Preparation, characterization and application of CuCrO2/ZnO photocatalysts for the reduction of Cr(VI)

The delafossite CuCrO₂ elaborated by sol-gel from 40 nm diameter colloid is optically active in the visible region. It is characterized physically and photoelectrochemically. The microstructure is fairly homogenous with a mean crystallite size of ca. 2 μm. The optical gap (1.30 eV), determined from the diffuse reflectance, is well suited to the sunlight spectrum. The Mott Schottky plot is characteristic of P-type conductivity with a flat band potential of -0.26 V_SCE. As application, the photoreduction of chromate is successfully achieved in air-equilibrated suspension CuCrO₂/ZnO (1/1). CuCrO₂ is photoactivated by visible light and the electrons in the conduction band (-1.34 V_SCE) are injected to ZnO. In the presence of salicylic acid, a conversion of Cr(VI) to Cr(III) of 57% is obtained under optimal conditions (pH 3 at 25℃, 5×10^-4 mol/L) because of the HCrO₄^- dark adsorption onto ZnO (4HCrO₄^- + 3C₇H₆O₃ + 18O₂ + 16H⁺ → 4Cr³⁺ + 21CO₂ + 19H₂O, ΔG⁰ = -557 kcal/mol). Prolonged illumination is accompanied by a deceleration in the photoactivity owing to the competitive water reduction, an issue of energetic concern. The hetero-system exhibits self sensitization for hydrogen production with an evolution rate of 149 μmol/(hr·g).     

Comparative study of heavy metal distribution in some coastal seaweeds of Alexandria, Egypt

The distribution of Cd, Cu, Fe, Hg, Mn, Ni, Pb, and Zn concentration in five algae species (Enteromorpha intestinalis, Enteromorpha linza, Ulva lactuca, Corallina mediterranea, Pterocladia capillacea) collected from three areas having different types of metal contamination along Alexandria coastal waters (Egypt) were determined by Atomic Absorption Spectrometry. The recovery study was carried out using a Certified Reference Material TORT-2. The obtained heavy metal contents indicate that different species demonstrate various degree of metal accumulation. Enteromorpha intestinalis (green algae) recorded the highest levels of Fe and Mn while Corallina mediterranea (Calcareous red algae) recorded the highest concentration of Pb, Ni, and Cd in the three areas under study. According to the present study, filamentous algae (Enteromorpha intestinalis) showed the ability to concentrate greater amount of trace elements than the foliaceous ones (Enteromorpha linza). In each area, mercury concentration has nearly the same value for all species under study.     

Effect of sewage on biodegradability of hydrocarbons in refinery wastewater

The effect of the microbial flora of municipal sewage, with special reference to faecal coliform and faecal streptococci groups, on the hydrocarbons biodegradation of the refinery wastewater from the Moustorod Oil Refinery has been studied. The results indicate that sewage with its microbial flora seems to have a significant role in the biodegradation of hydrocarbons in refinery wastewater. In addition, the early degradation in the wastewater seeded by sewage reveals that faecal streptococci, in addition to other microbial flora, have a significant role in the biodegradation of hydrocarbons.     

Speciation of organotin compounds in sediments of semi-closed areas along the Mediterranean coast of Alexandria

Organotin compounds were measured in sediments of four different semi-closed areas of the Mediterranean coast of Alexandria: the Eastern Harbour, Western Harbour, El-Max Bay, and Abu-Qir Bay. Due to the commercial trade activity inside the Western Harbour, in addition to the effect of wastes discharged from El Noubaria canal, it shows the highest concentrations of total tin (6.34 μg g^-1 dry weight), dibutyl tin (1.63 μg g^-1 wet weight), tributyl tin (0.33 μg g^-1 wet weight) and diphenyl tin (1.06 μg g^-1 wet weight) compared with other locations. The concentrations of TBT species showed the highest contents compared with DBT and DPhT compounds in all sampling areas. This trend might be due to the worldwide use of TBT not only as biocides in antifouling paints but also as preserving agents for wood, fungicides in agricultural activities, and heat and UV stabilizers of PVC, which results in a direct release of TBT into the water body, accumulation in aquatic fauna. There is also precipitation into sediments and a decrease in degradation rate into its derivatives. Variations, types, concentrations, and distribution of different organotin compounds are discussed in the areas under investigation. The study reveals a new record of organotin compounds along the Alexandria coast and makes comparisons with other surrounding areas of interest.     

