Soybean straw biochar activating peroxydisulfate to simultaneously eliminate tetracycline and tetracycline resistance bacteria: Insights on the mechanism

Tetracycline (TC) has been frequently detected in various environments, thus promoting the occurrence of resistance in bacterial populations. In this study, a suite of soybean straw biochars (SSBs) were fabricated under different pyrolysis temperatures (600-1000 degrees C), which were utilized as peroxydisulfate (PS) activators for TC degradation and TC resistant Escherichia coli (E. coli) disinfection. The purification effect of SSBs/PS systems manifested obvious positive dependence on pyrolysis temperature of SSBs with SSB1000/PS system obtained the superior TC degradation, E. coli disinfection and coexisting TC and E. coli elimination capacity. The leakage of intracellular DNA and the degradation of total DNA and extracellular DNA was revealed no matter in alone E. coli or combined pollution which can also be supported by the gradual ruptured bacterial morphology and attenuated internal components. It can be found that TC adsorption in SSBs played a significant role on TC degradation, while the electrostatic repulsion always existed between E. coli and SSB1000. Furthermore, a battery of solid evidences collectively demonstrated the significant different purification mechanism of TC and E. coli. The TC degradation was achieved dominantly by surface-bound radicals, while bactericidal activity should be attributed to free SO4 center dot- in bulk solutions. In contrast to other SSBs, the largest mesopore volumes, highest C=O content, lowest interfacial charge transfer resistance and strongest electron donating capacity explained the outperformed catalytic performance of SSB1000.

Automated summary

Tetracycline has been detected in various environments, leading to the development of resistance in bacterial populations. This study fabricated soybean straw biochars (SSBs) at different pyrolysis temperatures and used them as activators for the degradation of tetracycline and disinfection of tetracycline-resistant Escherichia coli. The results showed that the purification effect of SSBs depended on the pyrolysis temperature, with SSB1000/PS system exhibiting superior degradation and disinfection capabilities. The purification mechanisms of tetracycline and Escherichia coli were found to be different, with tetracycline degradation mainly relying on surface-bound radicals and bactericidal activity attributed to free SO4 center dot- in bulk solutions. The catalytic performance of SSB1000 was attributed to its unique characteristics, such as large mesopore volumes, high C=O content, low interfacial charge transfer resistance, and strong electron donating capacity.