Zn-Fe layered double hydroxides was prepared by three methods of coprecipitation: coprecipitation at constant pH (pH Cst), coprecipitation at variable pH (pH Var), and direct coprecipitation (DC). The Zn-Fe LDH was utilized as an effective adsorbent for removal of cochineal red dye (CR) from aqueous solutions. The structure of the prepared materials was characterized by XRD and FTIR. The effects of various experimental parameters such as initial pH, adsorbent dosage, initial dye concentration, contact time, and temperature have been investigated using a batch adsorption technique and their optimum conditions were ascertained to find the optimal conditions for a maximum adsorption. At 50 mg/l cochineal red dye concentration and 50 mg of adsorbent mass, Zn-Fe LDH prepared by coprecipitation at constant pH had 1.09 and 1.31 times more adsorption capacity than Zn-Fe LDH prepared by direct coprecipitation and coprecipitation at variable pH, respectively. The adsorption capacity of the studied adsorbents was in the order pH Cst > DC > pH Var. The removal of Cochineal Red dye reaches its maximum of 96.74 %, 95.70 %, and 92.48 % after 40 min, 50 min, and 80 min for Zn-Fe LDH prepared by coprecipitation at constant pH, direct coprecipitation, and coprecipitation at variable pH respectively with the use of the optimum masses of 50 mg, 80 mg, and 100 mg for these respective materials. Freundlich and Temkin isotherm models were applied to describe the equilibrium adsorption experimental data. The cochineal red dye adsorption follows the Temkin model for the materials synthesized by coprecipitation at variable pH and direct coprecipitation. This indicates that the adsorption is characterized by a uniform distribution of binding energies between the molecules adsorbed and adsorbents. The Zn-Fe LDH prepared by coprecipitation at constant pH follows the Freundlich model, indicating the heterogeneous nature of adsorption sites. The adsorption kinetics of the dye obeyed pseudo-second-order kinetic model. Thermodynamic study indicates that the adsorption process is spontaneous and endothermic in nature.

Zn-Fe 层状双氢氧化物通过三种共沉淀方法制备：恒定 pH 共沉淀 (pH Cst)、可变 pH 共沉淀 (pH Var) 和直接共沉淀 (DC)。Zn-Fe LDH 被用作从水溶液中去除胭脂虫红染料 (CR) 的有效吸附剂。制备的材料的结构通过XRD和FTIR表征。使用分批吸附技术研究了各种实验参数（如初始 pH 值、吸附剂剂量、初始染料浓度、接触时间和温度）的影响，并确定了它们的最佳条件以找到最大吸附的最佳条件。50 毫克/升在胭脂虫红染料浓度和 50 mg 吸附剂质量下，通过在恒定 pH 下共沉淀制备的 Zn-Fe LDH 的吸附容量分别是通过直接共沉淀和在可变 pH 下共沉淀制备的 Zn-Fe LDH 的 1.09 和 1.31 倍。所研究的吸附剂的吸附能力的顺序为 pH Cst > DC > pH Var。对于通过恒定 pH 共沉淀、直接共沉淀和可变 pH 共沉淀制备的 Zn-Fe LDH，在 40 分钟、50 分钟和 80 分钟后，胭脂虫红染料的去除率分别达到 96.74 %、95.70 % 和 92.48 %对这些各自的材料使用 50 mg、80 mg 和 100 mg 的最佳质量。Freundlich 和 Temkin 等温线模型用于描述平衡吸附实验数据。胭脂虫红染料吸附遵循 Temkin 模型，适用于通过可变 pH 共沉淀和直接共沉淀合成的材料。这表明吸附的特点是被吸附分子和吸附剂之间的结合能分布均匀。在恒定 pH 下通过共沉淀制备的 Zn-Fe LDH 遵循 Freundlich 模型，表明吸附位点的异质性。染料的吸附动力学服从准二级动力学模型。热力学研究表明吸附过程是自发吸热的。这表明吸附的特点是被吸附分子和吸附剂之间的结合能分布均匀。在恒定 pH 下通过共沉淀制备的 Zn-Fe LDH 遵循 Freundlich 模型，表明吸附位点的异质性。染料的吸附动力学服从准二级动力学模型。热力学研究表明吸附过程是自发吸热的。这表明吸附的特点是被吸附分子和吸附剂之间的结合能分布均匀。在恒定 pH 下通过共沉淀制备的 Zn-Fe LDH 遵循 Freundlich 模型，表明吸附位点的异质性。染料的吸附动力学服从准二级动力学模型。热力学研究表明吸附过程是自发吸热的。