Assessment of El-Salaam underground water for poultry use

Water quality for 13 wells in El-Salaam, in a new city near Cairo, has been investigated. Those wells were dug specifically to provide water for a company specializing in broiler poultry production. The water was analyzed for the following bacteriological parameters: total bacterial counts (10²–10⁴), total coliforms (<1?10²), fecal coliforms (<1?10²) fecal streptococci (<1?10³), aerobic spore formers (10²–10⁴) and total counts for Clostridia (<1?10³) per 100 mL. Chemical parameters such as pH, sulphate, alkalinity, hardness, and pesticides indicate that the water is unacceptable for poultry production. This study illustrates the need for monitoring and maintaining the integrity of groundwater sources at El-Salaam.     

Phytoremediation of aquaculture wastewater for water recycling and production of fish feed

Five plants were examined for their ability to remove nutrients from aquaculture wastewater and suitability as fish feed: alfalfa, white clover, oat, fall rye, barley. The seeds were first germinated in water in a hydroponic system, and the plants were fed wastewater from Tilapia production facility. Clover and alfalfa seeds were infected with fungus shortly after germination, and their roots were completely destroyed by day 14. Oat, rye and barley had the fastest growth and showed greater tolerance to fungal disease compared with alfalfa and clover. Although substantial amounts of soluble and insoluble substances were released by the seeds during the germination period, the plants were able to remove all the pollutants in wastewater and significant portions of those released substances. The total reductions in total solids, COD, NO3-N, NO2-N, phosphate and potassium ranged from 54.7% to 91.0%, 56.0% to 91.5%, 82.9% to 98.1%, 95.9% to 99.5%, 54.5% to 93.6% and 99.6% to 99.8%, respectively. Oat, barley and rye grow well in this type of hydroponic system and can be used as a fish feed after being supplemented with fat, Ca, Na, Mn and Fe. Oil seeds and the chlorides of these elements could be added to these plants when formulating the fish feed. For a continuous operation, a two-unit system could be configured to allow for one week germination and one week cleaning and startup in one unit while the other unit is in operation.     

Optimizing the specific surface area of fly ash-based sorbents for flue gas desulfurization

High performance sorbents for flue gas desulfurization can be synthesized by hydration of coal fly ash, calcium sulfate, and calcium oxide. In general, higher desulfurization activity correlates with higher sorbent surface area. Consequently, a major aim in sorbent synthesis is to maximize the sorbent surface area by optimizing the hydration conditions. This work presents an integrated modeling and optimization approach to sorbent synthesis based on statistical experimental design and two artificial intelligence techniques: neural network and genetic algorithm. In the first step of the approach, the main and interactive effects of three hydration variables on sorbent surface area were evaluated using a full factorial design. The hydration variables of interest to this study were hydration time, amount of coal fly ash, and amount of calcium sulfate and the levels investigated were 4-32 h, 5-15 g, and 0-12 g, respectively. In the second step, a neural network was used to model the relationship between the three hydration variables and the sorbent surface area. A genetic algorithm was used in the last step to optimize the input space of the resulting neural network model. According to this integrated modeling and optimization approach, an optimum sorbent surface area of 62.2m(2)g(-1) could be obtained by mixing 13.1g of coal fly ash and 5.5 g of calcium sulfate in a hydration process containing 100ml of water and 5 g of calcium oxide for a fixed hydration time of 10 h.     

Evaluation of thermodynamic parameters for adsorption of heavy metals by green adsorbents

Environmental Chemistry Letters - Thermodynamic parameters ΔG°, ΔH° and ΔS° are indicators of the possible nature of adsorption. This review&nbsp;summarizes the...     

Zingiber officinale ethanolic extract attenuates oxidative stress,steroidogenic gene expression alterations,and testicular histopathology induced by sodium arsenite in male rats

Environmental Science and Pollution Research - Arsenic (As) indelibly exists in the environment and may reach to a food chain. Flavors and herbs are recognized sources of natural antioxidants that...