Removal of Amido black 10B through adsorption–photocatalytic degradation synergestic effect of doped Cr- ZnO/CDs nanocomposites under solar light

In this work, chromium doped ZnO/carbon dots (Cr-ZnO/CDs) nanocomposite was used for removal of Amido black 10B (AB) through adsorption–photocatalytic synergestic effect. In order to synthesis of the novel nanocomposite, in the first step, a green strategy have been successfully applied for the synthesis of carbon dots (CDs) from pine leaf, based on hydrothermal treatment [1]. The as-synthesized CDs exhibited many advantages including high fluorescence intensity, water solubility, non-toxic and eco-friendly. In the next step, Cr-ZnO/CDs nanocomposite was synthesized using the facile one-step hydrothermal method. One of the great advantages of this method is that the synthesis was carried out at lower temperature (at 100ºC) than other methods [2]. The CDs and Cr-ZnO/CDs nanocomposite were characterized using X-ray diffraction (XRD), Raman spectrometer (Raman), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and UV-vis spectrophotometry. The photocatalytic degradation and adsorption effects of Cr-ZnO and Cr-ZnO/CDs nanocomposits on AB (as a sample), which is an amino acid staining azo dye, were investigated. The results indicated that the CDs had a significant influence in improving the effectiveness of Cr-ZnO nanocomposite. Removing of AB, as a pollutant from water, was performed by dual-functionality properties of Cr-ZnO/CDs nanocomposits. This nanocomposite can adsorb a high percentage of the dye and then degrade the remaining dye by its own photocatalytic property. In this way, this nanocomposite can remove nearly 100% of the dye. The effect of experimental variables such as pH, amount of the nanocomposite and dye concentration on the dye removal were investigated. The results showed that Cr-ZnO/CDs nanocomposite, under optimum conditions, even is capable to removal of the dye concentrations higher than 100 ppm. Also, this nanocomposite can be eliminated other azo dyes such as methyl orange (MO) and congo red (CR). Under the optimal conditions, about 98% of AB was removed rapidly (less than 10 min) by the Cr-ZnO/CDs nanocomposite from wastewater in room temperature [3]. This composite can recovery in alkaline media for reusing.