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Textile dyes widely used in industrial products are known as a major threat to human health and water ecological security. On the other hand, sol gel represents a principal driver of the adoption of dispersive solid-phase microextractors (d-µ SPME) for pollutants residues in water. Thus, the current study reports a new and highly rapid and highly efficient hybrid sol-gel-based sponge polyurethane foam as a dispersive solid-phase microextractor (d-µ-SPME) platform packed mini-column for complete preconcentration and subsequent spectrophotometric detection of eosin Y textile dye in wastewater. The unique porous structure of the prepared sol-gel immobilized polyurethane foams (sol-gel/PUF) has suggested its use for the complete removal of eosin Y dye (EY) from water. In the mini-column, the number (N) of plates, the height equivalent to the theoretical plates (HETP), the critical capacity (CC), and the breakthrough capacities (BC) of the hybrid sol-gel-treated polyurethane foams towards EY dye were determined via the breakthrough capacity curve at various flow rates. Under the optimum condition using the matrix match strategy, the linear range of 0.01–5 µg L−1, LODs and LOQs in the range of 0.006 µg L−1, and 0.01 µg L−1 for wastewater were achieved. The intra-day and inter-day precisions were evaluated at two different concentration levels (0.05 and 5 μg L−1 of dye) on the same day and five distinct days, respectively. The analytical utility of the absorbents packed in pulses and mini-columns to extract and recover EY dye was attained by 98.94%. The column could efficiently remove different dyes from real industrial effluents, and hence the sol-gel/PUF is a good competitor for commercial applications. The findings of this research work have strong potential in the future to be used in selecting the most suitable lightweight growing medium for a green roof based on stakeholder requirements. Therefore, this study has provided a convenient pathway for the preparation of compressible and reusable sponge materials from renewable biomass for efficient removal of EY from the water environment.

Halloysite (HS) nanoclay was used for the environmental treatment of desalination brine water discharge via the adsorptive removal of selected heavy metals ions; zinc, iron, nickel, and copper, as well as salinity. Different techniques were used for the characterization of the HS nanoclay and it was found that HS nanoclay exists as transparent hollow nanotubes with high surface area. The study showed that most of the heavy metal ions could be removed successfully using the HS nanoclay in a few minutes, at normal conditions. The adsorptive removal of zinc, iron, nickel, and copper, as well as salinity on HS nanoclay was explored kinetically. It was concluded that the pseudo-second-order kinetic model was able to describe the remediation process. In addition, it was found that most of the heavy metals and salinity were removed from the desalination plant outfall brine discharge and the final concentrations were lower than those in the control and standard samples.

Elemental ratios (δ 13 C, δ 15 N and C/N) and carbon and nitrogen concentrations in macrophytes, sediments and sponges of the hypersaline Al-Kharrar Lagoon (KL), central eastern Red Sea coast, were measured to distinguish their sources, pathways and see how they have been influenced by biogeochemical processes and terrestrial inputs. The mangroves and halophytes showed the most depleted δ 13 C values of –27.07±0.2 ‰ and –28.34±0.4 ‰, respectively, indicating their preferential 12 C uptake, similar to C3-photosynthetic plants, except for the halophytes Atriplex sp. and Suaeda vermiculata which showed δ 13 C of –14.31±0.6 ‰, similar to C4-plants. Macroalgae were divided into A and B groups based on their δ 13 C values. The δ 13 C of macroalgae A averaged –15.41±0.4 ‰, whereas macroalgae B and seagrasses showed values of –7.41±0.8 ‰ and –7.98 ‰, suggesting uptake of HCO 3 – as a source for CO 2 during photosynthesis. The δ 13 C of sponges was –10.7±0.3 ‰, suggesting that macroalgae and seagrasses are their main favoured diets. Substrates of all these taxa showed δ 13 C of –15.52±0.8 ‰, suggesting the KL is at present a macroalgae-dominated lagoon. The δ 15 N in taxa/sediments averaged 1.68 ‰, suggesting that atmospheric N 2 -fixation is the main source of nitrogen in/around the lagoon. The heaviest δ 15 N (10.58 ‰) in halophytes growing in algal mats and sabkha is possibly due to denitrification and ammonia evaporation. The macrophytes in the KL showed high C %, N %, and C/N ratios, but this is not indicated in their substrates due possibly to a rapid turnover of dense, hypersaline waters carrying most of the detached organic materials out into the Red Sea. The δ 13 C allowed separation of subaerial from aquatic macrophytes, a proxy that could be used when interpreting paleo-sea level or paleoclimatic changes from the coastal marine sediments.

