Elimination of sulfadiazine and its metabolite from hydrolyzed urine by biochar activated periodate process: Lower environmental risk compared with CoFe2O4/peroxymonosulfate process

Source-separation and treatment of urine are recognized as promising strategies to recover nutrients, as well as reduce the stress of terminal wastewater treatment plants. As a ubiquitous constituent of urine, NH 4 + has been demonstrated to induce the generation of nitro-byproducts in sulfate radical (SO 4 •− ) dominated oxidation processes. In this work, wheat straw derived biochar (BC X , X represents the pyrolysis temperature) was prepared and adopted to eliminate sulfadiazine (SDZ) and its main human metabolite N 4 -acetyl-sulfadiazine (NSDZ) from hydrolyzed urine by coupling with periodate (PI). Specifically, BC 800 /PI process achieved excellent SDZ (0.190 h −1 ) abatement, which was more efficient than NSDZ. HCO 3 − and NH 4 + significantly inhibited the removal processes whilst Cl − showed neglected effect. Both in situ and ex situ analysis excluded the dominant role of •OH, 1 O 2 , O 2 •– and/or •IO 3 . Instead, electron-transfer regime driven by the high potential BC 800 -PI* complexes played a significant role. Interestingly, BC 800 /PI and CoFe 2 O 4 /peroxymonosulfate (PMS) (a typical SO 4 •− -dominated oxidation process) exhibited comparable removal efficiencies towards SDZ. Four nitro-byproducts were identified in CoFe 2 O 4 /PMS process but negligible in BC 800 /PI process during SDZ treatment, revealing the merit of BC 800 /PI process. Eventually, the toxicity prediction and bactericidal experiments further implied that BC 800 /PI process was eco-friendly. This study proposed a heterogeneous BC 800 /PI process for the treatment of source-separated urine and comprehensively demonstrated the advantages of its low costs and environmental risk.