*Article* **N-Rich Algal Sludge Biochar for Peroxymonosulfate Activation toward Sulfadiazine Removal**

**Chao Liu 1,2,†, Zhenxiang Chen 3,†, Ruiqin Kang <sup>1</sup> , Jing Wang <sup>1</sup> , Qingwei Lu <sup>1</sup> , Tao Wang <sup>1</sup> , Dayong Tian 1,\*, Ying Xu 2,\*, Zhan Wang <sup>4</sup> and Huiping Ding <sup>5</sup>**

	- Jiangsu Xingzhou Ecological Environment Technology Co., Ltd., Nanjing 210004, China

**Abstract:** The fabrication of a green, high activity and low-cost carbon-based catalyst capable of activating new oxidant (peroxymonosulfate, PMS) for contaminants abatement is needed. In this research, we prepared novel N-doped biochars via one-step pyrolysis of algal sludge without external nitrogen sources. The obtained ASBC800 possessed the largest specific surface area (SBET = 145.596 m<sup>2</sup> g −1 ) and thus it displayed the best catalytic performance, as revealed by the effective elimination of sulfadiazine (SDZ, >95% within 70 min) with 0.2 g L−<sup>1</sup> ASBC800 and 0.5 mM PMS. Both radical species (e.g., SO<sup>4</sup> •−, and •OH), and nonradical regime (1O<sup>2</sup> and electron-transfer) contributed to SDZ oxidation, in which ASBC800 played essential roles in activating PMS, accumulating SDZ, and regulating electron shuttle from SDZ to ASBC800-PMS\*. Overall, this work not only provides a novel strategy for the synthesis of N-rich and cost-effective biochar but also promotes the development and application of carbon-based functional materials in environmental remediation.

**Keywords:** peroxymonosulfate; pre-adsorption; oxidation; electron-transfer; N doping
