The Experts below are selected from a list of 36084 Experts worldwide ranked by ideXlab platform

Manuel Sastre E De Vicente - One of the best experts on this subject based on the ideXlab platform.

  • Experimental evidences for a new model in the description of the adsorption coupled reduction of cr vi by protonated banana skin
    2013
    Co-Authors: Marta Lopezgarcia, Carlos Reycastro, Calin David, Pablo Lodeiro, Roberto Herrero, José L. Barriada, Manuel Sastre E De Vicente
    Abstract:

    This work reports Experimental evidences, not previously considered, to evaluate the Cr(VI) removal by protonated banana skin biomass. Variations in the number of hydroxyl groups, quantified by potentiometric titrations, and CO2 evolution during Experiments, were attributed mainly to the oxidation of hydroxylic entities present in the studied material. The results indicate that these groups together with the carboxylic moieties are the main functionalities involved on the adsorption-coupled reduction process. The Column Experiment carried out provides a new approach to obtain the maximum reduction capacity of the material (3.72 mmol g?1). Moreover, we hereby propose a model that reports the first evidence for the instant bound of Cr(III) species to the material used, formed after the reduction of Cr(VI) present in solution. The removal process was quantified carrying out Experiments under various pHs, biomass doses and Cr(VI) concentrations, and the mechanism underlying chromium removal was identified.

  • cr vi removal from synthetic and real wastewaters the use of the invasive biomass sargassum muticum in batch and Column Experiments
    2012
    Co-Authors: Marta Lopezgarcia, Pablo Lodeiro, Roberto Herrero, Manuel Sastre E De Vicente
    Abstract:

    Abstract The macroalgae Sargassum muticum was selected for the treatment of solutions containing Cr(VI). Very acidic pH values were established as optimal for Cr(VI) reduction. Algae chemical modification reduced equilibrium time to 4 h. First order kinetic model was used to describe the reduction kinetic of Cr(VI). A Column Experiment allowed to distinguish the processes occurring during Cr(VI) elimination: its reduction to Cr(III) and the subsequent adsorption of this species formed. Under the selected conditions the biomass was capable of reducing all the incoming Cr(VI) during 77 h. Industrial wastewaters from chrome plating industry were also tested for chromium removal.

Christoph Schüth - One of the best experts on this subject based on the ideXlab platform.

  • modelling of geochemical and isotopic changes in a Column Experiment for degradation of tce by zero valent iron
    2008
    Co-Authors: Henning Prommer, Lidia H Aziz, Nerea Bolano, Heinrich Taubald, Christoph Schüth
    Abstract:

    Abstract Zero-valent iron (ZVI) permeable-reactive barriers have become an increasingly used remediation option for the in situ removal of various organic and inorganic chemicals from contaminated groundwater. In the present study a process-based numerical model for the transport and reactions of chlorinated hydrocarbon in the presence of ZVI has been developed and applied to analyse a comprehensive data set from laboratory-scale flow-through Experiments. The model formulation includes a reaction network for the individual sequential and/or parallel transformation of chlorinated hydrocarbons by ZVI, for the resulting geochemical changes such as mineral precipitation, and for the carbon isotope fractionation that occurs during each of the transformation reactions of the organic compounds. The isotopic fractionation was modelled by formulating separate reaction networks for lighter (12C) and heavier (13C) isotopes. The simulation of a Column Experiment involving the parallel degradation of TCE by hydrogenolysis and β-elimination can conclusively reproduce the observed concentration profiles of all collected organic and inorganic data as well as the observed carbon isotope ratios of TCE and its daughter products.

