Abstract
Organic dyes are discharged into aquatic systems from several industries causing severe environmental problems and toxicity to aquatic life. Therefore, it should be removed from water with a suitable process. Among several treatment processes, adsorption is one of the most attractive because of its simplicity, efficiency, and low operating cost. Moreover, adsorption supports environmental sustainability if a suitable adsorbent is used. In this work, a green route was followed to prepare ZnO: NiO nanocomposites using the Neem leaf extract as a stabilizing agent instead of harmful chemicals. Four different samples with three different ZnO:NiO ratios were prepared, namely: 3Z:1 N, 1Z:1 N, 1Z:3 N and 1Z:1 N without extract. The samples were characterized by XRD, TEM, SEM, IR, and UV, which all confirmed the successful synthesis of the nanocomposites. The nanocomposites were used for the adsorption of methyl orange (MO) from aqueous solutions. The four nanocomposites prepared with the aid of the extract showed a high sensitivity with 100% removal of MO from 6.25 ppm solutions. Furthermore, all the samples have a relatively fast kinetic with an equilibrium time less than 1 h. Also, the three samples maintained 100% removal efficiency after 5 adsorption-desorption cycles. The difference in particle size distribution obtained for the 1Z:1 N prepared with and without the extract confirms the important rule of the extract as a capping agent with an average size of 18 nm for the sample with the extract and 88 nm for the sample prepared without the extract. This difference in the particle sizes has been reflected on the adsorption performance of the two samples with a maximum adsorption capacity of 33 mg/g for the sample prepared with the extract compared to 6 mg/g for the sample without the extract.