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<p>Sulfadiazine (SDZ) is frequently detected in aquatic environments, posing potential ecological risks, which highlights the urgent need to develop efficient and sustainable removal technologies. In this study, a metal-free nitrogen-phosphorus co-doped biochar (N-P-BC) was synthesized using agricultural waste corn straw as raw material and employed to activate persulfate (PS) for SDZ degradation. The degradation performance, mechanistic insights, and environmental safety of the N-P-BC/PS system were systematically investigated. Under optimized conditions, the N-P-BC/PS system achieved 90.7% SDZ removal within 90&#xa0;min and maintained high degradation activity over a wide pH range of 3–9. Mechanistic studies revealed that singlet oxygen (<sup>1</sup>O<sub>2</sub>) was the predominant reactive species, and SDZ degradation primarily proceeded through the synergistic effect of electron transfer and energy transfer pathways. The system exhibited excellent degradation efficiency (&gt; 75%) in actual water matrices, retained 60.1% degradation efficiency after five consecutive cycles, and demonstrated broad-spectrum removal capability for various sulfonamide pollutants. Environmental matrix effect tests indicated that low concentrations of Cl<sup>−</sup> and Fe<sup>2+</sup> had negligible effects on the SDZ degradation mechanism; NO<sub>3</sub><sup>−</sup> exerted slight inhibitory effects on the degradation mechanism, whereas HCO<sub>3</sub><sup>−</sup> and humic acid showed significant inhibitory effects; the influence of Ca<sup>2+</sup> on the degradation process was negligible. Furthermore, twelve degradation intermediates were detected by high-performance liquid chromatography-tandem mass spectrometry, and four possible degradation pathways were proposed based on density functional theory calculations. Toxicity prediction results from T.E.S.T. software indicated that the predicted toxicity of degradation products was lower than that of the parent SDZ. This study constructs a metal-free N–P co-doped biochar based on agricultural waste, avoiding the risk of metal leaching, and provides new insights into the green design of modified biochar catalysts and their practical applications in water treatment.</p>

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Nitrogen-Phosphorus Co-Doped Biochar for Persulfate Activation in Sulfadiazine Degradation: Degradation Performance, Mechanism and Toxicity Assessment

  • 期刊论文

  • 发表日期：

    2026年4月7日

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  • Weiwei Yu,
  • Rongqi Liu,
  • Ting Ai,
  • Yufeng Mao,
  • Jiajie Li,
  • Lu Lv,
  • Dan Liu,
  • Yan Luo,
  • Wang Xin,
  • Man Luo,
  • Boyu Liu

摘要

Sulfadiazine (SDZ) is frequently detected in aquatic environments, posing potential ecological risks, which highlights the urgent need to develop efficient and sustainable removal technologies. In this study, a metal-free nitrogen-phosphorus co-doped biochar (N-P-BC) was synthesized using agricultural waste corn straw as raw material and employed to activate persulfate (PS) for SDZ degradation. The degradation performance, mechanistic insights, and environmental safety of the N-P-BC/PS system were systematically investigated. Under optimized conditions, the N-P-BC/PS system achieved 90.7% SDZ removal within 90 min and maintained high degradation activity over a wide pH range of 3–9. Mechanistic studies revealed that singlet oxygen (1O2) was the predominant reactive species, and SDZ degradation primarily proceeded through the synergistic effect of electron transfer and energy transfer pathways. The system exhibited excellent degradation efficiency (> 75%) in actual water matrices, retained 60.1% degradation efficiency after five consecutive cycles, and demonstrated broad-spectrum removal capability for various sulfonamide pollutants. Environmental matrix effect tests indicated that low concentrations of Cl− and Fe2+ had negligible effects on the SDZ degradation mechanism; NO3− exerted slight inhibitory effects on the degradation mechanism, whereas HCO3− and humic acid showed significant inhibitory effects; the influence of Ca2+ on the degradation process was negligible. Furthermore, twelve degradation intermediates were detected by high-performance liquid chromatography-tandem mass spectrometry, and four possible degradation pathways were proposed based on density functional theory calculations. Toxicity prediction results from T.E.S.T. software indicated that the predicted toxicity of degradation products was lower than that of the parent SDZ. This study constructs a metal-free N–P co-doped biochar based on agricultural waste, avoiding the risk of metal leaching, and provides new insights into the green design of modified biochar catalysts and their practical applications in water treatment.