The aim of this study was to determine the compositions of carbohydrates, phenolic compounds, fatty acids (FAs), and amino acids (AAs) of four Rea Sea halophytes: Anabasis ehrenbergii, Suaeda aegyptiaca, Suaeda monoica, and Zygophyllum album. The results showed that S. aegyptiaca and S. monoica were rich in gallic acid with 41.72 and 47.48 mg/g, respectively, while A. ehrenbergii was rich in naringenin with 11.88 mg/g. The polysaccharides of the four species were mainly composed of galactose (54.74%) in A. ehrenbergii, mannose (44.15%) in S. aegyptiaca, glucose and ribose (33 and 26%, respectively) in S. monoica, and arabinose and glucose (36.67 and 31.52%, respectively) in Z. album. Glutamic acid and aspartic acid were the major AAs in all halophyte species with 50–63% and 10–22% of the total AAs, respectively. The proportion of unsaturated fatty acids (UFA) of the four species was 42.18–55.33%, comprised mainly of linolenic acid (15.54–28.63%) and oleic acid (5.68–22.05%), while palmitic acid (23.94–49.49%) was the most abundant saturated fatty acid (SFA). Phytol and 9,19-cyclolanost-24-en-3β–ol represented the major unsaponifiable matter (USM) constituents of S. monoica and A. ehrenbergii with proportions 42.44 and 44.11%, respectively. The phenolic fraction of S. aegyptiaca and S. monoica demonstrated noteworthy antioxidant activity with IC50 values of 9.0 and 8.0 μg/mL, respectively, while the FAs fraction of Z. album exhibited potent cytotoxic activity against Huh-7, A-549, and Caco-2 cancer cell lines with IC50 values of 7.4, 10.8, and 11.8 μg/mL, respectively. Our results indicate that these plants may be considered a source of naturally occurring compounds with antioxidant and anticancer effects that could be suitable for future applications.

The importance of selenium in the marine environment is highlighted by its bilateral behavior as a nutrient and toxic element. The cathodic stripping voltammetry validated method was used to determine the selenium concentration. The concentration of total dissolved selenium (TDSe) in Al-Arbaeen and Sharm Obhur lagoons along the eastern Red Sea coastal waters was determined. The total selenium concentration in seven fish species’ muscles was determined. TDSe in the surface water of Al-Arbaeen and Sharm Obhur lagoons showed a maximum concentration of 18.56 and 8.38 nM, respectively. TDSe in the surface water of Al-Arbaeen revealed high concentrations near the wastewater discharging pipes in the lagoon. The linear regression between the TDSe and salinity reflected that the discharged water is the source of selenium with a significant negative correlation of (R2 = 0.80, p < 0.05). In contrast, TDSe in the surface water of Sharm Obhur showed a significant positive correlation (R2 = 0.78, p < 0.05). In the lagoon head, hypoxic and anoxic conditions were dominant. This condition reflected the low TDSe concentration and may affect the selenium chemical forms’ abundance in the lagoon. Two fish species Herklotsichthys punctatus and Herklotsichthys revealed high concentrations of 3.99 and 2.40 µg/g, respectively, which exceeded the permissible levels of the WHO, FAO, and ASTDR.

For any coastal desalination plant, the most effective and practical way to dispose of their brine is to thermally discharge it into the sea via outfalls at some distance from the coast. This study focused on the environmental impacts associated with brine and thermal discharge arising from seawater desalination plants at Yanbu, Saudi Arabia, on the southeastern coast of the Red Sea. The impacts associated with recirculation patterns and dispersions were investigated with the calibrated three-dimensional numerical model Delft3d. The environmental impact assessment and the process of identification and characterisation could help improve strategies for better planning and management of the technological solutions related to desalination. Analysis of the model simulations for the different seasons also suggested that around the outfall location, the magnitude of the flow was always high when considered together with the presence of seasonal eddy circulations. Although the tidal flow is lower, the ambient current and wind cause the far-field discharge to spread along the north–south direction during the winter and summer. The thermal and brine dispersion and environmental compliance were assessed in terms of the extent of dispersion. The well-mixed environment caused more rapid dispersion. From the impact level assessment perspective, the study indicated rapid dilution and dispersion of the wastewater at the study region. The present offshore outfall and further offshore locations were far enough to ensure quick dispersion.

