Abstract:

Enrofloxacin (ENR) belongs to the fluoroquinolone class of antibiotics, characterized by strong stability, difficult degradation, and easy accumulation. It is commonly used in aquaculture and livestock farming. Although its overall concentration in the environment is low, long-term exposure to low doses may pose significant risks to human health and the ecological environment. The removal of ENR from water is achieved by utilizing carbon spheres (CS) loaded with nano zero-valent iron (nZVI) to activate persulfate (PS). Carbon spheres loaded with nano zero-valent iron (Fe@C) were prepared using a two-step carbon thermal reduction method. Single-factor experiments were conducted to investigate the effects of Fe@C dosage, PS concentration, initial ENR concentration and pH on ENR degradation. The reaction mechanism and degradation pathway of ENR by Fe@C activated PS were speculated through the analysis of free radicals and degradation products. The results indicated that the degradation of ENR followed a pseudo-first-order kinetics. Under the conditions of 25 ℃, Fe@C dosage of 0.3 g∙L⁻¹, PS concentration of 1 mmol∙L⁻¹, initial ENR mass concentration of 10 mg∙L⁻¹, and pH of 3, the highest ENR degradation rate reached 98.6%. The degradation rate of ENR decreased with increasing concentrations of humic acid (HA), ammonia nitrogen (NH₃-N), and bicarbonate ions (HCO₃⁻). The chloride ions (Cl⁻) had a slight promoting effect on the degradation of ENR at low concentrations and an inhibitory effect at high concentrations. Free radical quenching experiments indicated that SO₄⁻∙ was the main free radical involved in ENR degradation. Based on the degradation products of ENR, it was speculated that the cleavage of the piperazine ring, decomposition of the quinolone ring, and defluorination were the main degradation pathways of ENR. The Fe@C activated persulfate advanced oxidation process can serve as an efficient technology for removing ENR from water.

Key words: enrofloxacin (ENR), carbon sphere-supported nano zero-valent iron, persulfate, degradation pathways, activation, degradation kinetics

摘要：

恩诺沙星（ENR）属于氟喹诺酮类抗生素，具有稳定性强、难分解、易富集等特性，常用于水产养殖、畜禽养殖等，其在环境中总体浓度较低，但长期低剂量暴露可能对人体健康和生态环境带来极大风险。采用碳球（CS）负载纳米零价铁（nZVI）活化过硫酸盐（PS）去除水体中的ENR。应用两步碳热还原法制备了碳球负载纳米零价铁（Fe@C），采用单因素实验研究了Fe@C投加量、PS浓度、ENR初始浓度和pH值对ENR降解的影响及降解动力学，通过自由基及降解产物分析推测了Fe@C活化PS降解ENR的反应机制与降解路径。结果表明，ENR的降解符合准一级动力学，在温度为25 ℃、Fe@C投加量为0.3 g∙L⁻¹、PS浓度为1 mmol∙L⁻¹、ENR初始质量浓度为10 mg∙L⁻¹、pH值为3的条件下，ENR降解率最高达98.6%。ENR降解率随着腐植酸（HA）、氨氮（NH₃-N）、碳酸氢根离子（HCO₃⁻）浓度的升高而降低。氯离子（Cl⁻）在低浓度时对ENR的降解有微弱的促进作用，高浓度时有抑制作用。自由基淬灭实验表明SO₄⁻∙是ENR降解的主要自由基。根据ENR的降解产物，推测哌嗪环的裂解、喹诺酮环的分解及脱氟为ENR主要降解途径。碳球负载纳米零价铁活化PS高级氧化工艺可作为一种高效去除水中ENR的工艺。

关键词: 恩诺沙星, 碳球负载纳米零价铁, 过硫酸盐, 降解途径, 活化, 降解动力学