锰氧化物对土壤中三氯生的化学氧化

本文选取江西鹰潭红壤、云南金墩红壤和河南封丘潮土,研究了农田土壤中三氯生(TCS)在有无锰氧化物下的降解过程,考察锰氧化物浓度和有机酸种类及浓度对TCS降解率的影响,并通过高效液相–飞行时间质谱仪分析TCS的降解产物,探讨TCS在土壤中被活性锰氧化物氧化降解的过程。结果表明:锰氧化物在3种不同类型土壤中均具有不同程度的TCS去除能力,水土比4︰1条件下,5 g/L的MnO₂在酸性土壤(江西鹰潭红壤)中对TCS的氧化能力最强,云南金墩红壤土壤次之,这说明锰氧化物的氧化能力与土壤pH呈负相关性。同时TCS的降解率随着土壤中锰氧化物的浓度增加而增加,当土壤中锰氧化物的浓度升高到50 g/L时,TCS在8 h内的降解率达到81%,其一级反应动力学常数与锰氧化物浓度之间具有线性相关性。土壤中小分子有机酸能够影响TCS的降解效率,其中高浓度草酸和柠檬酸对TCS的降解具有明显抑制作用;而酒石酸则相反。此外,在反应过程中检测到TCS聚合形成的二聚体产物,并在此基础上提出了氧化转化路径。以上结果为理解TCS在土壤中的衰减和转化提供了新的视野,也为氯酚类污染场地修复提供了理论支撑。

Chemical Oxidation of Triclosan in Soil by Manganese Oxides

In this paper, red soil samples from Yingtan, Jiangxi and Jindun, Yunnan and alluvial soil samples from Fengqiu, Henan were collected to investigate the degradation of triclosan (TCS) in agricultural soils in the presence or absence of manganese oxides. The effects of manganese oxide concentration and organic acid types and concentration on TCS degradation were also investigated. The degradation products of TCS were analyzed by HPLC-TOF-MS to explore the oxidative degradation of TCS by reactive manganese oxides in soil. The results showed that MnO₂ could oxidize TCS in varying degrees in three different soil types at a water-soil ratio of 4:1, and the strongest oxidation capacity of TCS was observed in acidic soil (red soil from Yingtan, Jiangxi), followed by red soil from Jindun, Yunnan. It indicated that the oxidation capacity of MnO₂ was negatively correlated with soil pH. In addition, the degradation rate of TCS increased with the increasing concentration of manganese oxides in soil, and the degradation rate of TCS reached 81% within 8 h at 50 g/L MnO₂. There was a linear correlation between the kinetic constants of the first-order reaction and the concentrations of manganese oxides. The presence of small organic acids, such as oxalic and citric acids, significantly inhibited the degradation of TCS, but tartaric acid promoted it. In addition, the oxidative polymerizations pathway of TCS were proposed based on the detected dimers products. This study provided a new vision for understanding the attenuation and remediation of TCS in contaminated soil.