Abstract:

Oxytetracycline hydrochloride is often used in the treatment of livestock and poultry diseases, however, it cannot be completely metabolized. The residual oxytetracycline hydrochloride entering water poses a threat to the health of water environment. Bivalent iron and bivalent manganese, as common transition metals, can usually activate sulfides to degrade organic pollutants. Its reaction conditions are mild and the operation is simple. However, the redox potential of single divalent iron and single divalent manganese is low, and the performance of activating sulfide is poor. In this experiment, Fe²⁺/Mn²⁺ coactivating Na₂SO₃ was used to degrade oxytetracycline hydrochloride in water. The effects of reagent dosage, pH, dissolved oxygen, chloride ion, carbonate ions and humic acid on the degradation of oxytetracycline hydrochloride in the Fe²⁺/Mn²⁺/Na₂SO₃ system were investigated. The oxidizing active substances in the Fe²⁺/Mn²⁺/Na₂SO₃ system were analyzed using pyrophosphate test, free radical quenching test and EPR experiment. The changes of functional groups and degradation intermediates of oxytetracycline hydrochloride were identified by UV-Vis spectroscopy, Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry, and the degradation pathway of oxytetracycline hydrochloride was inferred. The results showed that when the concentration ratio of Fe²⁺/Mn²⁺/Na₂SO₃ was 1∶4∶20 (the concentrations were 0.1, 0.4 and 2 mmol/L, respectively),the reaction time was 45 min and the pH was 9.0, removal efficiency and mineralization rate of oxytetracycline hydrochloride were the highest, and up to 94% and 49%, respectively. When dissolved oxygen decreased from 9 mg/L to 1.89 mg/L, removal efficiency of oxytetracycline hydrochloride decreased from 94% to 17%. Chlorine ions, humic acids and carbonate ions all had inhibitory effects on the degradation of oxytetracycline hydrochloride. Mn (Ⅲ) and \mathrm{S}{\mathrm{O}}_{\mathrm{4}}^{•-} were main active oxidants for the degradation of oxytetracycline hydrochloride, and the degradation underwent the processes of electron transfer, ring opening and acylation.

Key words: Fe²⁺/Mn²⁺/sulfite system, oxytetracycline hydrochloride, activation, radical, oxidation

摘要：

盐酸土霉素常被用于治疗畜禽疾病，但是它不能被畜禽完全代谢，残留的盐酸土霉素进入水体危害水环境的健康。铁锰作为常见的过渡金属，通常以二价态活化亚硫酸盐来降解有机污染物，反应条件温和、操作简单，但是单独的二价铁与二价锰氧化还原电势低，活化亚硫酸盐效果较差。本研究采用Fe²⁺/Mn²⁺共活化Na₂SO₃降解水中的盐酸土霉素，考察药剂用量、pH、溶解氧、氯离子、碳酸根及腐殖酸对Fe²⁺/Mn²⁺/Na₂SO₃体系降解盐酸土霉素的影响；通过焦磷酸盐实验、自由基淬灭实验和EPR实验分析Fe²⁺/Mn²⁺/Na₂SO₃体系中的活性物种；利用紫外可见光谱、傅里叶红外光谱、气相色谱-质谱联用仪识别盐酸土霉素的官能团及其降解中间产物的变化，推断盐酸土霉素的降解途径。结果表明：当Fe²⁺/Mn²⁺/Na₂SO₃浓度比为1∶4∶20（浓度分别为0.1、0.4和2 mmol/L）时，在反应45 min、pH为9.0条件下，盐酸土霉素的去除率和矿化率最高，分别达到94%和49%。随着溶解氧从9 mg/L下降至1.89 mg/L，盐酸土霉素去除率从94%下降至17%；氯离子、腐殖酸和碳酸根均对盐酸土霉素的降解产生抑制作用。Mn（Ⅲ）和\mathrm{S}{\mathrm{O}}_{\mathrm{4}}^{•-}是降解盐酸土霉素的主要活性氧化剂，盐酸土霉素的降解经过电子转移、开环与酰基化等过程。

关键词: Fe²⁺/Mn²⁺/Na₂SO₃体系, 盐酸土霉素, 活化, 自由基, 氧化