This study aims to optimize the adsorption process of gallic acid (GA) on Cu-Al layered double hydroxides (LDHs) synthesized via a co-precipitation method at various pH levels. The procedure is based on the adsorption of organic pollutants from aqueous solutions, with evaluations carried out based on operational parameters such as pH, initial concentration, and adsorbent quantity. Two series of LDHs were compared: one using aluminum extracted from saline slags and the other using a commercial aluminum salt as source of aluminum. Saline slags, a by-product of aluminum recycling, are particularly hazardous due to their high toxicity and potential for environmental contamination. Extracting aluminum from these slags and using it in the synthesis of LDHs not only helps in eliminating a dangerous waste but also creates materials with beneficial environmental applications. The adsorption process was optimized using response surface methodology (RSM) coupled with Box-Behnken design (BBD) to assess the effects of key operational parameters. Besides gallic acid, other organic pollutants such as diclofenac and salicylic acid were also evaluated for removal from aqueous solution. The LDH /LDO were characterized by X-ray diffraction (XRD), ATR infrared spectroscopy (ATR-IR), scanning and transmission electron microscopy (SEM/TEM), thermogravimetric analysis (TGA), and nitrogen adsorption at −196 °C. The merit data indicate that the material synthesized at pH = 9 with extracted aluminum exhibits superior adsorption capacity for gallic acid, demonstrating the highest removal rate, nearly reaching 100 %, and achieving equilibrium more quickly than other samples. This superior adsorption performance is also notable for salicylic acid and diclofenac. After four regeneration cycles, the adsorption rate of the adsorbent remains stable, indicating that CCA9 maintains a consistent and efficient adsorption performance. This highlights the robustness of the material and its high reusability in prolonged adsorption applications. Molecular dynamics simulations (MDS) revealed that the adsorption process occurs spontaneously, driven by weak interactions: van der Waals, intermolecular, hydrogen bonding, π-interactions and short contacts.

中文翻译：

---

增强盐水铝渣中 Cu-Al 层状双氢氧化物的吸附性能：从响应面方法和分子动力学模拟中获得见解


本研究旨在优化没食子酸 （GA） 在不同 pH 值下通过共沉淀法合成的 Cu-Al 层状双氢氧化物 （LDH） 上的吸附过程。该程序基于从水溶液中吸附有机污染物，并根据 pH 值、初始浓度和吸附剂数量等操作参数进行评估。比较了两个系列的 LDHs：一个使用从盐渍渣中提取的铝，另一个使用商业铝盐作为铝源。盐矿渣是铝回收的副产品，由于其高毒性和潜在的环境污染而特别危险。从这些炉渣中提取铝并将其用于合成 LDH 不仅有助于消除危险废物，还可以创造出具有有益环境应用的材料。使用响应面法 （RSM） 结合 Box-Behnken 设计 （BBD） 优化吸附过程，以评估关键操作参数的影响。除了没食子酸外，还评估了其他有机污染物，如双氯芬酸和水杨酸，以从水溶液中去除。在 −196 °C 下，通过 X 射线衍射 （XRD）、ATR 红外光谱 （ATR-IR）、扫描和透射电子显微镜 （SEM/TEM）、热重分析 （TGA） 和氮气吸附对 LDH /LDO 进行了表征。 品质数据表明，在 pH = 9 时用提取铝合成的材料表现出优异的没食子酸吸附能力，表现出最高的去除率，几乎达到 100%，并且比其他样品更快地达到平衡。这种卓越的吸附性能对于水杨酸和双氯芬酸也值得注意。 经过 4 次再生循环后，吸附剂的吸附速率保持稳定，表明 CCA9 保持了一致且高效的吸附性能。这突出了材料的坚固性及其在长时间吸附应用中的高可重用性。分子动力学模拟 （MDS） 表明，吸附过程是自发发生的，由弱相互作用驱动：范德华、分子间、氢键、π相互作用和短接触。