  • tailoring catalysts for hydrodechlorinating chlorinated hydrocarbon contaminants in groundwater
    2000
    Co-Authors: Christoph Schüth, Stephan Disser, Ferdi Schuth, Martin Reinhard
    Abstract:

    Abstract A palladium-on-zeolite catalyst has been optimized for treating groundwater contaminated with halogenated hydrocarbon compounds (HHCs) by hydrodechlorination with dissolved hydrogen. Aqueous sulfite was used as the model poison and the dechlorination of 1,2-dichlorobenzene (1,2-DCB) was used as the model reaction to study the relationship between zeolite hydrophobicity, pore size, and resistance against deactivation. The optimal Pd support is a hydrophobic zeolite Y with a pore size of 0.74 nm tailored to exclude reactive ions from internal sites, to minimize deactivation and inhibition, and to maximize the transformation rate of HHCs. Common halogenated contaminants including chlorinated ethylenes and aromatics are removed within minutes. Catalyst efficiency under groundwater treatment conditions was demonstrated in a bench-scale Column Experiment.

Peter Haglund - One of the best experts on this subject based on the ideXlab platform.

Tobias Licha - One of the best experts on this subject based on the ideXlab platform.

  • influence of a compost layer on the attenuation of 28 selected organic micropollutants under realistic soil aquifer treatment conditions insights from a large scale Column Experiment
    2015
    Co-Authors: Mario Schaffer, Karsten Nodler, Kerrin Franziska Kroger, Carlos Ayora, Jesus Carrera, Marta Hernandez, Tobias Licha
    Abstract:

    Soil aquifer treatment is widely applied to improve the quality of treated wastewater in its reuse as alternative source of water. To gain a deeper understanding of the fate of thereby introduced organic micropollutants, the attenuation of 28 compounds was investigated in Column Experiments using two large scale Column systems in duplicate. The influence of increasing proportions of solid organic matter (0.04% vs. 0.17%) and decreasing redox potentials (denitrification vs. iron reduction) was studied by introducing a layer of compost. Secondary effluent from a wastewater treatment plant was used as water matrix for simulating soil aquifer treatment. For neutral and anionic compounds, sorption generally increases with the compound hydrophobicity and the solid organic matter in the Column system. Organic cations showed the highest attenuation. Among them, breakthroughs were only registered for the cationic beta-blockers atenolol and metoprolol. An enhanced degradation in the Columns with organic infiltration layer was observed for the majority of the compounds, suggesting an improved degradation for higher levels of biodegradable dissolved organic carbon. Solely the degradation of sulfamethoxazole could clearly be attributed to redox effects (when reaching iron reducing conditions). The study provides valuable insights into the attenuation potential for a wide spectrum of organic micropollutants under realistic soil aquifer treatment conditions. Furthermore, the introduction of the compost layer generally showed positive effects on the removal of compounds preferentially degraded under reducing conditions and also increases the residence times in the soil aquifer treatment system via sorption.

  • redox sensitivity and mobility of selected pharmaceutical compounds in a low flow Column Experiment
    2012
    Co-Authors: Stefan Banzhaf, Karsten Nodler, Tobias Licha, Andreas Krein, Traugott Scheytt
    Abstract:

    Abstract In this study a laboratory Column Experiment under water saturated conditions was conducted to investigate the transport behaviour of the pharmaceutical compounds sulfamethoxazole, carbamazepine, diclofenac, and ibuprofen under varying nitrate concentrations. Organic rich sediment (f OC  = 0.01) and surface water from a formerly investigated field site were used. The water was spiked with the four compounds and the specific redox conditions in the Column (0.351 m height) were varied throughout the Experiment by adding nitrate in the influent water. Stepwise controlled decreasing influent nitrate concentrations between 131 and 20 mg L − 1 were applied in the course of the Experiment which lasted 71 days. This established temporarily denitrifying conditions in the Column during the reduction of nitrate. Sulfamethoxazole was severely influenced by this process. During denitrification sulfamethoxazole concentrations in the effluent water decreased rapidly and significantly. This Experiment demonstrates the strong dependency of sulfamethoxazole transformation specifically on nitrate reducing redox conditions and therefore may help to explain the wide ranges of reported degradability for this compound. Ibuprofen was more stable under denitrifying redox conditions. Both for carbamazepine and diclofenac apparent retardation was observed. For carbamazepine this was attributed to sorption and also to degradation. For diclofenac nitrate controlled degradation seems the dominating process for the apparent retardation of this compound.

