چكيده به لاتين
The objective of this research is the synthesis of morphological zinc oxide nanostructures using plant mucilages from four substances: Cydonia oblonga (quince seed), Lepidium sativum (garden cress), Plantago major (plantain), and Plantago ovata (psyllium) as directing agents, and to investigate the factors influencing morphology for the purpose of dye removal from water. Initially, the effect of influencing factors in the synthesis stage was studied using the hydrothermal method through Taguchi design of experiments L16. The optimal conditions were investigated to achieve the minimum average crystallite size. The results of this stage indicated that the optimal sample was obtained with a zinc nitrate hexahydrate concentration of 0.1 M, a reaction time of 3 hours, Plantain mucilage, a mucilage dosage of 15 ml, and a urea-to-zinc molar ratio of 1, yielding an average crystallite size of 20.9 nm. Subsequently, to achieve the optimal result of the minimum crystallite size, a "one-factor-at-a-time" experimental design based on the screened data from Taguchi L16 was employed. The results showed that the optimal sample was obtained with a zinc nitrate hexahydrate concentration of 0.05 M, a reaction time of 3 hours, Plantain mucilage, a mucilage dosage of 15 ml, and a urea-to-zinc molar ratio of 0.5, yielding an average crystallite size of 14.5 nm. The various characteristics of the particles were examined using FESEM, XRD, and EDX analyses, which demonstrated that the morphology of the optimized sample was rod-like, with a length of approximately 8 nm. Subsequently, a batch system was employed in this study to remove Congo red dye using the morphological zinc oxide. Sample 11, with a maximum adsorption capacity of 9.986 mg/g, was selected as the optimal adsorbent. The characteristics of the optimal adsorbent were analyzed using EDX, BET, FESEM, and FTIR tests, revealing that the optimal adsorbent exhibited a rod-like morphology with an average length of 16 nm and a specific surface area of 10.361 m2/g. The effects of adsorption parameters, including contact time, solution pH, adsorbent dosage, initial dye concentration, temperature, adsorbent regeneration, and stirring speed, were also investigated. The experimental data were fitted to three isotherm models (Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin), and the results indicated that the Langmuir isotherm provided the best fit for the experimental data regarding Congo red dye removal. The maximum adsorption capacity obtained from the Langmuir isotherm was 120.481 mg/g at room temperature. Additionally, the pseudo-second-order kinetic model provided a better description of the experimental data. Finally, the thermodynamic results indicated that the process was spontaneous and exothermic, with negative entropy, suggesting a more ordered system.
