Enhanced sulfamethazine degradation via peroxydisulfate activation by biochar-supported nano zero-valent iron-copper: The key role of Fe(IV) and electron transfer induced by doped Cu

The effective treatment of antibiotic wastewater is necessary to the cleaner production of many industries. Herein, a novel catalyst of biochar-supported nano zero-valent iron-copper (nZVI/Cu@BC) was synthesized, which showed more efficient activation of peroxydisulfate (PDS) for sulfamethazine (SMZ) degradation than the catalyst before nZVC doping, from 77.81% to 96.44%. And it was found to be mainly owing to the role of Fe(IV) and electron transfer induced by doped Cu. Specifically speaking, the doped Cu caused over an order of magnitude increase in Fe(IV) formation from 1.84×10−10 M to 4.75 × 10−9 M. And the more significant electron transfer between nZVI/Cu@BC, PDS and SMZ was confirmed by series electrochemical tests. In contrast, the formation of SO4·- and OH was still at a low concentration, playing a small role. The different activation mechanisms were identified to be that doped Cu provided Cu(Ⅰ)/Cu(Ⅱ) cycle to accelerate Fe(Ⅱ)/Fe(Ⅲ) cycle for enhanced PDS activation. Besides, the Fe0/Cu0 co-active sites appeared on the material surface after nZVC doping, exhibiting a stronger interaction with PDS. Therefore, nZVI/Cu@BC performed better under a wider pH range as well as complex water environment, and eliminated the toxicity of SMZ due to the nonradical-dominant process. This work provides a new insight into the rational design of nano zero-valent metals for efficient wastewater treatment to ensure cleaner production.