A novel composite silver nanoparticles loaded calcium oxide stemming from egg shell recycling: A potent photocatalytic and antibacterial activities

Industrial wastewater resulted from textile dyeing process is considered as a big environmental problem. Therefore, recycling of wastewater offers environmental and economic values specially if the materials used are resulted from recycling of other kinds of waste. From this point of view and for the first time this work deals with the study the wastewater recycling by calcium oxide resulted from eggshell recycling. Calcium oxide (CaO) nanocrystals were created by the thermal annealing of chicken egg shell at 1100  C for 2 h s. Heat treatment at 200  C in air for 2 h s of the resulted CaO with silver oxalate gave the novel composite, silver nanoparticles loaded calcium oxide (Ag-NPs @ CaO). By applying electronic spectra (UV eVis), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron mi- croscopy with the energy dispersion spectrum analysis (SEM-EDX) and transmittance electronic mi- croscope (TEM), the materials were characterized. The energy band gap was calculated from the equation of Tauc for CaO and Ag-NPs@CaO and measured to be 2.1 and 2 eV, respectively. Indigo carmine (IC) as a model of photocatalytic decolorization was performed using both CaO and Ag@CaO nanoparticles under sunlight exposure. The impacts of various variables such as solution pH, dose quantity, temperature and irradiation time were studied. Both catalysts displayed an effective photocatalytic activity in IC decol- orization but Ag@CaO composite displayed a stronger activity than CaO. The percentages of dye degradation were z99.21% and 99.45% in case of CaO and Ag@CaO, respectively. The antibacterial effi- ciency was measured against some Gram-negative and Gram-positive bacteria. Ag@CaO provided powerful weapons against the drug-resistant bacteria. These findings give a promising and economic strategy for all those who are interested in industries which involve dyeing process.