Abstract Adsorption of pesticides (heptachlor epoxide, dieldrin and endrin) onto modified bentonite by Keggin cation [Al30O8(OH)56(H2O)24]18+ denoted Al30 cation to form composite (Al30/B), has been investigated as a possible alternative method for their removal from aqueous solutions. The study was aimed to use a low-cost material as a step towards cleaner environment. Interestingly, these chemical modifications altered the physicochemical characteristics of bentonite in term of morphology, surface area and functionality which has been confirmed by using nitrogen adsorption–desorption isotherm, scanning electronic microscopy (SEM) and X-ray diffraction (XRD). Gas chromatography coupled to mass spectrometry (GC–MS) was used to identify and analyze the pesticides. Different physicochemical parameters were analyzed: contact time, adsorbent dose, pH, and temperature. The results showed that the removal percentage of pesticides on Al30/B was the highest at contact time of 5 h, adsorbent dosage of 25 mg, at pH 7.5, and at optimum temperature of 45 °C. Furthermore, the Kinetic study indicated that the adsorption of pesticides on Al30/B was well adapted to the pseudo-first order kinetic with a correlation coefficient near unity. The results of adsorption were fitted to the Langmuir and Freundlich isotherms. The Freundlich model represented the adsorption process better than Langmuir model, with correlation coefficients (R2) values range from 0.986 to 0.989. The Thermodynamic study suggested that the adsorption of pesticides was chemisorption, spontaneous and endothermic process. Therefore, Al30/B composite can be utilized effectively for removal of pesticides with efficiency up to 98%.

中文翻译：

---

有机氯农药在改性多孔 Al30/膨润土上的吸附：动力学和热力学研究

摘要 农药（七氯环氧化物、狄氏剂和异狄氏剂）被 Keggin 阳离子 [Al30O8(OH)56(H2O)24]18+ 表示的 Al30 阳离子吸附到改性膨润土上形成复合物 (Al30/B)，已被研究作为一种可能的替代方法从水溶液中去除的方法。该研究旨在使用低成本材料作为迈向更清洁环境的一步。有趣的是，这些化学改性改变了膨润土在形态、表面积和功能方面的物理化学特性，这已通过氮吸附-解吸等温线、扫描电子显微镜 (SEM) 和 X 射线衍射 (XRD) 得到证实。气相色谱与质谱联用 (GC-MS) 用于鉴定和分析农药。分析了不同的理化参数：接触时间、吸附剂剂量、pH、和温度。结果表明，在接触时间为 5 h、吸附剂用量为 25 mg、pH 为 7.5、最适温度为 45 °C 的条件下，Al30/B 对农药的去除率最高。此外，动力学研究表明，农药在 Al30/B 上的吸附很好地适应了准一级动力学，相关系数接近于 1。吸附结果符合 Langmuir 和 Freundlich 等温线。Freundlich 模型比 Langmuir 模型更能代表吸附过程，相关系数 (R2) 值范围为 0.986 至 0.989。热力学研究表明，农药的吸附是化学吸附、自发和吸热过程。因此，Al30/B复合材料可有效去除农药，效率高达98%。