Green mediated combustion synthesis of copper zinc oxide using Eryngium planum leaf extract as a natural green fuel: Excellent adsorption capacity towards Congo red dye

In the present study, meso/microporous CuO/ZnO nanostructures were synthesized via a green mediated solution combustion method by Eryngium planum leaf extract as natural fuel for the first time. Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectrometer (FTIR), Thermogravimetric/differential thermal analysis (TGA/DTA), and N-2 adsorption-desorption analyses were applied to characterize the as-prepared samples. The total pore volume and average pore diameter of the CuO/ZnO nanostructures were 0.06945 cm(3)/g and 4.76 nm, respectively. A batch adsorption test was conducted using the as-synthesized samples to evaluate their ability to remove congo red (CR) dye. In the following, the effective parameters in the adsorption of CR by CuO/ZnO nanostructures, including contact time, adsorbent dosage, pH of the solution, initial dye solution concentration, and temperature, were investigated in detail. Also, the kinetic, isotherm, and thermodynamic studies were evaluated. The results indicated that the intra-particle diffusion model (R-2 = 0.9990) and pseudo-second-order model (R-2 = 0.9998) are suitable models for describing the adsorption rate at the early (0-60 min) and later (60-240 min) times, respectively. According to the Langmuir isotherm model, the maximum adsorption capacity of CR by CuO/ZnO was found to be 357.14 mg/g. Moreover, the negative value for each of the parameters of Delta H degrees and Delta S degrees indicates that the adsorption at the solid/solution interface is exothermic and non-random during the process, respectively. Therefore, the proposed eco-friendly and inexpensive green synthesis method can be considered to develop new interesting materials to remove contamination from industrial wastewaters.

Automated summary

In this study, CuO/ZnO nanostructures with meso/microporous structures were synthesized using a green mediated solution combustion method. The synthesized samples were characterized using various techniques and their adsorption capacity for CR dye was evaluated. The effects of various parameters on the adsorption process were investigated, and kinetic, isotherm, and thermodynamic studies were conducted. The results showed that the synthesized CuO/ZnO nanostructures are effective in removing CR dye from industrial wastewaters.