27 research outputs found
Sorption and Desorption Processes of Organic Contaminants on Carbonaceous Materials
No full textSorption is considered the most important abiotic process for determining the fate and transport of organic contaminants in the environment. Hence, we investigated whether sorption is fully reversible or whether a irreversibly sorbed pollutant fraction remains in the sorbent and if the total amount of contaminants is available to biological receptors or only a fraction of them. This process has a great importance for remediation targets. This question was examined in multi-stage batch sorption and desorption experiments with Trichloroethylene (TCE) and Tetrachloroethylene (also perchloroethylene PCE), as well as o-xylene and p-xylene, in combination with the sorbents activated carbon, charcoal, peat, and the hydrophobic zeolite Y-200. It was shown that the structural composition of the sorbent is one of the important features for a contaminant adsorption-resistant fraction. Hence, the rigid pore system of micro porous zeolite Y-200 exhibits the mostly reversible sorption. Charcoal and activated carbon showed a significantly irreversible sorption, or at least a very slowly desorbing pollutant fraction. This fraction can be harmful in environment due to different kinds of pollutants. Competitive sorption may cause releasing of this fraction.
Generally, the results indicate that the sorption in the above mentioned sorbents for the different chemicals investigated is dominated by pore filling processes, except for peat. A nonlinear type sorption isotherm is described by the combination of the partitioning and pore-filling mechanisms
Assessment the Seasonal Variability and Enrichment of Toxic Trace Metals Pollution in Sediments of Damietta Branch, Nile River, Egypt
No full textThis work appraises the extent of toxic trace metals and seasonal pollution degree in Damietta branch sediments of the River Nile of Egypt. The toxic trace metals Fe, Mn, Cd, Co, Cu, Ni, Pb, and Zn were analysed in sediments from six sites during the summer and winter seasons. The metal concentrations and organic matter were determined using inductively-coupled-plasma mass spectrometry and loss-on-ignition, respectively. Multivariate statistical methods were used in order to allocate the possible metals sources and their relationships in sediments. The seasonal mean sequence of toxic trace metals was: Fe > Mn > Zn > Pb > Cu > Ni > Co > Cd. The mean Cd, Pb, and Zn values exceeded the sediment quality guidelines and average shale and they represent severe potential toxicity for aquatic organisms. Cu and Co were enriched during winter. The geo-accumulation index stipulated that metal pollution degree in the sequence of: Pb > Zn > Cd > Co > Cu > Mn > Ni > Fe. The highest metal pollution index reported in winter in sites S4/S5 and during summer in sites S4–S6. Different agricultural, wastewater discharge, fisheries, and industrial activities, as well as the effect of dilution/concentration during summer/winter seasons, are the main factors that contributed to metal accumulations in Damietta branch sediments. Continuous monitoring and evaluation of toxic trace metal concentrations of the Damietta sediments and similar localities worldwide can help to protect the ecosystem from harmful metal contaminations
Heavy metals seasonal variability and distribution in Lake Qaroun sediments, El-Fayoum, Egypt
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Synthesis, Characterization and Mechanism of MnFe2O4@g-C3N4 Nanocomposite as an effective Photocatalyst for the Generation of Hydrogen and organic contamination degradation
No full textPhotocatalysis has recently been shown to be a good way to get rid of pollutants and produce hydrogen. MnFe2O4@g-C3N4 was synthesized by solid state synthesis technique. In addition to producing hydrogen, MnFe2O4@g-C3N4 demonstrated outstanding photocatalytic performance for the decay of pesticides under visible illumination. The morphology and structure of MnFe2O4@g-C3N4 were approved using Scanning Electron Microscopes (SEM), X-ray diffraction (XRD). Morover, Fourier transform infrared spectroscopy (FT-IR), UV–vis DRS, and surface area (BET). Based on the degradation of the carbaryl contaminant, the photocatalytic action of MnFe2O4@g-C3N4 was evaluated (94%). We for the first time could generate hydrogen by MnFe2O4@g-C3N4 and develop its photocatalytic activities by expanding the surface area and narrowing the band gap value (1.7 eV) and a great surface area of 53.46 m2/g, as displayed by the outcomes
