellet Biochar: Leaching of Cu(II) and Its Corresponding Influences on Tetracycline Adsorption

Valorizing heavy metal–contaminated livestock manure into biochar and thus used for decontaminating antibiotics in farm wastewater is an agricultural circular economy strategy concept. Aiming to illustrate the dynamic and underlying mechanism of Cu(II) leaching from cow manure pellet biochar and its influences on the biochar’s ability to adsorb tetracycline, cow manure–derived pellet biochar with a pyrolysis temperature of 800 ℃ was used in this study. A series of heavy metal leaching experiments in Britton-Robinson (BR) buffer and tetracycline (TC) standard aqueous solution and tetracycline adsorption experiments including isothermal adsorption and kinetics adsorption were conducted. Conventional lab wet chemical analysis, quantum chemistry simulation, and micro-CT technique were employed to fully characterize the resulting samples. The results show that the leaching behaviors of Cu(II) from cow manure pellet biochar were different in BR system and TC system. As indicated by the quantum chemistry simulation, leached Cu(II) participated in the TC adsorption process of biochar by forming tetracycline-copper complexes and accelerated the adsorption rate of TC on biochar. The revealed interaction between heavy metal and antibiotic during the adsorption process will be significant to help a more comprehensive interpretation of the complex adsorption mechanism of biochar. This study provides a more comprehensive understanding of the intricate mechanism of organic pollutant adsorption on biochar.