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Auflistung Aufsätze nach Schlagwort "Adsorption"

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    Veröffentlichung
    Biogenic amorphous ferric hydroxide as adsorbent for vanadium removal in drinking water production
    (2023) Dippon-Deissler, Urs; Mahringer, Daniel; Ruhl, Aki Sebastian; Zerelli, Sami Sofiene
    Vanadium as toxic heavy metal is a drinking water relevant contaminant. However, there is a lack in treatment processes to meet regulatory requirements (e.g. 4 g l-1 in Germany). This study introduces a novel treatment process - the vanadium adsorption onto biogenic amorphous ferric hydroxide (AFH). Basic mechanisms of adsorption onto AFH are described and compared to granular ferric hydroxide (GFH). Adsorption kinetics and pH dependent isotherms in drinking and ultrapure water, parametrization via the empirical Freundlich and Langmuir models, and bond type and strength assessments via sequential extraction are presented. AFH was generated in pilot waterworks in which Fe(II) and oxygen were dosed and subsequently Fe(II) microbiologically oxidized and precipitated in the filter bed. The backwash-water was collected and used for adsorption experiments. Sequential extraction was executed with vanadium loaded AFH produced in the pilot plant. AFH is identified as alternative adsorbent to GFH with similar affinity and capacity. The isotherms cover a concentration range from 10 g l-1 to 4 mg l-1 and the Freundlich model showed a better fit with the experimental data than the Langmuir model. A bidentate mononuclear inner sphere complex is assumed for vanadium adsorption onto AFH, while a bidentate binuclear inner sphere complex is expected for GFH. Sequential extraction showed a strong bond between AFH and vanadium, which was only mobilized by the last extraction step the dissolution of iron particles. A treatment process - adsorption onto biogenic AFH - is suitable for effective vanadium removal and should be further investigated for technical implementation. © 2023 The Author(s).
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    Veröffentlichung
    Characterization of activated carbons for water treatment using TGA-FTIR for analysis of oxygen-containing functional groups
    (2022) Dittmann, Daniel; Zietzschmann, Frederik; Ruhl, Aki Sebastian; Schumann, Pia; Saal, Leon; Braun, Ulrike
    Water treatment with activated carbon (AC) is an established method for the removal of organic micropollutants and natural organic matter. However, it is not yet possible to predict the removal of individual pollutants. An appropriate material characterization, matching adsorption processes in water, might be the missing piece in the puzzle. To this end, this study examined 25 different commercially available ACs to evaluate their material properties. Frequently reported analyses, including N2 adsorption/desorption, CHNS(O), point of zero charge (PZC) analysis, and X-ray photoelectron spectroscopy (XPS) were conducted on a selected subset of powdered ACs. Inorganic elements examined using X-ray fluorescence (XRF) and X-ray iffraction spectroscopy (XRD) revealed that relative elemental contents were distinctive to the individual AC's raw material and activation procedure. This study also is the first to use thermogravimetric analysis (TGA) coupled to Fourier-transform infrared spectroscopy (FTIR) to conduct quantitative analyses of functional surface oxygen groups (SOGs: carboxylic acid, anhydride, lactone, phenol, carbonyl, and pyrone groups) on such a large number of ACs. The comparably economical TGA provides a surrogate for the PZC, the oxygen and carbon content, as well as mass loss profiles that depict the AC's chemistry. Furthermore, we found that SOG contents determined by TGA-FTIR covered a wide individual range and depended on the raw material of the AC. Surface chemistry might therefore provide an indication of the suitability of a particular AC for a variety of target substances in different target waters. TGA and TGA-FTIR can help practitioners to control AC use in waterworks or wastewater treatment plants.
  • Vorschaubild nicht verfügbar
    Veröffentlichung
    Fast empirical lab method for performance projections of large-scale powdered activated carbon re-circulation plants
    (2019) Zietzschmann, Frederik; Dittmar, Stefan; Ruhl, Aki Sebastian
    Powdered activated carbon (PAC) for organic micro-pollutant (OMP) removal can be applied effectively on wastewater treatment plant (WWTP) effluents by using recirculation schemes, accumulating the PAC in the system. This technique is complex because several factors are unknown: (i) the PAC concentration in the system, (ii) specific and average contact times of PAC particles, and (iii) PAC particle loadings with target compounds/competing water constituents. Thus, performance projections (e.g. in the lab) are very challenging. We sampled large-scale PAC plants with PAC sludge recirculation on eight different WWTPs. The PAC plant-induced OMP removals were notably different, even when considering PAC concentrations in proportion to background organic sum parameters. The variability is likely caused by differing PAC products, varying water composition, differently effective plant/recirculation operation, and variable biodegradation. Plant PAC samples and parts of the PAC plant influent samples were used in laboratory tests, applying multiples (0.5, 1, 2, 4) of the respective large-scale "fresh" PAC doses, and several fixed contact times (0.5, 1, 2, 4, 48 h). The aim was to empirically identify suitable combinations of lab PAC dose (as multiples of the plant PAC dose) and contact time, which represent the PAC plant performances in removing OMPs (for specific OMPs at single locations, and for averages of different OMPs at all locations). E.g., for five well adsorbing, little biodegradable OMPs, plant performances can be projected by using a lab PAC dose of twice the respective full-scale PAC dose and 4 h lab contact time (standard deviation of 13 %-points). © 2018 Elsevier Ltd. All rights reserved.