David P Hamilto - One of the best experts on this subject based on the ideXlab platform.

  • combating hypoxia anoxia at sediment water interfaces a preliminary study of oxygen nanobubble modified clay materials
    2018
    Co-Authors: Honggang Zhang, Lei I, Grant Wayne Tempero, Tao Lyu, David P Hamilto
    Abstract:

    Abstract Combating hypoxia/anoxia is an increasingly common need for restoring natural waters suffering from eutrophication. Oxygen nanobubble modified natural particles were investigated for mitigating hypoxia/anoxia at the sediment-water interface (SWI) in a simulated Column Experiment. By adding oxygen nanobubble modified zeolites (ONMZ) and local soils (ONMS), the oxygen nanobubble concentrations (105–107 particles/mL) were several orders of magnitude higher in the water than the original water solution (104 particles/mL) within 24 h. In the Column Experiment, an oxygen-locking surface sediment layer was formed after capping with ONMZ and ONMS particles. The synergy of diffusion of oxygen nanobubbles and retention of oxygen in this layer contributes to both the increase of DO and reversal of hypoxic conditions. The overlying water had significantly higher dissolved oxygen (DO) values (4–7.5 mg/L) over the Experimental period of 127 days in ONMZ and ONMS compared with the control systems (around 1 mg/L). Moreover, the oxidation-reduction potential (ORP) was reversed from −200 mV to 180–210 mV and maintained positive values for 89 days in ONMZ systems. In the control systems, ORP was consistently negative and decreased from −200 mV to −350 mV. The total phosphorus (TP) flux from sediment to water across the SWI was negative in the ONMZ and ONMS treated systems, but positive in the control system, indicating the sediment could be switched from TP source to sink. The oxygen-locking capping layer was crucial in preventing oxygen consumption caused by the reduced substances released from the anoxic sediment. The study outlines a potentially promising technology for mitigating sediment anoxia and controlling nutrient release from sediments, which could contribute significantly to addressing eutrophication and ecological restoration.

  • Combating hypoxia/anoxia at sediment-water interfaces: a preliminary study of oxygen nanobubble modified clay materials
    2018
    Co-Authors: Zhang H., Lyu T, David P Hamilto, I L, Tempero G, Pa G
    Abstract:

    Combating hypoxia/anoxia is an increasingly common need for restoring natural waters suffering from eutrophication. Oxygen nanobubble modified natural particles were investigated for mitigating hypoxia/anoxia at the sediment-water interface (SWI) in a simulated Column Experiment. By adding oxygen nanobubble modified zeolites (ONMZ) and local soils (ONMS), the oxygen nanobubble concentrations (105–107 particles/mL) were several orders of magnitude higher in the water than the original water solution (104 particles/mL) within 24 h. In the Column Experiment, an oxygen-locking surface sediment layer was formed after capping with ONMZ and ONMS particles. The synergy of diffusion of oxygen nanobubbles and retention of oxygen in this layer contributes to both the increase of DO and reversal of hypoxic conditions. The overlying water had significantly higher dissolved oxygen (DO) values (4–7.5 mg/L) over the Experimental period of 127 days in ONMZ and ONMS compared with the control systems (around 1 mg/L). Moreover, the oxidation-reduction potential (ORP) was reversed from −200 mV to 180–210 mV and maintained positive values for 89 days in ONMZ systems. In the control systems, ORP was consistently negative and decreased from −200 mV to −350 mV. The total phosphorus (TP) flux from sediment to water across the SWI was negative in the ONMZ and ONMS treated systems, but positive in the control system, indicating the sediment could be switched from TP source to sink. The oxygen-locking capping layer was crucial in preventing oxygen consumption caused by the reduced substances released from the anoxic sediment. The study outlines a potentially promising technology for mitigating sediment anoxia and controlling nutrient release from sediments, which could contribute significantly to addressing eutrophication and ecological restoration