As mercury (Hg) biosensors are sensitive to only intracellular Hg, they are useful in the investigation of Hg uptake mechanisms and the effects of speciation on Hg bioavailability to microbes. In this study, bacterial biosensors were used to evaluate the roles that several transporters such as the glutathione, cystine/cysteine, and Mer transporters play in the uptake of Hg from Hg-thiol complexes by comparing uptake rates in strains with functioning transport systems to strains where these transporters had been knocked out by deletion of key genes. The Hg uptake into the biosensors was quantified based on the intracellular conversion of inorganic mercury (Hg(II)) to elemental mercury (Hg(0)) by the enzyme MerA. It was found that uptake of Hg from Hg-cysteine (Hg(CYS)2) and Hg-glutathione (Hg(GSH)2) complexes occurred at the same rate as that of inorganic complexes of Hg(II) into Escherichia coli strains with and without intact Mer transport systems. However, higher rates of Hg uptake were observed in the strain with a functioning Mer transport system. These results demonstrate that thiol-bound Hg is bioavailable to E. coli and that this bioavailability is higher in Hg-resistant bacteria with a complete Mer system than in non-resistant strains. No difference in the uptake rate of Hg from Hg(GSH)2 was observed in E. coli strains with or without functioning glutathione transport systems. There was also no difference in uptake rates between a wildtype Bacillus subtilis strain with a functioning cystine/cysteine transport system, and a mutant strain where this transport system had been knocked out. These results cast doubt on the viability of the hypothesis that the entire Hg-thiol complex is taken up into the cell by a thiol transporter. It is more likely that the Hg in the Hg-thiol complex is transferred to a transport protein on the cell membrane and is subsequently internalized.

Photocatalytic degradation of polychlorinated biphenyls (PCBs) in seawater was successfully achieved at laboratory level with UV light and at pilot-plant scale under natural solar radiation using carbon-modified titanium oxide (CM-n-TiO2) nanoparticles. The photocatalytic performance of CM-n-TiO2 was comparatively evaluated with reference n-TiO2 under identical conditions. As a result of carbon incorporation, significant enhancement of photodegradation efficiency using CM-n-TiO2 was clearly observed. To optimize the operating parameters, the effects of catalyst loading and pH of the solution on the photodegradation rate of PCBs were investigated. The best degradation rate was obtained at pH 5 and CM-n-TiO2 loading of 0.5 g L−1. The photodegradation results fitted the Langmuir-Hinshelwood model and obeyed pseudo-first-order reaction kinetics.

The bioactive constituents of sea cucumber Holothuria atra were investigated, and four sulfated holostan-type triterpene glycosides ( 1 – 4 ) along with other seven know metabolites were obtained. On the basis of the extensive NMR and ESI-MS data, the structures of triterpenoid saponins were assigned as a new compound echinoside B 12- O -methyl ether ( 1 ), and known echinoside B ( 2 ), 24-dehydroechinoside B ( 3 ), and holothurin B ( 4 ). The extract and isolated saponins displayed weak antioxidant DPPH radical scavenging activities, where echinoside B ( 2 ) showed the highest value at 26.41%. However, 24-dehydroechinoside B ( 3 ) showed mild antioxidant-reducing power activity (0.19 nm), compared to the synthetic antioxidant (BHT). Both compounds 2 and 3 exhibited moderate cytotoxic activity by reducing the viability of Ehrlich ascites carcinoma cells to 41.0% and 42.2%, respectively, compared to the drug control vincristine (95.2%).

Photocatalytic reduction of CO2 in seawater into chemical fuel, methanol (CH3OH), was achieved over Cu/C-co-doped TiO2 nanoparticles under UV and natural sunlight. Photocatalysts with different Cu loadings (0, 0.5, 1, 3, 5, and 7 wt%) were synthesized by the sol–gel method and were characterized by XRD, SEM, UV–Vis, FTIR, and XPS. Co-doping with C and Cu into TiO2 remarkably promoted the photocatalytic production of CH3OH. This improvement was attributed to lowering of bandgap energy, specific catalytic effect of Cu for CH3OH formation, and the minimization of photo-generated carrier recombination. Co-doped TiO2 with 3.0 wt% Cu was found to be the most active catalyst, giving a maximum methanol yield rate of 577 μmol g-cat−1 h−1 under illumination of UV light, which is 5.3-fold higher than the production rate over C-TiO2 and 7.4 times the amount produced using Degussa P25 TiO2. Under natural sunlight, the maximum rate of the photocatalytic production of CH3OH using 3.0 wt% Cu/C-TiO2 was found to be 188 μmol g-cat−1 h−1, which is 2.24 times higher than that of C-TiO2, whereas, no CH3OH was observed for P25.