Abstract Dyeing wastewater from textile industries is often contaminated with chemical pollutants, which causes severe water pollution problems that are challenging to treat. Recently, Zeolitic imidazolate frameworks (ZIFs) have attracted extensive research interest due to their potential applications in the removal of pollutants from wastewater. Herein, a Cd- zeolitic-imidazolate framework (Cd-ZIF-8) was synthesized and used as an adsorbent for the removal of methyl orange (MO) at different operating conditions. The prepared adsorbent was characterized using a variety of techniques, including X-ray diffraction (XRD), the Brunauer Emmett Teller (BET) method, FT-IR and scanning electron microscope (SEM). Its stability after adsorption was confirmed by XRD and pH tests. The effects of different variables, such as adsorbent dose, initial concentration, pH and temperature, were investigated to optimize the adsorption process. Adsorption parameters were determined by applying Langmuir and Freundlich models, and good fitting was observed for the Langmuir isotherm. Maximum MO adsorption capacities on Cd-ZIF-8 were 93.24 and 145.41 mg g-1 at 30° and 50°, respectively. Possible controlling mechanism and the potential rate-limiting steps were analyzed using Lagergren's pseudo-first-order and pseudo-second-order models, and the data were found to follow the pseudo-second-order equation. The prepared material was found to have good stability after the adsorption with no release of Cd ions over a wide range of pH. For a further explanation of the adsorption mechanism, interactions of MO molecules with the Cd and organic linkers of ZIF-8 were investigated using Density Functional Theory (DFT) cluster calculations.

中文翻译：

---

对镉沸石-咪唑酯骨架 Cd-ZIF-8 上甲基橙吸附行为的洞察：联合实验和理论研究

摘要 纺织工业印染废水经常受到化学污染物的污染，造成严重的水污染问题，难以处理。最近，沸石咪唑酯骨架（ZIFs）由于其在去除废水中的污染物方面的潜在应用而引起了广泛的研究兴趣。在此，合成了 Cd-沸石-咪唑酯骨架 (Cd-ZIF-8) 并将其用作吸附剂，用于在不同操作条件下去除甲基橙 (MO)。使用多种技术对制备的吸附剂进行表征，包括 X 射线衍射 (XRD)、Brunauer Emmett Teller (BET) 方法、FT-IR 和扫描电子显微镜 (SEM)。通过XRD和pH测试证实了其吸附后的稳定性。不同变量的影响，例如吸附剂剂量，研究了初始浓度、pH 值和温度以优化吸附过程。吸附参数通过应用 Langmuir 和 Freundlich 模型确定，并且观察到 Langmuir 等温线的良好拟合。在 30° 和 50° 时，Cd-ZIF-8 上的最大 MO 吸附容量分别为 93.24 和 145.41 mg g-1。使用 Lagergren 的伪一阶和伪二阶模型分析了可能的控制机制和潜在的限速步骤，发现数据遵循伪二阶方程。发现制备的材料在吸附后具有良好的稳定性，在较宽的 pH 范围内没有释放 Cd 离子。为了进一步解释吸附机制，