No abstract

The enhancing breakdown of dyes using facile, novel and eco-friendly photocatalyst without remaining any hazards secondary intermediates from the dye species regarded one of the most challenges to the healthy world. A novel facile method was used to synthesize reduced graphene oxide (rGO) with various doping ratios of silver nanoparticles (Ag NPs) and applied as photocatalyst to enhancing removal of Congo red (CR) dye using UV light irradiation from aqueous solution. Some characterization features such as UV-diffuse reflectance spectra, TEM, SEM, FTIR, X-ray diffraction, and EDX were measured to demonstrate the energy gap, morphology, size distribution, crystalline nature, phase structure, and elemental compositions of as-synthesized nanoparticles. The effect of some important factors such as pH of solution, initial CR concertation (Co), amount of rGO@Ag (g) and contact time (t) were studied to detect the optimum adsorption condition. The results indicated that, the maximum CR dye photodegradation is obtained at pH 7, 120 min, 50 mg/L initial CR concentration and 0.4 g/L photocatalyst dosage. The photodegradation data declared that, the higher the Ag doping ratio, the higher the degrading efficiency. Isotherm and kinetic studies showed that Langmuir and Freundlich models and the pseudo-second-order model are well fitting the adsorption process with maximum CR adsorption values ranging between 86.95 and 98.04 mg/L with corresponding R2 > 0.99.

Sediments act as a sink or source of pollution under various conditions. Moreover, they can serve as pollution indicators. The present research aims to evaluate sediment quality associated with its content in heavy metals and the potential ecological risk, focusing on the sub-branches of Nile River (Rayahs) in Egypt, including El-Tawfiky (RT), El-Menoufy (RM), El-Behary (RB), and El-Nassery (RN). According to the results, El-Rayahs sediments are characterized by an increasing sand fraction, followed by mud. Regarding metals pollution, Cd registered the highest pollution ranking, whereas Fe, Mn, Zn, Pb, and Ni exhibited the lowest effect. Furthermore, the ecological risk for El-Rayahs sediments increases northward; however, most sites either showed slight pollution or did not record any degree of contamination, except the northern stretch of El-Behery (El-Mahmoudia Canal), which is a very high-polluted zone, with high ecological risk according to the contamination degree (Cd) and potential ecological risk (RI) indices.