Green synthesis of zinc oxide nanoparticles loaded on activated carbon prepared from walnut peel extract for the removal of Eosin Y and Erythrosine B dyes from aqueous solution: experimental approaches, kinetics models, and thermodynamic studies

Water contamination due to release of dye containing effluents is one of the environmental problems of serious concern today. The present study investigate the green synthesis of zinc oxide nanoparticles (ZnO-NPs) doped on activated carbon (AC) prepared from walnut peel extract and to estimate its efficiency in the removal of Eosin Y (Eo-Y) and Erythrosine B (Er-B) from its aqueous solution. The synthesized AC-ZnO was identified by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and the Brunauer-Emmett-Teller. The influence of various parameters such as pH, dosage of AC-ZnO, contact time, and concentrations of Eo-Y and Er-B was also studied. The pH 3 was observed as the optimum pH while the equilibrium was noticed to reach in 30 min at dosage of 1 g/L and initial concentration 100 mg/L for Eo-Y and Er-B adsorption onto AC-ZnO. The maximum adsorption capacity of Eo-Y and Er-B onto AC-ZnO was found to be 163.9 and 144.92 mg/g (and removal efficiencies of 95.11 and 98.31 %), respectively. The process of Eo-Y and Er-B adsorption on AC-ZnO was observed to be depended on the pseudo-second-order kinetic model which indicates chemisorption processes. Langmuir adsorption isotherm model test described the removal of Eo-Y and Er-B on AC-ZnO. The thermodynamic data indicated that the adsorption was endothermic process. Also, the values, S-BET and V-TOTAL, for the AC-ZnO were equal to 725.65 m(2)/g and 0.6004 cm(3)/g, respectively. The results of this study exhibited that AC-ZnO was a very effective method that can be used for the removal of Eo-Y and Er-B from aqueous solutions.

Automated summary

This study investigated the green synthesis of AC-ZnO prepared from walnut peel extract for the removal of Eo-Y and Er-B dyes in aqueous solutions. The maximum adsorption capacity of Eo-Y and Er-B onto AC-ZnO was found to be 163.9 and 144.92 mg/g, respectively. The adsorption process was dependent on the pseudo-second-order kinetic model and Langmuir adsorption isotherm model, and was determined to be an endothermic process.