8种磺酰脲类除草剂在腐植酸上的吸附作用与机理初探

Adsorption Behavior and Mechanism of Eight Sulfonylurea Herbicides on Humic Acid

利用室内实验方法,研究了甲磺隆、绿磺隆、甲嘧磺隆、烟嘧磺隆、吡嘧磺隆、氯嘧磺隆、苄嘧磺隆和噻磺隆等8种磺酰脲类除草剂在腐植酸上的吸附行为,利用批量平衡法测定了它们的吸附等温线,评价了pH值和离子强度等因素对吸附的影响,同时借助傅里叶变换红外光谱仪(FT-IR)手段对其吸附机理进行了初步探讨。结果表明,腐植酸对8种磺酰脲除草剂的吸附作用较强,其吸附强弱依次为氯嘧磺隆>苄嘧磺隆>绿磺隆>噻磺隆>甲磺隆>吡嘧磺隆>烟嘧磺隆>甲嘧磺隆。吸附与pH值呈负相关,低pH环境中吸附量显著增加;吸附随溶液离子浓度的增加而略有增加。FT-IR的实验结果表明,腐植酸对磺酰脲除草剂的吸附存在明显的氢键作用,推测可能是磺酰脲脲桥上酰氨基的氢与腐植酸中羟基上的氧原子、均三氮苯环上的氮原子与腐植酸羟基上的氢原子之间形成了较强的氢键。

The adsorption behavior and mechanism of eight sulfonylurea herbicides on humic acid （HA） was studied with the method of batch equilibrium and the technique of Fourier transform infrared （FT-IR） was used to observe its sorption mechanism. The adsorption isotherms of eight sulfonylurea herbicides were obtained and the effect of pH and ionic strength on adsorption was assessed. It was shown that the sorption of sulfonylurea herbicides on HA followed the Freundlich equation, with the Freundlich constant Kf ranged from 354 to 3 413, which indicated that sulfonylurea herbicides were adsorbed strongly. Among the eight sulfonylurea herbicides, the chlorimuron-ethyl had the strongest sorption ability （Kf=3 413）, while the sulfometuron-methyl was the weakest （Kf=354）. The sorption amount of eight sulfonylurea herbicides in order was： chlorimuron-ethyl〉bensulfuron-methyl〉chlorsulfuron〉thifensulfuron-methyl〉metsulfuron-methyl〉pyrazosulfuron-ethyl〉nicosulfuron〉sulfometuron-methyl. The sorption of sulfonylurea herbicides on HA was negatively correlated with pH, but it was influenced positively by the ion concentration in solution, the adsorption increased with the increase of salt concentration, which was less distinct than pH, indicating pH was the more important factor influencing sorption. The hydrogen bonding was the mechanism acting in the sulfonylurea herbicides sorption.