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<p>Iron-based catalysts have widely used in Fenton-like reactions, while the low redox cycling of Fe(III)/Fe(II) extremely limits their continuous performance. Hence, hydroxylamine (HA) is a green co-catalyst for iron-based Fenton-like catalysis. However, its synergistic effect on iron-containing waste in peroxymonosulfate (PMS) activation, and the related nitro-byproducts transformation and overall toxicity have never been explored. Herein, this work used waste heating pad (WHP) as the iron-based catalyst and HA as the co-catalyst to synergistically enhance the Fenton-like degradation of Rhodamine b (RhB) in water by activating PMS. The effects of various impact factors on RhB removal were systematically examined, and the associated mechanisms was elucidated. Besides, phenol (PhOH) was used as the probe substance to explore the species and toxicity evolution of nitro-byproducts. Results indicated that the HA/WHP/PMS system achieved the optimal RhB removal efficiency at the WHP dosage of 0.5 g/L, the HA concentration of 0.5 mmol/L, and the PMS concentration of 1.0 mmol/L, and exhibited wide pH applicability (3–9) and excellent degradation capabilities against different pollutants. In addition, WHP exhibited remarkable reusability and stability. The reactive oxygen species (ROS) in this system were proven by quenching experiments and electron paramagnetic resonance (EPR) spectra to be sulfate radicals (SO<sub>4</sub><sup>•−</sup>), hydroxyl radicals (<sup>•</sup>OH), and singlet oxygen (<sup>1</sup>O<sub>2</sub>), among which <sup>•</sup>OH was the most important ROS. Mechanism investigations indicated that the surface Fe(II) (≡Fe(II)) on WHP acted as dominant catalytic active sites, and HA facilitated the sustained PMS activation by reducing surface-bound Fe(III) (≡Fe(III)) on WHP back to ≡Fe(II). Moreover, the probe experiments demonstrated a small fraction of HA in the system of HA/WHP/PMS was converted into reactive nitrogen species (RNS), which then reacted with phenoxy radicals (PhO<sup>•</sup>) produced by PhOH oxidation to form nitrophenols by-products, and the reduced physiological toxicity was firstly evaluated. This work provides the theoretical reference value for the environmental objective of waste treatment by waste and offers insights into the related environmental impacts.</p>

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Hydroxylamine Co-Catalyzed Peroxymonosulfate Activation by Waste Heating Pad and its Transformation to Nitro-Byproducts: Performance, Mechanism, and Toxicity Evaluation

  • 期刊论文

  • 发表日期：

    2026年7月11日

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  • Min Zhang,
  • Leixin Wu,
  • Leilei Zheng,
  • Yiting Ma,
  • Nan Chen,
  • Ying Li,
  • Jing Guo,
  • Cheng Chen

摘要

Iron-based catalysts have widely used in Fenton-like reactions, while the low redox cycling of Fe(III)/Fe(II) extremely limits their continuous performance. Hence, hydroxylamine (HA) is a green co-catalyst for iron-based Fenton-like catalysis. However, its synergistic effect on iron-containing waste in peroxymonosulfate (PMS) activation, and the related nitro-byproducts transformation and overall toxicity have never been explored. Herein, this work used waste heating pad (WHP) as the iron-based catalyst and HA as the co-catalyst to synergistically enhance the Fenton-like degradation of Rhodamine b (RhB) in water by activating PMS. The effects of various impact factors on RhB removal were systematically examined, and the associated mechanisms was elucidated. Besides, phenol (PhOH) was used as the probe substance to explore the species and toxicity evolution of nitro-byproducts. Results indicated that the HA/WHP/PMS system achieved the optimal RhB removal efficiency at the WHP dosage of 0.5 g/L, the HA concentration of 0.5 mmol/L, and the PMS concentration of 1.0 mmol/L, and exhibited wide pH applicability (3–9) and excellent degradation capabilities against different pollutants. In addition, WHP exhibited remarkable reusability and stability. The reactive oxygen species (ROS) in this system were proven by quenching experiments and electron paramagnetic resonance (EPR) spectra to be sulfate radicals (SO4•−), hydroxyl radicals (•OH), and singlet oxygen (1O2), among which •OH was the most important ROS. Mechanism investigations indicated that the surface Fe(II) (≡Fe(II)) on WHP acted as dominant catalytic active sites, and HA facilitated the sustained PMS activation by reducing surface-bound Fe(III) (≡Fe(III)) on WHP back to ≡Fe(II). Moreover, the probe experiments demonstrated a small fraction of HA in the system of HA/WHP/PMS was converted into reactive nitrogen species (RNS), which then reacted with phenoxy radicals (PhO•) produced by PhOH oxidation to form nitrophenols by-products, and the reduced physiological toxicity was firstly evaluated. This work provides the theoretical reference value for the environmental objective of waste treatment by waste and offers insights into the related environmental impacts.