Purpose

Pollution of surface water and groundwater by bulky molecules such as pesticides has been recognized as a major problem in many countries due to their persistence in aquatic environment and potential adverse health effects. The main purpose of this study is the development of a capable adsorbent to remove these bulky molecules from wastewater such as the pesticide Mesosulfuron-Methyl (MM) by reducing the diffusion path, to overcome the problems of diffusional limitations on microporous adsorbents.

Methods

The adsorption of mesosulfuron-methyl (MM) from aqueous solution is curried out using treated acid HY zeolite. Batch sorption equilibrium and kinetic experiments are conducted to evaluate the efficiency of these materials. Parent zeolites and their derivatives have been characterized by nitrogen adsorption–desorption, pyridine chemisorption followed by infrared spectroscopy and X-ray fluorescence.

Results

The acid treatment leads to an increase in the specific surface from 691 to 853 m² g^− 1 for HY(30) and from 631 to 806 m² g^− 1 for the HY(16.6) zeolites. It also leads to a reduction in Lewis acidity from 74 to 25 µmol g^− 1 and from 135 to 31 µmol g^− 1 for HY(30) and HY(16.6) zeolites respectively, and increases the adsorbent-adsorbate interaction. The adsorption capacity increased from 83 to 99 % after acid treatment. The equilibrium adsorption time is decreased from 15 h to 10 min for the HY(30)_A and from 20 h to 20 min for the HY(16.6)_A for an initial concentration of 20 mg L^− 1. The adsorption capacity depends on the pH solution, and the neutral form of the MM is more easily adsorbed into zeolite than the dissociated form via the framework bridged oxygen atoms. For all the samples, the pseudo-second-order kinetic model fits very well with the experimental data. In the case of the modified zeolites, the approaching equilibrium factor R_w decreases from 0.08183 to 0.00008 when the Lewis acid sites decrease; indicating that the equilibrium is reached more quickly. S-shape adsorption isotherms indicates that cooperative adsorption phenomena. Nevertheless, the shape of acid treated zeolites evolves to an L type indicating a significant enhancement of the adsorbent – adsorbate interactions inducing better adsorption efficiency.

Conclusions

Mesosulfuron-methyl adsorption has been successfully enhanced after acid treatments of zeolites HY.

中文翻译：

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酸处理的HY沸石对甲磺隆的吸附效果

 目的

由于农药等大分子在水生环境中的持久存在和潜在的不利健康影响，农药等大分子对地表水和地下水的污染已被许多国家视为一个主要问题。本研究的主要目的是开发一种能够通过减少扩散路径从废水中去除这些大分子的吸附剂，例如农药甲磺隆（MM），以克服微孔吸附剂的扩散限制问题。

 方法

使用处理过的酸性HY沸石从水溶液中吸附甲磺隆(MM)。进行批量吸附平衡和动力学实验来评估这些材料的效率。母体沸石及其衍生物通过氮吸附-解吸、吡啶化学吸附、红外光谱和 X 射线荧光进行了表征。

 结果

酸处理导致HY(30)沸石的比表面积从691增加到853 m ² g ^{- 1} ，HY(16.6)沸石的比表面积从631增加到806 m ² g ^{- 1} 。它还导致 HY(30) 和 HY(16.6) 沸石的路易斯酸度分别从 74 µmol g ^{- 1 降低至 25 µmol g - 1}和从 135 µmol g ^{- 1}降低至 31 µmol g - 1，并增加吸附剂-吸附质相互作用。酸处理后吸附容量从83%增加到99%。对于 20 mg L ^{- 1}的初始浓度，HY(30)_A 的平衡吸附时间从 15 小时减少到 10 分钟，HY(16.6)_A 的平衡吸附时间从 20 小时减少到 20 分钟。吸附能力取决于溶液的pH值，中性形式的MM比通过骨架桥接氧原子解离的形式更容易吸附到沸石中。对于所有样品，准二级动力学模型与实验数据非常吻合。对于改性沸石，当路易斯酸位减少时，接近平衡因子Rw从0.08183_减少到0.00008；表明达到平衡的速度更快。 S形吸附等温线表明协同吸附现象。然而，经过酸处理的沸石形状演变为 L 型，表明吸附剂 - 吸附质相互作用显着增强，从而导致更好的吸附效率。

 结论

对 HY 沸石进行酸处理后，成功增强了甲磺隆的吸附。