The synthesis of different metal oxide nanoparticles (NPs) (e.g., ZnO, MgO and SiO₂) using green methods is a promising alternative to traditional chemical methods. In this work, ZnO, MgO, and SiO₂ NPs were prepared using lemon peel extract. The synthesized NPs were characterized using Fourier transform infrared spectroscopy, UV–Visible spectroscopy, X-ray diffraction, and transmission electron microscopy. Also, the effects of the green synthesis of different NPs on the irrigation water quality, the availability of some heavy metals in soil and plants, and the productivity of Origanum majorana (marjoram) were studied in detail. The obtained results showed that the addition of the NPs resulted in noticeable variations in the removal percentages of Cu²⁺ and Fe³⁺ from aqueous solutions. The maximum values obtained for the adsorption of Cu(II) on ZnO, MgO, and SiO₂ NPs within the pH values of 3–5 were 89.9%, 83.3%, and 68.36%, respectively. Meanwhile, the maximum adsorption values of Fe(III) at pH 3.3 were 82%, 80%, and 65% for ZnO, MgO, and SiO₂ NPs, respectively. Clearly, the application of the NPs effectively reduced the available Cu²⁺ in the studied soil samples in the following order: Zn2 > Zn1 > Mg2 > Si2 > Mg1 > Si1 > C (control). The highest values of available Cu²⁺ were observed in the control treatment, whereas the lowest values were obtained when Zn2 was added. The same tendencies were observed with substantial concentrations of Fe. The addition of NPs to the soil samples positively affected the plants' Cu²⁺ uptake. The effects of NPs and the additions of Cu²⁺ and Fe³⁺ on the availability of nitrogen, phosphorus, and potassium (NPK) in the soil system were very completed and osculated from one treatment to another. The same tendencies were observed with the total concentration of NPK in plants.

In this study, cellulose fibers (Cf), extracted from sunflower seed husk, and different molar ratios of cerium titanate (Ce-Ti) NPs were prepared from sunflower seed husk extract by a green biosynthesis approach. Cf and Ce-Ti NPs were reacted via cross-linking reaction to synthesize a novel nanocomposite photocatalyst of Ce-Ti/Cf. Using Fourier-transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM-EDX) spectroscopy, all manufactured materials were characterized. The results obtained from FTIR and EDX analyses indicated that Cf and its nanocomposites (0.1 Ce-Ti/Cf, 0.3 Ce-Ti/Cf, and 0.5 Ce-Ti/Cf) were successfully prepared by harnessing biomass extract from sunflower seed husk. Furthermore, XRD revealed that the degree of crystallinity of the nanocomposites was enhanced by increasing the molar ratios of the Ce-Ti NPs. The photocatalytic activity of as-fabricated 0.1 Ce-Ti/Cf, 0.3 Ce-Ti/Cf, and 0.5 Ce-Ti/Cf nanocomposite samples was investigated on methylene blue (MB) and methyl orange (MO) dyes as model organic compounds found in wastewaters. The effects of dose, contact time, and pH on the photocatalytic activity of the synthesized nanocomposites, the photodegradation kinetic parameters of MB, and MO degradation with/without the addition of H₂O₂ were also studied. The results revealed that high photodegradation efficiency could be obtained as the ratio of TiO₂ in the Ce-Ti nanocomposite formula increases. Moreover, after sunlight irradiation, the adsorption capacity and the dye decomposition ratio significantly increase during the early contact time and reach equilibrium at about 240 and 120 min for 0.5 Ce-Ti/Cf nanocomposite photocatalyst in the absence and presence of hydrogen peroxide, respectively. In light of the obtained results and the practical wastewater treatment study conducted, the prepared photocatalyst from Ce-Ti/Cf nanocomposites could be a promising material for treating dye wastewater especially collected from Egypt.

The use of waste from various agricultural sectors has recently drawn increased interest from the scientific, technological, ecological, economic, and social fields. As such, in this study, a novel production of an affordable and environmentally friendly photocatalyst of silicotitanate (S1, S2, and S3) made from silica solution (extracted from rice husk ash) and various molar ratios of titanium (IV) 2-ethylhexyl-oxide is reported. Following that, chitosan/silicotitanate (CHMix) nanocomposite material was created through a crosslinking reaction between chitosan and fabricated silicotitanate (S2). Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX), as well as N₂ adsorption-desorption isotherm and zeta potential measurements were used to characterize each of the fabricated samples. Additionally, in comparison to neat chitosan, the newly fabricated material’s (CHMix) photocatalytic reactivity was investigated using two synthetic anionic dyes, reactive blue and Congo red, with decolorization rates of up to 95.76% and 99.9%, respectively. The decolorization results showed that CHMix is the most efficient photocatalyst for the degradation of reactive blue and Congo red. Reactive blue and Congo red’s molecular structures were almost completely broken when equilibrium was reached using sunlight, and the decolorization rate for both dyes was close to 100%. As a result, the combination of chitosan and silicotitanate, or CHMix, has an effective photocatalytic capability for dye degradation in both natural and concentrated sunlight.

Nanocrystalline magnesium silicate with high surface area has been synthesized by precipitation method using ammonium hydroxide and different surfactants. The results show that the anionic surfactant has a significant effect on the synthesis of nanocrystals. The method makes efficient use of stabilizing surfactant, and the nanocrystals show higher sorption efficiency and chemical stability. Transmission electron microscopy (TEM) shows a nanostructure consisting of different shapes according to different surfactants. According to the results of distribution coefficient on different silicate nanoparticles which applied in the polluted water in Egypt founded that, the selectivity order Fe³⁺ > Al³⁺ > Mn²⁺ >Zn²⁺> Pb²⁺.