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.

Salinization of coastal aquifers is a serious issue affected by climate change and enhanced by overexploitation of groundwater resources. This research aims to explore the hydrogeochemical processes that cause salinization of groundwater in coastal aquifers, such as the area located between Barrani and Baqbaq, on the northwestern coast of Egypt. Various techniques were applied, including Gibbs plots and hydrochemical facies diagrams (HFE-D), ion ratios and stable isotope bivariate plots, statistical analyses, a groundwater quality index for seawater intrusion (GQI_SWI), and a seawater mixing index (SMI). Based on the total dissolved solids (TDS), groundwater can be classified into four groups: slightly saline (9%), moderately saline (45%), highly saline (43%), and salty water (3%). The geochemical properties were further catergorized on the basis of other parameters and ion ratios, such as Ca_excess, Na_deficit, Na/Cl, Cl/HCO₃, and Br/Cl, which suggest the influence of cation exchange, seawater, and marine sediment dissolution. Additionally, stable isotopes indicated two groups. One of these has relatively high salinity and low isotopic content and is affected by the leaching and dissolution of marine deposits. The other group is enriched in δ¹⁸O and δD content, with much higher salinity due to mixing with seawater and evaporation. The GQI_SWI categorizes groundwater as saline and mixed (55 and 41%, respectively), followed by saltwater (4%), whereas the SMI calculations indicate that about 10% of the groundwater samples are impacted by seawater. Finally, the areal distribution of GQI_SWI and SMI identified some patches along the coastline as well as other inland places located about 12.5 km away from the sea that have undergone saltwater intrusion. In conclusion, overexploitation of groundwater should be avoided because the amount of annual rainfall is very limited.