Efficient activation of peroxydisulfate by modified red mud biochar derived from waste corn straw for levofloxacin degradation: Efficiencies and mechanisms

As using iron-based materials and biomass to prepare effective catalyst has emerged as a hit trend in persulfate-based advanced oxidation processes (PS-AOPs), the problems associated with excessive chemical consumption, costly expenses, and complex synthetic processes have become more urgent to be addressed. Therefore, by using red mud (RM) and corn straw (CS), a modified red mud biochar catalyst (MRBC) was synthesized through acid pretreatment and pyrolysis (700 °C). MRBC presented excellently in peroxydisulfate (PDS) activation to degrade levofloxacin (LFX). Under the experimental setup involving 8 mM PDS, 10 mg L−1 LFX, and 1.6 g L−1 MRBC, 88.59% of LFX was effectively eliminated within 30 min with an exceedingly low Fe leaching rate of 0.049 mg L−1. Furthermore, even after four cycles of reuse, it was able to sustain a remarkable 61.63% efficiency in LFX degradation. The characterization of catalysts demonstrated the synergistic effect of RM and biomass could be responsible for the excellent catalytic properties of MRBC. The results of quenching experiment and the presence of DMPOX in EPR demonstrated radical pathway mainly contributed to the LFX degradation in MRBC/PDS system. Overall, PDS was activated by the active sites of MRBC such as Fe (II) and persistent free radicals (PFRs) to generate a large amount of SO4•− and •OH to remove LFX. This work investigated the synergy of RM and biomass in catalyst preparation, deepened the insights into the application of RM catalysts in PS-AOPs to degrade antibiotic, and contributed greatly to the recovery of waste resources.