Untersuchungen zur Sorptionsreversibilität von organischen Schadstoffen in Aktivkohle, Holzkohle und Zeolith Y-200
No full textIn einer Vielzahl von Untersuchungen wurde gezeigt, dass die Sorption von organischen Schadstoffen in Böden insbesondere vom organischen Kohlenstoffgehalt (C org) bestimmt wird. Kontrovers wird jedoch die Frage diskutiert, inwieweit Sorptionsprozesse vollständig reversibel sind oder ob eine irreversibel sorbierte Schadstofffraktion in den Sorbenten verbleibt. Dieser Effekt ist etwa bei der Beurteilung von Sanierungsmaßnahmen oder bei der Festlegung von Sanierungszielen von großer Bedeutung. In mehrstufigen Sorptions- und Desorptions-Batch-Versuchen mit TCE und PCE bzw. ortho-Xylol und para-Xylol und den Sorbenten Aktivkohle, Holzkohle sowie einem hydrophobem Zeolith Y-200 wurde diese Fragestellung untersucht. Es konnte gezeigt werden, dass der strukturelle Aufbau des Sorbenten von entscheidender Bedeutung für das Auftreten einer desorptionsresistenten Schadstofffraktion ist. Während für den mikroporösen Zeolith Y-200 mit starrem Porensystem Sorption weitestgehend reversibel ist, wurde für die Holzkohle und die Aktivkohle eine signifikante irreversibel sorbierte, oder zumindest sehr langsam desorbierende Schadstofffraktion ermittelt. Diese Schadstofffraktion kann jedoch bei einem folgenden weiteren Sorptionsschritt durch konkurrierende Sorptionseffekte mobilisiert und freigesetzt werden
Bioremoval of Methylene Blue from Aqueous Solutions by Green Algae (Bracteacoccus sp.) Isolated from North Jordan: Optimization, Kinetic, and Isotherm Studies
No full textAlgae provide an alternative, sustainable, and environmentally beneficial method of dyetreatment. In this study, algae were successfully used to remove methylene blue (MB) from aqueous solutions. The effects of several parameters, such as initial concentration of MB (5–25 mg L−1), algae dosage (0.02–0.1 g mL−1), temperature (4, 20, and 30 °C), and contact time (24, 48, 72 and 84 h), on MB removal were investigated. In addition, the characterization of MB before and after treatment was achieved using UV-spectrophotometer and Liquid chromatography-mass spectrometry (LC-MS). The experimental data were applied to three kinetic models, namely pseudo-first-order, pseudo-second-order, and Elvoich. Moreover, Langmuir, Freundlich, Dubinin–Raduskevich (D–R), and Temkin isotherm models were tested. The maximum removal efficiency of MB (~96%) was accomplished at optimum conditions at the initial concentration of MB (15 mg L−1), temperature (30 °C), and algae dosage (0.06 g mL−1) after 60 min of contact time. The removal of MB follows the pseudo-second-order kinetic model (R2 > 0.999), and the experimental data is best fitted by the Langmuir isotherm model (R2 > 0.9300)
Synthesis of Phase Pure Hexagonal YFeO3 Perovskite as Efficient Visible Light Active Photocatalyst
No full textHexagonal perovskite YFeO3 was synthesized by a complex-assisted sol-gel technique allowing crystallization at calcination temperatures below 700 °C. As determined by diffuse reflectance spectroscopy (DRS) and Tauc plots, the hexagonal YFeO3 exhibits a lower optical band gap (1.81 eV) than the orthorhombic structure (about 2.1 eV or even higher) being typically obtained at elevated temperatures (>700 °C), and thus enables higher visible light photocatalysis activity. Structure and morphology of the synthesized YFeO3 perovskites were analyzed by powder X-ray diffraction (XRD) and nitrogen adsorption, proving that significantly smaller crystallite sizes and higher surface areas are obtained for YFeO3 with a hexagonal phase. The photocatalytic activity of the different YFeO3 phases was deduced via the degradation of the model pollutants methyl orange and 4-chlorophenol. Experiments under illumination with light of different wavelengths, in the presence of different trapping elements, as well as photoelectrochemical tests allow conclusions regarding band positions of YFeO3 and the photocatalytic degradation mechanism. X-ray photoelectron spectroscopy indicates that a very thin layer of Y2O3 might support the photocatalysis by improving the separation of photogenerated charge carriers
